1.
Oceanography
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Oceanography, also known as oceanology, is the study of the physical and the biological aspects of the ocean. Paleoceanography studies the history of the oceans in the geologic past, humans first acquired knowledge of the waves and currents of the seas and oceans in pre-historic times. Observations on tides were recorded by Aristotle and Strabo, early exploration of the oceans was primarily for cartography and mainly limited to its surfaces and of the animals that fishermen brought up in nets, though depth soundings by lead line were taken. Although Juan Ponce de León in 1513 first identified the Gulf Stream, Franklin measured water temperatures during several Atlantic crossings and correctly explained the Gulf Streams cause. Franklin and Timothy Folger printed the first map of the Gulf Stream in 1769-1770, information on the currents of the Pacific Ocean was gathered by explorers of the late 18th century, including James Cook and Louis Antoine de Bougainville. James Rennell wrote the first scientific textbooks on oceanography, detailing the current flows of the Atlantic, during a voyage around the Cape of Good Hope in 1777, he mapped the banks and currents at the Lagullas. He was also the first to understand the nature of the intermittent current near the Isles of Scilly, Robert FitzRoy published a four-volume report of the Beagles three voyages. In 1841–1842 Edward Forbes undertook dredging in the Aegean Sea that founded marine ecology, the first superintendent of the United States Naval Observatory, Matthew Fontaine Maury devoted his time to the study of marine meteorology, navigation, and charting prevailing winds and currents. His 1855 textbook Physical Geography of the Sea was one of the first comprehensive oceanography studies, many nations sent oceanographic observations to Maury at the Naval Observatory, where he and his colleagues evaluated the information and distributed the results worldwide. Despite all this, human knowledge of the oceans remained confined to the topmost few fathoms of the water, almost nothing was known of the ocean depths. The Royal Navys efforts to all of the worlds coastlines in the mid-19th century reinforced the vague idea that most of the ocean was very deep. As exploration ignited both popular and scientific interest in the regions and Africa, so too did the mysteries of the unexplored oceans. The seminal event in the founding of the science of oceanography was the 1872-76 Challenger expedition. As the first true oceanographic cruise, this laid the groundwork for an entire academic. In response to a recommendation from the Royal Society, The British Government announced in 1871 an expedition to explore worlds oceans, charles Wyville Thompson and Sir John Murray launched the Challenger expedition. The Challenger, leased from the Royal Navy, was modified for scientific work, under the scientific supervision of Thomson, Challenger travelled nearly 70,000 nautical miles surveying and exploring. On her journey circumnavigating the globe,492 deep sea soundings,133 bottom dredges,151 open water trawls and 263 serial water temperature observations were taken, around 4,700 new species of marine life were discovered. The result was the Report Of The Scientific Results of the Exploring Voyage of H. M. S, Murray, who supervised the publication, described the report as the greatest advance in the knowledge of our planet since the celebrated discoveries of the fifteenth and sixteenth centuries
2.
Ocean current
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Depth contours, shoreline configurations, and interactions with other currents influence a currents direction and strength. Therefore ocean currents are primarily horizontal water movements, Ocean currents flow for great distances, and together, create the global conveyor belt which plays a dominant role in determining the climate of many of the Earth’s regions. More specifically, ocean currents influence the temperature of the regions through which they travel, for example, warm currents traveling along more temperate coasts increase the temperature of the area by warming the sea breezes that blow over them. Perhaps the most striking example is the Gulf Stream, which makes northwest Europe much more temperate than any region at the same latitude. Another example is Lima, Peru where the climate is cooler than the tropical latitudes in which the area is located, in these wind driven currents, the Ekman spiral effect results in the currents flowing at an angle to the driving winds. In addition, the areas of ocean currents move somewhat with the seasons. Deep ocean basins generally have a surface current, in that the eastern equatorward-flowing branch is broad. These western boundary currents are a consequence of the rotation of the Earth, Deep ocean currents are driven by density and temperature gradients. Thermohaline circulation is known as the oceans conveyor belt. These currents, called submarine rivers, flow under the surface of the ocean and are hidden from immediate detection, where significant vertical movement of ocean currents is observed, this is known as upwelling and downwelling. Deep ocean currents are currently being researched using a fleet of robots called Argo. The South Equatorial Currents of the Atlantic and Pacific straddle the equator, though the Coriolis effect is weak near the equator, water moving in the currents on either side of the equator is deflected slightly poleward and replaced by deeper water. Thus, equatorial upwelling occurs in these westward flowing equatorial surface currents, upwelling is an important process because this water from within and below the pycnocline is often rich in nutrients and greatly benefits the growth of marine organisms. By contrast, generally poor conditions for growth prevail in most of the tropical ocean because strong layering isolates deep. Ocean currents are measured in sverdrup, where 1 sv is equivalent to a flow rate of 1,000,000 m3 per second. Surface currents are found on the surface of an ocean, and are driven by large scale wind currents and they are directly affected by the wind—the Coriolis effect plays a role in their behaviors. Horizontal and vertical currents also exist below the pycnocline in the deeper waters. The movement of water due to differences in density as a function of water temperature, ripple marks in sediments, scour lines, and the erosion of rocky outcrops on deep-ocean floors are evidence that relatively strong, localized bottom currents exist
3.
Wind
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Wind is the flow of gases on a large scale. On the surface of the Earth, wind consists of the movement of air. Winds are commonly classified by their scale, their speed, the types of forces that cause them, the regions in which they occur. The strongest observed winds on a planet in the Solar System occur on Neptune, Winds have various aspects, an important one being its velocity, another the density of the gas involved, another its energy content or wind energy. In meteorology, winds are referred to according to their strength. Short bursts of high speed wind are termed gusts, strong winds of intermediate duration are termed squalls. Long-duration winds have various names associated with their strength, such as breeze, gale, storm. The two main causes of large-scale atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet, within the tropics, thermal low circulations over terrain and high plateaus can drive monsoon circulations. In coastal areas the sea breeze/land breeze cycle can define local winds, in areas that have variable terrain, mountain, Wind powers the voyages of sailing ships across Earths oceans. Hot air balloons use the wind to take trips, and powered flight uses it to increase lift. Areas of wind caused by various weather phenomena can lead to dangerous situations for aircraft. When winds become strong, trees and man-made structures are damaged or destroyed, Winds can shape landforms, via a variety of aeolian processes such as the formation of fertile soils, such as loess, and by erosion. Wind also affects the spread of wildfires, Winds can disperse seeds from various plants, enabling the survival and dispersal of those plant species, as well as flying insect populations. When combined with temperatures, wind has a negative impact on livestock. Wind affects animals food stores, as well as their hunting, Wind is caused by differences in the atmospheric pressure. When a difference in atmospheric pressure exists, air moves from the higher to the pressure area. On a rotating planet, air will also be deflected by the Coriolis effect, globally, the two major driving factors of large-scale wind patterns are the differential heating between the equator and the poles and the rotation of the planet. Outside the tropics and aloft from frictional effects of the surface, near the Earths surface, friction causes the wind to be slower than it would be otherwise
4.
Coriolis force
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In physics, the Coriolis force is an inertial force that acts on objects that are in motion relative to a rotating reference frame. In a reference frame with clockwise rotation, the acts to the left of the motion of the object. In one with anticlockwise rotation, the acts to the right. Early in the 20th century, the term Coriolis force began to be used in connection with meteorology, deflection of an object due to the Coriolis force is called the Coriolis effect. Newtons laws of motion describe the motion of an object in a frame of reference. When Newtons laws are transformed to a frame of reference. Both forces are proportional to the mass of the object, the Coriolis force is proportional to the rotation rate and the centrifugal force is proportional to its square. The Coriolis force acts in a perpendicular to the rotation axis. The centrifugal force acts outwards in the direction and is proportional to the distance of the body from the axis of the rotating frame. These additional forces are termed inertial forces, fictitious forces or pseudo forces and they allow the application of Newtons laws to a rotating system. They are correction factors that do not exist in a non-accelerating or inertial reference frame, a commonly encountered rotating reference frame is the Earth. The Coriolis effect is caused by the rotation of the Earth, such motions are constrained by the surface of the Earth, so only the horizontal component of the Coriolis force is generally important. This force causes moving objects on the surface of the Earth to be deflected to the right in the Northern Hemisphere, the horizontal deflection effect is greater near the poles, since the effective rotation rate about a local vertical axis is largest there, and smallest at the equator. This effect is responsible for the rotation of large cyclones, riccioli, Grimaldi, and Dechales all described the effect as part of an argument against the heliocentric system of Copernicus. In other words, they argued that the Earths rotation should create the effect, the effect was described in the tidal equations of Pierre-Simon Laplace in 1778. Gaspard-Gustave Coriolis published a paper in 1835 on the yield of machines with rotating parts. That paper considered the forces that are detected in a rotating frame of reference. Coriolis divided these forces into two categories
5.
Vorticity
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Conceptually, vorticity could be determined by marking the part of continuum in a small neighborhood of the point in question, and watching their relative displacements as they move along the flow. The vorticity vector would be twice the angular velocity vector of those particles relative to their center of mass. This quantity must not be confused with the velocity of the particles relative to some other point. More precisely, the vorticity is a pseudovector field ω→, defined as the curl of the flow velocity u→ vector, the definition can be expressed by the vector analysis formula, ω → ≡ ∇ × u →, where ∇ is the del operator. The vorticity of a flow is always perpendicular to the plane of the flow. The vorticity is related to the flows circulation along a path by the Stokes theorem. Namely, for any infinitesimal surface element C with normal direction n→ and area dA, many phenomena, such as the blowing out of a candle by a puff of air, are more readily explained in terms of vorticity rather than the basic concepts of pressure and velocity. This applies, in particular, to the formation and motion of vortex rings, in a mass of continuum that is rotating like a rigid body, the vorticity is twice the angular velocity vector of that rotation. This is the case, for example, of water in a tank that has been spinning for a while around its vertical axis, the vorticity may be nonzero even when all particles are flowing along straight and parallel pathlines, if there is shear. The vorticity will be zero on the axis, and maximum near the walls, conversely, a flow may have zero vorticity even though its particles travel along curved trajectories. An example is the ideal irrotational vortex, where most particles rotate about some straight axis, another way to visualize vorticity is to imagine that, instantaneously, a tiny part of the continuum becomes solid and the rest of the flow disappears. If that tiny new solid particle is rotating, rather than just moving with the flow, mathematically, the vorticity of a three-dimensional flow is a pseudovector field, usually denoted by ω→, defined as the curl or rotational of the velocity field v→ describing the continuum motion. In Cartesian coordinates, ω → = ∇ × v → = × = In words, the evolution of the vorticity field in time is described by the vorticity equation, which can be derived from the Navier–Stokes equations. This is clearly true in the case of 2-D potential flow, Vorticity is a useful tool to understand how the ideal potential flow solutions can be perturbed to model real flows. In general, the presence of viscosity causes a diffusion of vorticity away from the vortex cores into the flow field. This flow is accounted for by the term in the vorticity transport equation. Thus, in cases of very viscous flows, the vorticity will be diffused throughout the flow field, a vortex line or vorticity line is a line which is everywhere tangent to the local vorticity vector. Vortex lines are defined by the relation d x ω x = d y ω y = d z ω z, a vortex tube is the surface in the continuum formed by all vortex-lines passing through a given closed curve in the continuum
6.
Curl (mathematics)
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In vector calculus, the curl is a vector operator that describes the infinitesimal rotation of a 3-dimensional vector field. At every point in the field, the curl of that point is represented by a vector, the attributes of this vector characterize the rotation at that point. The direction of the curl is the axis of rotation, as determined by the rule. If the vector represents the flow velocity of a moving fluid. A vector field whose curl is zero is called irrotational, the curl is a form of differentiation for vector fields. The alternative terminology rotor or rotational and alternative notations rot F and ∇ × F are often used for curl F and this is a similar phenomenon as in the 3 dimensional cross product, and the connection is reflected in the notation ∇ × for the curl. The name curl was first suggested by James Clerk Maxwell in 1871, the curl of a vector field F, denoted by curl F, or ∇ × F, or rot F, at a point is defined in terms of its projection onto various lines through the point. As such, the curl operator maps continuously differentiable functions f, ℝ3 → ℝ3 to continuous functions g, in fact, it maps Ck functions in ℝ3 to Ck −1 functions in ℝ3. Implicitly, curl is defined by, ⋅ n ^ = d e f lim A →0 where ∮C F · dr is a line integral along the boundary of the area in question, and | A | is the magnitude of the area. Note that the equation for each component, k can be obtained by exchanging each occurrence of a subscript 1,2,3 in cyclic permutation, 1→2, 2→3, and 3→1. If are the Cartesian coordinates and are the coordinates, then h i =2 +2 +2 is the length of the coordinate vector corresponding to ui. The remaining two components of curl result from cyclic permutation of indices,3,1,2 →1,2,3 →2,3,1. Suppose the vector field describes the velocity field of a fluid flow, if the ball has a rough surface, the fluid flowing past it will make it rotate. The rotation axis points in the direction of the curl of the field at the centre of the ball, and the angular speed of the rotation is half the magnitude of the curl at this point. The notation ∇ × F has its origins in the similarities to the 3-dimensional cross product, such notation involving operators is common in physics and algebra. However, in coordinate systems, such as polar-toroidal coordinates. This expands as follows, i + j + k Although expressed in terms of coordinates, equivalently, = e k ε k l m ∇ l F m where ek are the coordinate vector fields. Equivalently, using the derivative, the curl can be expressed as, ∇ × F = ♯ Here ♭ and ♯ are the musical isomorphisms
7.
Torque
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Torque, moment, or moment of force is rotational force. Just as a force is a push or a pull. Loosely speaking, torque is a measure of the force on an object such as a bolt or a flywheel. For example, pushing or pulling the handle of a wrench connected to a nut or bolt produces a torque that loosens or tightens the nut or bolt, the symbol for torque is typically τ, the lowercase Greek letter tau. When it is called moment of force, it is denoted by M. The SI unit for torque is the newton metre, for more on the units of torque, see Units. This article follows US physics terminology in its use of the word torque, in the UK and in US mechanical engineering, this is called moment of force, usually shortened to moment. In US physics and UK physics terminology these terms are interchangeable, unlike in US mechanical engineering, Torque is defined mathematically as the rate of change of angular momentum of an object. The definition of states that one or both of the angular velocity or the moment of inertia of an object are changing. Moment is the term used for the tendency of one or more applied forces to rotate an object about an axis. For example, a force applied to a shaft causing acceleration, such as a drill bit accelerating from rest. By contrast, a force on a beam produces a moment, but since the angular momentum of the beam is not changing. Similarly with any force couple on an object that has no change to its angular momentum and this article follows the US physics terminology by calling all moments by the term torque, whether or not they cause the angular momentum of an object to change. The concept of torque, also called moment or couple, originated with the studies of Archimedes on levers, the term torque was apparently introduced into English scientific literature by James Thomson, the brother of Lord Kelvin, in 1884. A force applied at an angle to a lever multiplied by its distance from the levers fulcrum is its torque. A force of three newtons applied two metres from the fulcrum, for example, exerts the same torque as a force of one newton applied six metres from the fulcrum. More generally, the torque on a particle can be defined as the product, τ = r × F, where r is the particles position vector relative to the fulcrum. Alternatively, τ = r F ⊥, where F⊥ is the amount of force directed perpendicularly to the position of the particle, any force directed parallel to the particles position vector does not produce a torque
8.
Vortex
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In fluid dynamics, a vortex is a region in a fluid in which the flow rotates around an axis line, which may be straight or curved. The plural of vortex is either vortices or vortexes, vortices form in stirred fluids, and may be observed in phenomena such as smoke rings, whirlpools in the wake of boat, or the winds surrounding a tornado or dust devil. Vortices are a component of turbulent flow. The distribution of velocity, vorticity, as well as the concept of circulation are used to characterize vortices, in most vortices, the fluid flow velocity is greatest next to its axis and decreases in inverse proportion to the distance from the axis. Once formed, vortices can move, stretch, twist, a moving vortex carries with it some angular and linear momentum, energy, and mass. A key concept in the dynamics of vortices is the vorticity, conceptually, the vorticity could be observed by placing a tiny rough ball at the point in question, free to move with the fluid, and observing how it rotates about its center. The direction of the vorticity vector is defined to be the direction of the axis of rotation of this imaginary ball while its length is twice the angular velocity. The local rotation measured by the vorticity ω → must not be confused with the velocity vector of that portion of the fluid with respect to the external environment or to any fixed axis. In a vortex, in particular, ω → may be opposite to the angular velocity vector of the fluid relative to the vortexs axis. In theory, the u of the particles in a vortex may vary with the distance r from the axis in many ways. Ω → =, r → =, u → = Ω → × r → =, ω → = ∇ × u → = =2 Ω →. In this case the vorticity ω → is zero at any point not on that axis, Ω → =, r → =, u → = Ω → × r → =, ω → = ∇ × u → =0. In the absence of forces, a vortex usually evolves fairly quickly toward the irrotational flow pattern. Irrotational vortices are also called free vortices, for an irrotational vortex, the circulation is zero along any closed contour that does not enclose the vortex axis, and has a fixed value, Γ, for any contour that does enclose the axis once. The tangential component of the velocity is then u θ = Γ2 π r. The angular momentum per unit mass relative to the axis is therefore constant. However, the ideal irrotational vortex flow is not physically realizable, indeed, in real vortices there is always a core region surrounding the axis where the particle velocity stops increasing and then decreases to zero as r goes to zero. Within that region, the flow is no longer irrotational, the vorticity ω → becomes non-zero, the Rankine vortex is a model that assumes a rigid-body rotational flow where r is less than a fixed distance r0, and irrotational flow outside that core regions
9.
Atmosphere of Earth
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The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earths gravity. The atmosphere of Earth protects life on Earth by absorbing solar radiation, warming the surface through heat retention. By volume, dry air contains 78. 09% nitrogen,20. 95% oxygen,0. 93% argon,0. 04% carbon dioxide, and small amounts of other gases. Air also contains an amount of water vapor, on average around 1% at sea level. The atmosphere has a mass of about 5. 15×1018 kg, the atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km, or 1. 57% of Earths radius, is used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km, several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earths atmosphere and its processes is called atmospheric science, early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The three major constituents of air, and therefore of Earths atmosphere, are nitrogen, oxygen, water vapor accounts for roughly 0. 25% of the atmosphere by mass. The remaining gases are often referred to as gases, among which are the greenhouse gases, principally carbon dioxide, methane, nitrous oxide. Filtered air includes trace amounts of other chemical compounds. Various industrial pollutants also may be present as gases or aerosols, such as chlorine, fluorine compounds, sulfur compounds such as hydrogen sulfide and sulfur dioxide may be derived from natural sources or from industrial air pollution. In general, air pressure and density decrease with altitude in the atmosphere, however, temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions. In this way, Earths atmosphere can be divided into five main layers, excluding the exosphere, Earth has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. It extends from the exobase, which is located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km where it merges into the solar wind. This layer is composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen. The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another, thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind, the exosphere is located too far above Earth for any meteorological phenomena to be possible
10.
Ocean
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An ocean is a body of saline water that composes much of a planets hydrosphere. On Earth, an ocean is one of the major divisions of the World Ocean. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern, the word sea is often used interchangeably with ocean in American English but, strictly speaking, a sea is a body of saline water partly or fully enclosed by land. The ocean contains 97% of Earths water, and oceanographers have stated that less than 5% of the World Ocean has been explored, the total volume is approximately 1.35 billion cubic kilometers with an average depth of nearly 3,700 meters. As the world ocean is the component of Earths hydrosphere, it is integral to all known life, forms part of the carbon cycle. The world ocean is the habitat of 230,000 known species, but because much of it is unexplored, the origin of Earths oceans remains unknown, oceans are thought to have formed in the Hadean period and may have been the impetus for the emergence of life. Extraterrestrial oceans may be composed of water or other elements and compounds, the only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, although there is evidence for the existence of oceans elsewhere in the Solar System. Early in their histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, compounds such as salts and ammonia dissolved in water lower its freezing point so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many planets and natural satellites, notably. The Solar Systems giant planets are thought to have liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of water within a circumstellar habitable zone. Ocean planets are a type of planet with a surface completely covered with liquid. The concept of Ōkeanós has an Indo-European connection, Greek Ōkeanós has been compared to the Vedic epithet ā-śáyāna-, predicated of the dragon Vṛtra-, who captured the cows/rivers. Related to this notion, the Okeanos is represented with a dragon-tail on some early Greek vases, though generally described as several separate oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the World Ocean or global ocean. This concept of a body of water with relatively free interchange among its parts is of fundamental importance to oceanography. The major oceanic divisions – listed below in descending order of area and volume – are defined in part by the continents, various archipelagos, Oceans are fringed by smaller, adjoining bodies of water such as seas, gulfs, bays, bights, and straits. The Mid-Oceanic Ridge of the World are connected and form the Ocean Ridge, the continuous mountain range is 65,000 km long, and the total length of the oceanic ridge system is 80,000 km long
11.
Indian Ocean Gyre
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The Indian Ocean gyre, located in the Indian Ocean, is one of the five major oceanic gyres, large systems of rotating ocean currents, which together form the backbone of the global conveyer belt. The Indian Ocean gyre is composed of two currents, the South Equatorial Current, and the West Australian Current. Normally moving counter-clockwise, in the winter the Indian Ocean gyre reverses direction due to the winds of the South Asian Monsoon. In the summer, the land is warmer than the ocean, however, during the winter, these temperatures reverse, making the winds blow from the land to the ocean. Because most of the air pressure gradient is retained behind the Tibetan plateau, air pressure gradients over the Indian Ocean and this results in winds of moderate strength, due to the protection from the full force winds blowing off the Mongolian high pressure region. Because of these moderate, dry winds, the Winter Monsoon season in the Indian Ocean region is the dry season for most of Southern Asia. Due to this seasonal wind cycle, the currents of the Indian Ocean, like the other gyres, it contains a garbage patch. A garbage patch is a region of marine debris within the water column that circulate the gyre constantly. The Indian Ocean’s garbage patch covers an area, at least five million square kilometers. As garbage patches such as these circulate for long periods of time, in the Indian Ocean gyre, the garbage patch has been more of a mystery. Having just been discovered in 2010, it is still under research and it is known, however, that like most garbage patches, it is very fluid, and changes with the seasons, making its location difficult to pinpoint. It seems to circulate with the Indian Ocean gyre, from the Australian side to the African side, down the African coast, and then back to Australia. According to the team who discovered the garbage patch, the rotation of the gyre’s garbage patch takes about six years, until it reaches the center of the gyre
12.
North Atlantic Gyre
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The North Atlantic Gyre, located in the Atlantic Ocean, is one of the five major oceanic gyres. This gyre is similar to the North Pacific Gyre in the way it traps man-made marine debris in the North Atlantic Garbage Patch, the North Atlantic Gyre forms the Sargasso Sea, noted for its still waters and dense seaweed accumulations. As with many patterns, the North Atlantic Gyre experiences seasonal changes. Stramma and Siedler determined that the gyre expands and contracts with a variance, however. During the Northern Hemisphere winter season, the gyre follows a more zonal pattern, as the seasons move from winter to summer, the gyre shifts south by a few degrees latitude. This occurs concurrently with the displacement of the part of the gyre. It has been concluded that zonal deviations within the gyre remain small while north and south of the gyre they are large. Data collected in the Sargasso Sea region in the part of the North Atlantic Gyre has led to analytical evidence that the variability of this gyre is linked to wintertime convective mixing. According to Bates, a variation of 8-10 °C in surface temperature occurs alongside a fluctuation in the mixed layer depth between the Northern Hemisphere winter and summer seasons. The depth rises from 200 meters in winter to about 10 meters in summer, nutrients remain below the euphotic zone for most of the year, resulting in low primary production. Yet during winter convective mixing, nutrients penetrate the euphotic zone and this then lifts the mixed-layer depth to 10 meters. The changes in oceanic biology and vertical mixing between winter and summer in the North Atlantic Gyre seasonally alter the amount of carbon dioxide in the seawater. Interannual trends have established that carbon dioxide concentrations within this gyre are increasing at a rate to that occurring in the atmosphere. This discovery concurs with that made in the North Pacific Gyre, the North Atlantic Gyre also undergoes temperature changes via atmospheric wave patterns. The North Atlantic Oscillation is one such pattern, during its positive phase, the gyre warms. This is due to a weakening of the winds, resulting in reduced wind stress and heat exchange. Collections of aerosols, marine particles, and ocean water in the North Atlantic Gyre from 1990-1992 have led to measurements in lead isotope ratios, the surface layers of the Sargasso Sea were used to estimate the lead isotopic concentrations. 42-57% of the lead isotope concentrations result from American industrial and automotive contamination, despite the reduction in the production, however, lead concentrations from measurements made after 1992 show a decrease in the amount of lead contamination
13.
North Pacific Gyre
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The North Pacific Gyre, located in the northern Pacific Ocean, is one of the five major oceanic gyres. This gyre covers most of the northern Pacific Ocean and it is the largest ecosystem on Earth, located between the equator and 50° N latitude, and comprising 20 million square kilometers. It is the site of an unusually intense collection of marine debris. Ecosystem of the North Pacific Subtropical Gyre North Atlantic Garbage Patch Great Pacific Garbage Patch Ocean current Marine Pollution South Atlantic Gyre Ocean currents
14.
South Atlantic Gyre
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The South Atlantic Gyre is the subtropical gyre in the south Atlantic Ocean. In the southern portion of the gyre, northwesterly winds drive eastward-flowing currents that are difficult to distinguish from the boundary of the Antarctic Circumpolar Current. Like other oceanic gyres, it collects vast amounts of floating debris, South of this gyre is the Antarctic Circumpolar Current. This current flows from West to East around Antarctica, another name for this current is the West Wind Drift. This current allows Antarctica to maintain its huge ice sheet by keeping warm ocean waters away, at approximately 125 Sv, this current is the largest ocean current. The Brazil Current is the western boundary current of the gyre and it flows south along the Brazilian coast to the Rio de la Plata. The current is considerably weaker than its North Atlantic counterpart, the Gulf Stream, Ocean current Volta do mar Ocean currents Ocean currents
15.
South Pacific Gyre
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The center of the South Pacific Gyre is the site on Earth farthest from any continents and productive ocean regions and is regarded as Earth’s largest oceanic desert. Earth’s trade winds and Coriolis force cause the ocean currents in South Pacific Ocean to circulate counter clockwise, the low levels of biogenic and eolian deposition cause sediments to accumulate on the ocean floor very slowly. In the center of the South Pacific Gyre, the rate is 0.1 to 1 m per million years. The sediment thickness ranges from 1 to 70m, with thinner sediments occurring closer to the center of the Gyre, the low flux of particles to the South Pacific Gyre cause the water there to be the clearest seawater in the world. Beneath the seafloor, the sediments and surrounding porewaters contain an unusual subseafloor biosphere. Despite extremely low amounts of buried organic material, microbes live throughout the sediment column. Average cell abundances and net rates of respiration are a few orders of magnitude lower than any other subseafloor biosphere previously studied, the South Pacific Gyre subseafloor community is also unusual because it contains oxygen throughout the entire sediment column. In other subseafloor biospheres, microbial respiration will break down organic material, however, in the South Pacific Gyre the low levels of organic material, the low rates of respiration, and the thin sediments allow the porewater to be oxygenated throughout the entire sediment column. Satellite data images show that some areas in the gyre are greener than the clear blue water. However, the assumption that greener ocean water contains more phytoplankton is not always true. Even though the South Pacific Gyre contains these patches of green water, instead, some studies hypothesize that these green patches are a result of the accumulated waste of marine life. The optical properties of the South Pacific Gyre remain largely unexplored
16.
Northern Hemisphere
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The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined as being in the celestial hemisphere relative to the invariable plane of the solar system as Earths North pole. Due to the Earths axial tilt, winter in the Northern Hemisphere lasts from the December solstice to the March Equinox, the dates vary each year due to the difference between the calendar year and the astronomical year. Its surface is 60. 7% water, compared with 80. 9% water in the case of the Southern Hemisphere, the Arctic is the region north of the Arctic Circle. Its climate is characterized by cold winters and cool summers, precipitation mostly comes in the form of snow. The Arctic experiences some days in summer when the Sun never sets, the duration of these phases varies from one day for locations right on the Arctic Circle to several months near the North Pole, which is the middle of the Northern Hemisphere. Between the Arctic Circle and the Tropic of Cancer lies the Northern Temperate Zone, the changes in these regions between summer and winter are generally mild, rather than extreme hot or cold. However, a temperate climate can have very unpredictable weather, tropical regions are generally hot all year round and tend to experience a rainy season during the summer months, and a dry season during the winter months. In the Northern Hemisphere, objects moving across or above the surface of the Earth tend to turn to the right because of the coriolis effect, as a result, large-scale horizontal flows of air or water tend to form clockwise-turning gyres. These are best seen in circulation patterns in the North Atlantic. For the same reason, flows of air down toward the surface of the Earth tend to spread across the surface in a clockwise pattern. Thus, clockwise air circulation is characteristic of high pressure weather cells in the Northern Hemisphere, conversely, air rising from the northern surface of the Earth tends to draw air toward it in a counterclockwise pattern. Hurricanes and tropical storms spin counter-clockwise in the Northern Hemisphere, the shadow of a sundial moves clockwise in the Northern Hemisphere. When viewed from the Northern Hemisphere, the Moon appears inverted compared to a view from the Southern Hemisphere, the North Pole faces away from the galactic center of the Milky Way. The Northern Hemisphere is home to approximately 6.57 billion people which is around 90% of the total human population of 7.3 billion people
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Southern Hemisphere
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The Southern Hemisphere is the half sphere of Earth which is south of the equator. It contains all or parts of five continents, four oceans and its surface is 80. 9% water, compared with 60. 7% water in the case of the Northern Hemisphere, and it contains 32. 7% of Earths land. Due to the tilt of Earths rotation relative to the Sun, September 22 or 23 is the vernal equinox and March 20 or 21 is the autumnal equinox. The South Pole is in the middle of the southern hemispherical region, Southern Hemisphere climates tend to be slightly milder than those at similar latitudes in the Northern Hemisphere, except in the Antarctic which is colder than the Arctic. This is because the Southern Hemisphere has significantly more ocean and much land, water heats up. In the Southern Hemisphere the sun passes from east to west through the north, sun-cast shadows turn anticlockwise throughout the day and sundials have the hours increasing in the anticlockwise direction. Cyclones and tropical storms spin clockwise in the Southern Hemisphere due to the Coriolis effect, the southern temperate zone, a subsection of the Southern Hemisphere, is nearly all oceanic. Forests in the Southern Hemisphere have special features which set apart from those in the Northern Hemisphere. Both Chile and Australia share, for example, unique species or Nothofagus. The eucalyptus is native to Australia but is now planted in Southern Africa and Latin America for pulp production and, increasingly. Approximately 800,000,000 humans live in the Southern Hemisphere and this is due to the fact that there is significantly less land in the Southern Hemisphere than in the Northern Hemisphere. Africa Antarctica Asia Australia South America Zealandia Media related to Southern Hemisphere at Wikimedia Commons
18.
Boundary current
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Boundary currents are ocean currents with dynamics determined by the presence of a coastline, and fall into two distinct categories, western boundary currents and eastern boundary currents. Eastern boundary currents are relatively shallow, broad and slow-flowing and they are found on the eastern side of oceanic basins. Coastal upwelling often brings nutrient-rich water into eastern boundary current regions, western boundary currents are warm, deep, narrow, and fast flowing currents that form on the west side of ocean basins due to western intensification. They carry warm water from the tropics poleward, examples include the Gulf Stream, the Agulhas Current, and the Kuroshio. Western intensification is the intensification of the arm of an oceanic current. The trade winds blow westward in the tropics, and the westerlies blow eastward at mid-latitudes and this wind pattern applies a stress to the subtropical ocean surface with negative curl in the northern hemisphere and a positive curl in the southern hemisphere. The resulting Sverdrup transport is equatorward in both cases, western intensification also occurs in the polar gyres, where the sign of the wind stress curl and the direction of the resulting currents are reversed. It is because of western intensification that the currents on the boundary of a basin are stronger than those on the eastern boundary. Western intensification was first explained by the American oceanographer Henry Stommel, the wind is blowing towards the west at y =0 and towards the east at y = b. Such currents are observed to be faster, deeper, narrower and warmer than their eastern counterparts. The streamlines exhibit a behavior in all directions, with the height contours demonstrating a nearly parallel relation to the streamlines. The physics of western intensification can be understood through a mechanism that helps maintain the balance along an ocean gyre. He assumed a geostrophic flow, while neglecting any frictional or viscosity effects. Sverdrup introduced a potential vorticity argument to connect the net, interior flow of the oceans to the wind stress. This is accomplished via a decrease in planetary vorticity, a phenomenon attainable through an equator-wardly directed, the opposite is applicable when Ekman divergence is induced, leading to Ekman absorption and a subsequent, water column stretching and poleward return flow, a characteristic of sub-polar gyres. This return flow, as shown by Stommel, occurs in a meridional current, to balance the vorticity source induced by the wind stress forcing, Stommel introduced a linear frictional term in the Sverdrup equation, functioning as the vorticity sink. Walter Munk further implemented Stommels theory of western intensification by using a more realistic frictional term, Ekman Transport Ocean Gyres Sverdrup Balance Thurman, Harold V. Trujillo, Alan P. On the wind-driven ocean circulation, J. Meteorol, Ocean Currents, A Derivative of the Encyclopedia of Ocean Sciences
19.
Gulf Stream
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The process of western intensification causes the Gulf Stream to be a northward accelerating current off the east coast of North America. At about 40°0′N 30°0′W, it splits in two, with the stream, the North Atlantic Drift, crossing to Northern Europe and the southern stream. The Gulf Stream influences the climate of the east coast of North America from Florida to Newfoundland, and it is part of the North Atlantic Gyre. Its presence has led to the development of strong cyclones of all types, the Gulf Stream is also a significant potential source of renewable power generation. The Gulf Stream may be slowing down as a result of climate change, the Gulf Stream is typically 100 kilometres wide and 800 metres to 1,200 metres deep. The current velocity is fastest near the surface, with the maximum speed typically about 2.5 metres per second. European discovery of the Gulf Stream dates to the 1512 expedition of Juan Ponce de León and its existence was also known to Peter Martyr dAnghiera. Benjamin Franklin became interested in the North Atlantic Ocean circulation patterns, Franklin asked Timothy Folger, his cousin twice removed, a Nantucket Island whaling captain, for an answer. Franklin worked with Folger and other experienced ship captains, learning enough to chart the Gulf Stream and he offered this information to Anthony Todd, secretary of the British Post Office, but it was ignored by British sea captains. Franklins Gulf Stream chart was published in 1770 in England, where it was mostly ignored, subsequent versions were printed in France in 1778 and the U. S. in 1786. The Gulf Stream proper is a current, driven largely by wind stress. The North Atlantic Drift, in contrast, is largely thermohaline circulation–driven, in 1958 the oceanographer Henry Stommel noted that very little water from the Gulf of Mexico is actually in the Stream. By carrying warm water northeast across the Atlantic, it makes Western, a river of sea water, called the Atlantic North Equatorial Current, flows westward off the coast of Central Africa. When this current interacts with the northeastern coast of South America, one passes into the Caribbean Sea, while a second, the Antilles Current, flows north and east of the West Indies. These two branches north of the Straits of Florida. The trade winds blow westward in the tropics, and the westerlies blow eastward at mid-latitudes and this wind pattern applies a stress to the subtropical ocean surface with negative curl across the north Atlantic Ocean. The resulting Sverdrup transport is equatorward, the conservation of potential vorticity also causes bends along the Gulf Stream, which occasionally break off due to a shift in the Gulf Streams position, forming separate warm and cold eddies. This overall process, known as western intensification, causes currents on the boundary of an ocean basin, such as the Gulf Stream
20.
Kuroshio Current
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The Kuroshio is a north-flowing ocean current on the west side of the North Pacific Ocean. It is similar to the Gulf Stream in the North Atlantic and is part of the North Pacific ocean gyre, like the Gulf stream, it is a strong western boundary current. It begins off the east coast of Luzon, Philippines, Taiwan and flows northeastward past Japan and it is analogous to the Gulf Stream in the Atlantic Ocean, transporting warm, tropical water northward toward the polar region. It is sometimes known as the Black Stream — the English translation of kuroshio, the path of Kuroshio south of Japan is reported every day. Its counterparts are the North Pacific Current to the north, the California Current to the east, the warm waters of the Kuroshio Current sustain the coral reefs of Japan, the northernmost coral reefs in the world. The branch into the Sea of Japan is called Tsushima Current, western boundary currents transport organisms long distances rapidly and a variety of commercially important marine organisms migrate in these currents in the course of completing their lives. Subtropical gyres occupy a fraction of the worlds ocean and are more productive than originally thought. In addition, their fixation of carbon dioxide is an important factor in the budget for carbon dioxide in the atmosphere. Satellite images of the Kuroshio Current illustrate how the current path meanders, eddies retain their unique form for several months and have their own biological characteristics that depend on where they form. The eddies size and strength decline with distance from major ocean currents, the amount of energy decreases from the rings associated with the major currents and down to eddies remote from those currents. Cyclonic eddies have the potential to cause upwelling that would affect the global primary-production budget, upwelling brings cold, nutrient-rich water to the surface resulting in an increase in productivity. The biological consequences for fish populations that inhabit the shelf are quite large. The Kuroshio is a warm current—24 °C annual average sea-surface temperature—about 100 kilometres wide, the coastal areas are highly productive and the maximum chlorophyll value is found around 100 metres depth. There are indications that eddies contribute to the preservation and survival of fish larvae transported by the Kuroshio, plankton biomass fluctuates yearly and is typically highest in the eddy area of the Kuroshio’s edge. Warm-core rings are not known for having high productivity, however, the biology of the warm-core rings from the Kuroshio Current show results of productivity equally distributed throughout for a couple of reasons. One is upwelling at the periphery, the other is the convective mixing caused by the cooling of water as the ring moves north of the current. The thermostad is the mixed layer that has discrete boundaries. Within this layer, nutrient-rich water is brought to the surface, there are many complex interactions with the warm-core ring and thus lifetime productivity is not very different from the surrounding shelf water
21.
Brazil Current
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The Brazil Current is a warm water current that flows south along the Brazilian south coast to the mouth of the Río de la Plata. This current is caused by diversion of a portion of the Atlantic South Equatorial Current from where that current meets the South American continent and it is a western boundary current like the Gulf Stream, and is indeed its southern counterpart, however, it is considerably shallower and weaker. It flows south from the equator to the west wind drift and it joins the Falkland Current at the Argentine Sea, making it a temperate sea
22.
East Australian Current
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The East Australian Current is the southward western boundary current that is formed from the South Equatorial Current crossing the Coral Sea and reaching the eastern coast of Australia. At around 15° S near the Australian coast the SEC divides forming the flow of the EAC. It is the largest ocean current close to the shores of Australia, the EAC reaches a maximum velocity at 30° S where its flow can reach 90 cm/s. As it flows southward it splits from the coast at around 31° to 32° S, by the time it reaches 33° S it begins to undergo a southward meander while another portion of the transport turns back northward in a tight recirculation. At this location the EAC reaches its maximum transport of nearly 35 Sv, the majority of the EAC flow that does not recirculate will move eastward into the Tasman Front crossing the Tasman Sea just north of the cape of New Zealand. The Tasman Front transport is estimated at 13 Sv, the eastward movement of the EAC through the Tasman Front and reattaching to the coastline of New Zealand forms the East Auckland Current. The EAC also acts to transport tropical marine fauna to habitats in sub-tropical regions along the south east Australian coast, in the 2003 Disney/Pixar animated film Finding Nemo, the EAC is portrayed as a superhighway that fish and sea turtles use to travel down the east coast of Australia. The characters Marlin and Dory join a group of sea turtles in using the EAC to help them travel to Sydney Harbour, the basic premise of this storyline is correct. Every summer, thousands of fish are swept from the Great Barrier Reef to Sydney Harbour, ocean current Oceanic gyres Physical oceanography Image of the East Australian Current. Sea surface temperature and currents, New South Wales
23.
Agulhas Current
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The Agulhas Current /əˈɡʌləs/ is the western boundary current of the southwest Indian Ocean. It flows down the east coast of Africa from 27°S to 40°S and it is narrow, swift and strong. The sources of the Agulhas Current are the East Madagascar Current, the Mozambique Current, the net transport of the Agulhas Current is estimated as 100 Sv. The flow of the Agulhas Current is directed by the topography, the current follows the continental shelf from Maputo to the tip of the Agulhas Bank. Here the momentum of the current overcomes the vorticity balance holding the current to the topography, the current reaches its maximum transport near the Agulhas Bank where it ranges between 95-136 Sv. The core of the current is defined as where the surface velocities reaches 100 cm/s, the mean peak speed is 136 cm/s, but the current can reach 245 cm/s. As the Agulhas Current flows south along the African east coast, it tends to bulge inshore frequently and these bulges are occasionally followed by a much larger offshore bulge, known as Natal pulses. Natal pulses move along the coast at 20 km per day, an ACM can bulge up to 20 km and a NP up to 120 km from the currents mean position. The AC passes 34 km offshore and an ACM can reach 123 km offshore, when the AC meanders, its width broadens from 88 km to 125 km and its velocity weakens from 208 cm/s to 136 cm/s. An ACM induces a strong inshore counter-current, large-scale cyclonic meanders known as Natal pulses are formed as the Agulhas Current reaches the continental shelf on the South African east-coast. As these pulses moves along the coast on the Agulhas Bank, such a ring shedding can be triggered by a Natal pulse alone, but sometimes meanders on the Agulhas Return Current merge to contribute to the shedding of an Agulhas ring. This water becomes the Agulhas Return Current, rejoining the Indian Ocean Gyre and it is estimated that up to 85 Sv of the net transport is returned to the Indian Ocean through the retroflection. The remaining water is transported into the South Atlantic Gyre in the Agulhas Leakage, along with direct branch currents, this leakage takes place in surface water filaments, and Agulhas Eddies. It is estimated that as much as 15 Sv of Indian Ocean water is leaked directly into the South Atlantic,10 Sv of this is relatively warm, salty thermocline water, with the remaining 5 Sv being cold, low salinity Antarctic Intermediate Water. Since Indian Ocean water is warmer and saltier than South Atlantic water. This heat flux is believed to contribute to the rate of evaporation in the South Atlantic. It should be noted that an amount of the Agulhas Leakage joins the North Brazil Current. Surface water filaments are estimated to account for up to 13% of the total salt transport from the Agulhas Current into the Benguela Current, due to surface dissipation, these filaments are not believed to significantly contribute to inter-basin heat flux
24.
Low-pressure area
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A low-pressure area, low, or depression is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure systems form under areas of wind divergence that occur in the levels of the troposphere. The formation process of an area is known as cyclogenesis. Within the field of meteorology, atmospheric divergence aloft occurs in two areas, the first area is on the east side of upper troughs, which form half of a Rossby wave within the Westerlies. A second area of wind divergence aloft occurs ahead of embedded shortwave troughs, diverging winds aloft ahead of these troughs cause atmospheric lift within the troposphere below, which lowers surface pressures as upward motion partially counteracts the force of gravity. Thermal lows form due to localized heating caused by greater sunshine over deserts, since localized areas of warm air are less dense than their surroundings, this warmer air rises, which lowers atmospheric pressure near that portion of the Earths surface. Large-scale thermal lows over continents help drive monsoon circulations, low-pressure areas can also form due to organized thunderstorm activity over warm water. When this occurs over the tropics in concert with the Intertropical Convergence Zone, Monsoon troughs reach their northerly extent in August and their southerly extent in February. When a convective low acquires a well-hot circulation in the tropics it is termed a tropical cyclone, Tropical cyclones can form during any month of the year globally, but can occur in either the northern or southern hemisphere during November. Since clouds reflect sunlight, incoming solar radiation decreases, which causes lower temperatures during the day. At night the effect of clouds on outgoing longwave radiation, such as heat energy from the surface. The stronger the area of low pressure, the stronger the winds experienced in its vicinity, globally, low-pressure systems are most frequently located over the Tibetan Plateau and in the lee of the Rocky mountains. In Europe, recurring low-pressure weather systems are known as depressions. Cyclogenesis is the development and strengthening of cyclonic circulations, or low-pressure areas, cyclogenesis is the opposite of cyclolysis, and has an anticyclonic equivalent which deals with the formation of high-pressure areas—anticyclogenesis. Cyclogenesis is a term for several different processes, all of which result in the development of some sort of cyclone. Meteorologists use the term cyclone where circular pressure systems flow in the direction of the Earths rotation, the largest low-pressure systems are cold-core polar cyclones and extratropical cyclones which lie on the synoptic scale. Warm-core cyclones such as cyclones, mesocyclones, and polar lows lie within the smaller mesoscale. Subtropical cyclones are of intermediate size, cyclogenesis can occur at various scales, from the microscale to the synoptic scale
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Aleutian Low
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The Aleutian Low is a semi-permanent low pressure center located near the Aleutian Islands during the winter. It is one of the centers of action in the atmospheric circulation of the Northern Hemisphere. However, the presence of the continents disrupts this motion, and the belt of low pressure is well developed only in the North Pacific. The Aleutian Low is characterized by many strong cyclones, cyclones which form in the subpolar latitudes in the North Pacific typically slow down and reach maximum intensity in the area of the Aleutian Low. In summer, remnants of typhoons can go past the Aleutian low, national council for Science and the Environment
26.
Ekman transport
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Ekman transport, part of Ekman motion theory first investigated in 1902 by Vagn Walfrid Ekman, is the term given for the 90° net transport of the surface layer of a fluid by wind forcing. This phenomenon was first noted by Fridtjof Nansen, who recorded that ice transport appeared to occur at an angle to the wind direction during his Arctic expedition during the 1890s. Ekman theory explains the state of circulation if water currents were driven only by the transfer of momentum from the wind. In the physical world, this is difficult to observe because of the influences of many simultaneous current driving forces, though the following theory technically applies to the idealized situation involving only wind forces, Ekman motion describes the wind-driven portion of circulation seen in the surface layer. Surface currents flow at a 45° angle to the due to a balance between the Coriolis force and the drags generated by the wind and the water. If the ocean is divided vertically into thin layers, the magnitude of the velocity decreases from a maximum at the surface until it dissipates, the direction also shifts slightly across each subsequent layer. This is called the Ekman spiral, the layer of water from the surface to the point of dissipation of this spiral is known as the Ekman layer. If all flow over the Ekman layer is integrated, the net transportation is at 90° to the right of the wind in the northern hemisphere. Some assumptions of the dynamics involved in the process must be made in order to simplify the process to a point where it is solvable. Here M x and M y represent the zonal and meridional mass transport terms with units of mass per time per unit length. Contrarily to common logic, north-south winds cause mass transport in the East-West direction, in order to understand the vertical velocity structure of the water column, equations 1 and 2 can be rewritten in terms of the vertical eddy viscosity term. ∂ τ x ∂ z = ρ A z ∂2 u ∂ z 2, ∂ τ y ∂ z = ρ A z ∂2 v ∂ z 2, where A z is the vertical eddy viscosity coefficient. This gives a set of equations of the form A z ∂2 u ∂ z 2 = − f v, A z ∂2 v ∂ z 2 = f u. In order to solve this system of two equations, two boundary conditions can be applied, →0 as z → ∞, friction is equal to wind stress at the free surface. Things can be simplified by considering wind blowing in the y-direction only. By solving this at z=0, the current is found to be 45 degrees to the right of the wind in the Northern Hemisphere. This also gives the shape of the Ekman spiral, both in magnitude and direction. Integrating these equations over the Ekman layer shows that the net Ekman transport term is 90 degrees to the right of the wind in the Northern Hemisphere
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Upwelling
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The nutrient-rich upwelled water stimulates the growth and reproduction of primary producers such as phytoplankton. Due to the biomass of phytoplankton and presence of water in these regions, upwelling zones can be identified by cool sea surface temperatures. The increased availability in upwelling regions results in levels of primary productivity. Approximately 25% of the global marine fish catches come from five upwellings that occupy only 5% of the total ocean area. Upwellings that are driven by coastal currents or diverging open ocean have the greatest impact on nutrient-enriched waters, the three main drivers that work together to cause upwelling are wind, Coriolis effects, and Ekman transport. They operate differently for different types of upwelling, but the effects are the same. In the overall process of upwelling, winds blow across the sea surface at a particular direction, as a result of the wind, the water is transported a net of 90 degrees from the direction of the wind due to Coriolis forces and Ekman transport. This results in a spiral of water movement down the water column, then, it is the Coriolis forces that dictate which way the water will move, in the Northern hemisphere, the water is transported to the right of the direction of the wind. In the Southern Hemisphere, the water is transported to the left of the wind, if this net movement of water is divergent, then upwelling of deep water occurs to replace the water that was lost. The major upwellings in the ocean are associated with the divergence of currents that bring deeper, colder, coastal upwelling is the best known type of upwelling, and the most closely related to human activities as it supports some of the most productive fisheries in the world. Wind-driven currents are diverted to the right of the winds in the Northern Hemisphere, the result is a net movement of surface water at right angles to the direction of the wind, known as the Ekman transport. When Ekman transport is occurring away from the coast, surface waters moving away are replaced by deeper, colder, and denser water. Normally, this process occurs at a rate of about 5–10 meters per day. Deep waters are rich in nutrients, including nitrate, phosphate and silicic acid, Upwelling regions therefore result in very high levels of primary production in comparison to other areas of the ocean. They account for about 50% of global marine productivity, high primary production propagates up the food chain because phytoplankton are at the base of the oceanic food chain. All of these currents support major fisheries, the four major eastern boundary currents in which coastal upwelling primarily occurs are the Canary Current, Benguela Current, California Current, and Humboldt Current. The Benguela Current is the boundary of the South Atlantic subtropical gyre. The subsystems are divided by an area of permanent upwelling off of Luderitz, the California Current System is an eastern boundary current of the North Pacific that is also characterized by a north and south split
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Antarctic Circumpolar Current
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The Antarctic Circumpolar Current is an ocean current that flows clockwise from west to east around Antarctica. An alternative name for the ACC is the West Wind Drift, the ACC is the dominant circulation feature of the Southern Ocean and has a mean transport of 100-150 Sverdrups, making it the largest ocean current. More recent research puts this number at over 173 Sv. The current is due to the lack of any landmass connecting with Antarctica. Associated with the Circumpolar Current is the Antarctic Convergence, where the cold Antarctic waters meet the waters of the subantarctic. These nurture high levels of phytoplankton with associated copepods and krill, and resultant foodchains supporting fish, whales, seals, penguins, albatrosses and a wealth of other species. The clipper route, which is the fastest sailing route around the world, the current creates the Ross and Weddell gyres. The ACC connects the Atlantic, Pacific and Indian Oceans, the current is strongly constrained by landform and bathymetric features. Passing through the Indian Ocean, the current first retroflects the Agulhas Current to form the Agulhas Return Current before it is split by the Kerguelen Plateau, deflection is also seen as it passes over the mid-ocean ridge in the Southeast Pacific. The current is accompanied by three fronts, the Subantarctic front, the Polar front, and the Southern ACC front, furthermore, the waters of the Southern Ocean are separated from the warmer and saltier subtropical waters by the subtropical front. The northern boundary of the ACC is defined by the edge of the SAF. Still further south lies the PF, which is marked by a transition to cold, relatively fresh. Here a temperature minimum is allowed by salinity dominating density stratification, further south still is the SACC, which is determined as the southernmost extent of Circumpolar Deep Water. This water mass flows along the shelfbreak of the western Antarctic Peninsula and thus marks the most southerly water flowing through Drake Passage, the bulk of the transport is carried in the middle two fronts. The total transport of the ACC at Drake Passage is estimated to be around 135 Sv, or about 135 times the transport of all the worlds rivers combined. There is a small addition of flow in the Indian Ocean, with the transport south of Tasmania reaching around 147 Sv. The circumpolar current is driven by the westerly winds in the latitudes of the Southern Ocean. In latitudes where there are continents, winds blowing on light surface water can pile up light water against these continents
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Southern Ocean
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As such, it is regarded as the fourth-largest of the five principal oceanic divisions, smaller than the Pacific, Atlantic, and Indian Oceans but larger than the Arctic Ocean. This ocean zone is cold, northward flowing waters from the Antarctic mix with warmer subantarctic waters. By way of his voyages in the 1770s, Captain James Cook proved that waters encompassed the southern latitudes of the globe. Since then, geographers have disagreed on the Southern Oceans northern boundary or even existence, considering the part of the Pacific, Atlantic. Others regard the seasonally-fluctuating Antarctic Convergence as the natural boundary, Borders and names for oceans and seas were internationally agreed when the International Hydrographic Bureau, the precusor to the IHO, convened the First International Conference on 24 July 1919. The IHO then published these in its Limits of Oceans and Seas, Australian authorities regard the Southern Ocean as lying immediately south of Australia. Map publishers using the term Southern Ocean on their maps include Hema Maps, Southern Ocean is an obsolete name for the Pacific Ocean or South Pacific, coined by Vasco Núñez de Balboa, the first European to discover it, who approached it from the north. The South Seas is an archaic synonym. A1745 British Act of Parliament established a prize for discovering a Northwest Passage to the Western and Southern Ocean of America, authors using Southern Ocean to name the waters encircling the unknown southern polar regions used varying limits. James Cooks account of his second voyage implies New Caledonia borders it, peacocks 1795 Geographical Dictionary said it lay to the southward of America and Africa, John Payne in 1796 used 40 degrees as the northern limit, the 1827 Edinburgh Gazetteer used 50 degrees. The United Kingdoms South Australia Act 1834 described the waters forming the southern limit of the new colony of South Australia as the Southern Ocean. The Colony of Victorias Legislative Council Act of 1881 delimited part of the division of Bairnsdale as along the New South Wales boundary to the Southern ocean. The limit then followed the west coast of Tasmania southwards to the South East Cape and then went eastwards to Broughton Island, New Zealand, the northern limits of the Southern Ocean were moved southwards in the IHOs 1937 second edition of the Limits of Oceans and Seas. From this edition, much of the northern limit ceased to abut land masses. As is discussed in detail below, prior to the 2002 edition the limits of oceans explicitly excluded the seas lying within each of them. The Great Australian Bight was unnamed in the 1928 edition, and it therefore encompassed former Southern Ocean waters but was technically not inside any of the three adjacent oceans by 1937. To perform direct comparisons of current and former limits of oceans it is necessary to consider, or at least be aware of, the limits of the Atlantic, Pacific and Indian Oceans have therefore been extended South to the Antarctic Continent. The IHO readdressed the question of the Southern Ocean in a survey in 2000, of its 68 member nations,28 responded, and all responding members except Argentina agreed to redefine the ocean, reflecting the importance placed by oceanographers on ocean currents
30.
Weddell Sea
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The Weddell Sea is part of the Southern Ocean and contains the Weddell Gyre. Its land boundaries are defined by the bay formed from the coasts of Coats Land, the easternmost point is Cape Norvegia at Princess Martha Coast, Queen Maud Land. To the east of Cape Norvegia is the King Haakon VII Sea, much of the southern part of the sea is covered by a permanent, massive ice shelf field, the Filchner-Ronne Ice Shelf. The sea is contained within the two overlapping Antarctic territorial claims of Argentina, and Britain, and also partially within the territorial claim of Chile. At its widest the sea is around 2,000 kilometres across, various ice shelves, including the Filchner-Ronne Ice Shelf, fringe the Weddell sea. Whilst a dramatic event, the area that disappeared was far smaller than the area of ice shelf that remains. The Weddell Sea has been deemed by scientists to have the clearest water of any sea, the Ross Sea is relatively peaceful, predictable, and safe. The sea is named after the Scottish sailor James Weddell, who entered the sea in 1823 and originally named it after King George IV, also in 1823, the American sealing captain Benjamin Morrell claimed to have seen land some 10–12° east of the seas actual eastern boundary. He called this New South Greenland, but its existence was disproved when the sea was more fully explored in the early 20th century. Weddell got as far south as 74°S, the furthest southern penetration since Weddell, the Weddell Sea is an important area of deep water mass formation through cabbeling, the main driving force of the thermohaline circulation. Deep water masses are formed through cabbeling in the North Atlantic and are caused by differences in temperature. In the Weddell sea this is brought mainly by brine exclusion. In 1823, British sailor James Weddell discovered the Weddell Sea, Otto Nordenskiöld, leader of the 1901-1904 Swedish Antarctic Expedition, spent a winter at Snow Hill with a team of four men when the relief ship became beset in ice and was finally crushed. The crew managed to reach Paulet Island where they wintered in a primitive hut, Nordenskiöld and the others finally were picked up by the Argentine Navy at Hope Bay. The Antarctic Sound is named after the ship of Otto Nordenskiöld. The sound that separates the tip of the Antarctic Peninsula from Dundee Island is also named “Iceberg Alley”, Snowhill Island, located east of the Antarctic Peninsula. It is almost completely snow-capped, hence its name, Swedish Antarctic Expedition under Otto Nordenskiöld built a cabin on the island in 1902 where Nordenskiöld and three members of the expedition had to spend two winters. In 1915, Ernest Shackleton’s ship, the Endurance got trapped and was crushed by ice in this sea, after 15 months on the pack-ice Shackleton and his men managed to reach Elephant Island and finally safely returned
31.
Ross Sea
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The Ross Sea is a deep bay of the Southern Ocean in Antarctica, between Victoria Land and Marie Byrd Land. It derives its name from the British explorer James Ross who visited this area in 1841. To the west of the sea lies Ross Island and to the east Roosevelt Island, while the southernmost part is covered by the Ross Ice Shelf, the underlying rocks are of upper Precambrian to lower Paleozoic age and are partly composed of calcium carbonate. The circulation of the Ross Sea is dominated by an ocean gyre. The circumpolar deep water current is a warm, salty. The Ross Sea is covered with ice for most of the year, the nutrient-laden water supports an abundance of plankton and this encourages a rich marine fauna. At least ten species, six bird species and 95 fish species are found here, as well as many invertebrates. New Zealand has claimed that the sea comes under their jurisdiction as part of the Ross Dependency, Marine biologists consider the sea to have a high level of biological diversity and it is the site of much scientific research. It is also the focus of some environmentalist groups who have campaigned to have the area proclaimed as a marine reserve. The Ross Sea was discovered by James Ross in 1841, in the west of the Ross Sea is Ross Island with the Mt. Erebus volcano, in the east Roosevelt Island. The southern part is covered by the Ross Ice Shelf, roald Amundsen started his South Pole expedition in 1911 from the Bay of Whales, which was located at the shelf. In the west of the Ross sea, McMurdo Sound is a port which is free of ice during the summer. The southernmost part of the Ross Sea is Gould Coast, which is two hundred miles from the Geographic South Pole. All land masses in the Ross Sea are claimed by New Zealand to fall under the jurisdiction of the Ross Dependency, a 10-metre long colossal squid weighing 495 kilograms was captured in the Ross Sea on February 22,2007. Ross System rocks are of upper Precambrian to lower Paleozoic age and these miogeosyncline metasedimentary rocks are usually folded about northwest and southeast axes and are partly composed of calcium carbonate, often including limestone. Groups within the Ross System include the Robertson Bay Group, Priestley Group, Skelton Group, Beardmore Group, Byrd Group, Queen Maud Group, the Robertson Bay Group ranges from 56 to 76% silica and compares closely with other Ross System members. The Priestley Group rocks are similar to those of the Robertson Bay Group and include dark slates, argillites, siltstones and they can be found near the Priestley and Campbell glaciers. For thirty miles along the lower Skelton Glacier are the calcareous greywackes and argillites of the Skelton Group, the region between the lower Beardmore Glacier and the lower Shackelton Glacier sits the Beardmore Group
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Ross Gyre
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The Ross Gyre is one of the two gyres that exist within the Southern Ocean. The gyre is located in the Ross Sea, and rotates clockwise, the gyre is formed by interactions between the Antarctic Circumpolar Current and the Antarctic Continental Shelf. Sea ice has been noted to persist in the area of the gyre. There is some evidence that global warming has resulted in decrease of the salinity of the waters of the Ross Gyre since the 1950s. Oceanic current Physical oceanography Weddell Gyre
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Subtropical ridge
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It is the product of the global air circulation cell known as the Hadley Cell. The air descending from the upper troposphere flows out from its center at surface level toward the upper and lower latitudes of each hemisphere, the subtropical ridge moves poleward during the summer, reaching its most northern latitude in early fall, before moving equatorward during the cold season. The change of the position during ENSO cycles changes the tracks of tropical cyclones that form around their equatorward. As the subtropical ridge varies in position and strength, it can enhance or depress monsoon regimes around their low-latitude periphery, the term horse latitudes refers to and is synonymous with the subtropical ridge or subtropical high. Heating of the earth near the equator leads to large amounts of convection along the trough or Intertropical convergence zone. This air mass rise to the stratosphere where it diverges. As it moves towards the mid-latitudes on both sides of the equator, the air cools and sinks, the resulting air mass subsidence creates a subtropical ridge of high pressure near the 30th parallel in both hemispheres. At the surface level, the sinking air diverges again with some returning to the equator and this circulation on each side of the equator is known as the Hadley cell and leads to the formation of the subtropical ridge. Many of the deserts are caused by these climatological high-pressure areas. The subtropical ridge starts migrating poleward in late spring reaching its zenith in early autumn before retreating equatorward during the fall, winter. The equatorward migration of the ridge during the cold season is due to increasing north-south temperature differences between the poles and tropics. The latitudinal movement of the ridge is strongly correlated with the progression of the monsoon trough or Intertropical Convergence Zone. Most tropical cyclones form on the side of the subtropical ridge closer to the equator, when the subtropical ridge shifts due to ENSO, so will the preferred tropical cyclone tracks. When the Atlantic Multidecadal Oscillations mode is favorable to tropical development, it amplifies the subtropical ridge across the central. When the subtropical ridge in the northwest Pacific is stronger than normal, the subtropical ridge position is linked to how far northward monsoon moisture and thunderstorms extend into the United States. The subtropical ridge across North America typically migrates far enough northward to begin monsoon conditions across the Desert Southwest from July to September, when the subtropical ridge is farther north than normal towards the Four Corners, monsoon thunderstorms can spread northward into Arizona. When the high pressure moves south, its circulation cuts off the moisture, when surface winds become light, the subsidence produced directly under the subtropical ridge can lead to a buildup of particulates in urban areas under the ridge, leading to widespread haze. If the low relative humidity rises towards 100 percent overnight
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Pacific Ocean
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The Pacific Ocean is the largest and deepest of the Earths oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean in the south and is bounded by Asia and Australia in the west, the Mariana Trench in the western North Pacific is the deepest point in the world, reaching a depth of 10,911 metres. Both the center of the Water Hemisphere and the Western Hemisphere are in the Pacific Ocean, the oceans current name was coined by Portuguese explorer Ferdinand Magellan during the Spanish circumnavigation of the world in 1521, as he encountered favourable winds on reaching the ocean. He called it Mar Pacífico, which in both Portuguese and Spanish means peaceful sea, important human migrations occurred in the Pacific in prehistoric times. Long-distance trade developed all along the coast from Mozambique to Japan, trade, and therefore knowledge, extended to the Indonesian islands but apparently not Australia. By at least 878 when there was a significant Islamic settlement in Canton much of trade was controlled by Arabs or Muslims. In 219 BC Xu Fu sailed out into the Pacific searching for the elixir of immortality, from 1404 to 1433 Zheng He led expeditions into the Indian Ocean. The east side of the ocean was discovered by Spanish explorer Vasco Núñez de Balboa in 1513 after his expedition crossed the Isthmus of Panama and he named it Mar del Sur because the ocean was to the south of the coast of the isthmus where he first observed the Pacific. Later, Portuguese explorer Ferdinand Magellan sailed the Pacific East to West on a Castilian expedition of world circumnavigation starting in 1519, Magellan called the ocean Pacífico because, after sailing through the stormy seas off Cape Horn, the expedition found calm waters. The ocean was often called the Sea of Magellan in his honor until the eighteenth century, sailing around and east of the Moluccas, between 1525 and 1527, Portuguese expeditions discovered the Caroline Islands, the Aru Islands, and Papua New Guinea. In 1542–43 the Portuguese also reached Japan, in 1564, five Spanish ships consisting of 379 explorers crossed the ocean from Mexico led by Miguel López de Legazpi and sailed to the Philippines and Mariana Islands. The Manila galleons operated for two and a half centuries linking Manila and Acapulco, in one of the longest trade routes in history, Spanish expeditions also discovered Tuvalu, the Marquesas, the Cook Islands, the Solomon Islands, and the Admiralty Islands in the South Pacific. In the 16th and 17th century Spain considered the Pacific Ocean a Mare clausum—a sea closed to other naval powers, as the only known entrance from the Atlantic the Strait of Magellan was at times patrolled by fleets sent to prevent entrance of non-Spanish ships. On the western end of the Pacific Ocean the Dutch threatened the Spanish Philippines, Spain also sent expeditions to the Pacific Northwest reaching Vancouver Island in southern Canada, and Alaska. The French explored and settled Polynesia, and the British made three voyages with James Cook to the South Pacific and Australia, Hawaii, and the North American Pacific Northwest, one of the earliest voyages of scientific exploration was organized by Spain in the Malaspina Expedition of 1789–1794. It sailed vast areas of the Pacific, from Cape Horn to Alaska, Guam and the Philippines, New Zealand, Australia, and the South Pacific. Growing imperialism during the 19th century resulted in the occupation of much of Oceania by other European powers, and later, Japan, in Oceania, France got a leading position as imperial power after making Tahiti and New Caledonia protectorates in 1842 and 1853 respectively. After navy visits to Easter Island in 1875 and 1887, Chilean navy officer Policarpo Toro managed to negotiate an incorporation of the island into Chile with native Rapanui in 1888, by occupying Easter Island, Chile joined the imperial nations
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Ocean heat content
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Oceanic heat content is the heat stored in the ocean. Oceanography and climatology are the branches which study ocean heat content. Changes in the heat content play an important role in the sea level rise, because of thermal expansion. It is with high confidence that ocean warming accounts for 90% of the energy accumulation from global warming between 1971 and 2010, in SI units, H has units of J·m−2. Multiplying this quantity by the area of a basin, or entire ocean, gives the total heat content. Ocean heat content can be computed using temperature measurements obtained by a Nansen bottle, the World Ocean Database Project is the largest database for temperature profiles from all of the world’s oceans. Several studies in recent years have found a multi-decadal oscillation increase in OHC of the deep and upper ocean regions, studies based on ARGO indicate that ocean surface winds, especially the subtropical trade winds in the Pacific Ocean, change ocean heat vertical distribution. This results in changes among ocean currents, and an increase of the subtropical overturning, depending on stochastic natural variability fluctuations, during La Niña years around 30% more heat from the upper ocean layer is transported into the deeper ocean. Model studies indicate that ocean currents transport more heat into deeper layers during La Niña years, years with increased ocean heat uptake have been associated with negative phases of the interdecadal Pacific oscillation. This is of particular interest to scientists who use the data to estimate the ocean heat uptake. A study in 2015 concluded that ocean heat content increases by the Pacific Ocean, were compensated by a distribution of OHC into the Indian Ocean
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Thermohaline circulation
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Thermohaline circulation is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, wind-driven surface currents travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes. This dense water then flows into the ocean basins, while the bulk of it upwells in the Southern Ocean, the oldest waters upwell in the North Pacific. Extensive mixing therefore takes place between the basins, reducing differences between them and making the Earths oceans a global system. On their journey, the water masses transport both energy and matter around the globe, as such, the state of the circulation has a large impact on the climate of the Earth. The thermohaline circulation is called the ocean conveyor belt, the great ocean conveyor, or the global conveyor belt. On occasion, it is used to refer to the overturning circulation. Moreover, temperature and salinity gradients can lead to circulation effects that are not included in the MOC itself. The movement of surface currents pushed by the wind is fairly intuitive, for example, the wind easily produces ripples on the surface of a pond. Thus the deep ocean—devoid of wind—was assumed to be perfectly static by early oceanographers, however, modern instrumentation shows that current velocities in deep water masses can be significant. In general ocean water velocities range from fractions of centimeters per second to more than 1 m/s in surface currents like the Gulf Stream. In the deep ocean, the predominant driving force is differences in density, caused by salinity, there is often confusion over the components of the circulation that are wind and density driven. Note that ocean currents due to tides are also significant in places, most prominent in relatively shallow coastal areas. There they are thought to facilitate mixing processes, especially diapycnal mixing. The density of water is not globally homogeneous, but varies significantly and discretely. Sharply defined boundaries exist between water masses which form at the surface, and subsequently maintain their own identity within the ocean, but these sharp boundaries are not to be imagined spatially but rather in a T-S-diagram where water masses are distinguished. They position themselves above or below each other according to their density, warm seawater expands and is thus less dense than cooler seawater. Saltier water is denser than water because the dissolved salts fill interstices between water molecules, resulting in more mass per unit volume
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Human impact on the environment
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Human impact on the environment or anthropogenic impact on the environment includes impacts on biophysical environments, biodiversity, and other resources. The term anthropogenic designates an effect or object resulting from human activity, the atmospheric scientist Paul Crutzen introduced the term Anthropocene in the mid-1970s. The term is used in the context of pollution emissions that are produced as a result of human activities but applies broadly to all major human impacts on the environment. Environmental impacts caused by the application of technology are often perceived as unavoidable for several reasons, third, according to the second law of thermodynamics, order can be increased within a system only by increasing disorder or entropy outside the system. Thus, technologies can create “order” in the economy only at the expense of increasing “disorder” in the environment. According to a number of studies, increased entropy is likely to be correlated to environmental impacts. The environmental impact of agriculture based on the wide variety of agricultural practices employed around the world. Ultimately, the impact depends on the production practices of the system used by farmers. The connection between emissions into the environment and the system is indirect, as it also depends on other climate variables such as rainfall. An example of a means-based indicator would be the quality of groundwater, an indicator reflecting the loss of nitrate to groundwater would be effect-based. The environmental impact of agriculture involves a variety of factors from the soil, to water, the air, animal and soil diversity, plants, and the food itself. Some of the issues that are related to agriculture are climate change, deforestation, genetic engineering, irrigation problems, pollutants, soil degradation. These conservation issues are part of conservation, and are addressed in fisheries science programs. There is a gap between how many fish are available to be caught and humanity’s desire to catch them, a problem that gets worse as the world population grows. The journal Science published a study in November 2006, which predicted that, at prevailing trends. Many countries, such as Tonga, the United States, Australia and New Zealand, the impacts stem from the changed hydrological conditions owing to the installation and operation of the scheme. An irrigation scheme draws water from the river and distributes it over the irrigated area. These may be called direct effects, effects on soil and water quality are indirect and complex, and subsequent impacts on natural, ecological and socio-economic conditions are intricate
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Great Pacific garbage patch
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The Great Pacific garbage patch, also described as the Pacific trash vortex, is a gyre of marine debris particles in the central North Pacific Ocean discovered between 1985 and 1988. It is located roughly between 135°W to 155°W and 35°N and 42°N, the patch extends over an indeterminate area of widely varying range depending on the degree of plastic concentration used to define the affected area. The patch is characterized by high relative concentrations of pelagic plastics, chemical sludge. Its low density prevents detection by satellite photography, or even by casual boaters or divers in the area and it consists primarily of a small increase in suspended, often microscopic, particles in the upper water column. The great Pacific garbage patch was described in a 1988 paper published by the National Oceanic and Atmospheric Administration of the United States, the description was based on results obtained by several Alaska-based researchers between 1985 and 1988 that measured neustonic plastic in the North Pacific Ocean. Researchers found high concentrations of marine debris accumulating in regions governed by ocean currents and they specifically indicated the North Pacific Gyre. Charles J. Moore, returning home through the North Pacific Gyre after competing in the Transpac sailing race in 1999, Moore alerted the oceanographer Curtis Ebbesmeyer, who subsequently dubbed the region the Eastern Garbage Patch. The area is featured in media reports as an exceptional example of marine pollution. The patch is not easily visible, because it consists of tiny pieces almost invisible to the naked eye, a similar patch of floating plastic debris is found in the Atlantic Ocean, called the North Atlantic garbage patch. The garbage patch occupies a large and relatively stationary region of the North Pacific Ocean bound by the North Pacific Gyre, the gyres rotational pattern draws in waste material from across the North Pacific Ocean, including coastal waters off North America and Japan. As material is captured in the currents, wind-driven surface currents gradually move floating debris toward the center, there is no strong scientific data concerning the origins of pelagic plastics. The figure that an estimated 80% of the garbage comes from land-based sources, according to a 2011 EPA report, The primary source of marine debris is the improper waste disposal or management of trash and manufacturing products, including plastics. Debris is generated on land at marinas, ports, rivers, harbors, docks, debris is generated at sea from fishing vessels, stationary platforms and cargo ships. Pollutants range in size from abandoned fishing nets to micro-pellets used in abrasive cleaners, currents carry debris from the west coast of North America to the gyre in about six years, and debris from the east coast of Asia in a year or less. The size of the patch is unknown, because large items readily visible from a deck are uncommon. Most debris consists of plastic particles suspended at or just below the surface. Instead, the size of the patch is determined by sampling, estimates of size range from 700,000 square kilometres to more than 15,000,000 square kilometres, or, in some media reports, up to twice the size of the continental United States. Such estimates, however, are given the complexities of sampling
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Indian Ocean garbage patch
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The patch does not appear as a continuous debris field. As with other patches in each of the five oceanic gyres, the plastics in it break down to ever smaller particles, and to constituent polymers. As with the patches, the field constitutes an elevated level of pelagic plastics, chemical sludge. The North Atlantic garbage patch was discovered in 2010, the existence of the Great Pacific garbage patch, the first to be discovered, was predicted in a 1988 paper published by the National Oceanic and Atmospheric Administration of the United States. The prediction was based on results obtained by several Alaska-based researchers between 1985 and 1988 that measured neustonic plastic in the North Pacific Ocean. Research studying trash washed onto beaches in and around the Indian Ocean suggested that there would be found in the water column in the Indian Ocean as well. On the Indian Ocean leg of their trip, they travelled between Perth, Australia, and Port Louis, Mauritius, each of the samples they collected in the 4,800 km between contained plastic. They found that the South Atlantic, South Pacific, and Indian Ocean gyres were affected in the way as the North Pacific. Anna Cummins, cofounder of 5 Gyres Institute called the pollution they found a thin plastic soup, Great Pacific garbage patch North Atlantic garbage patch Plastisphere Notes Further reading Gregory, M. R. Ryan, P. G. Pelagic plastics and other seaborne persistent synthetic debris, a review of Southern Hemisphere perspectives, in Coe, J. M. & Rogers, D. B. eds. CS1 maint, Uses editors parameter Masahisa Kubota, Katsumi Takayama, movement and accumulation of floating marine debris simulated by surface currents derived from satellite data. School of Marine Science and Technology, Tokai University, retrieved 28 July 2010. com Sea of Trash – New York Times Magazine Captain Charles Moore on the seas of plastic Charles Moore, Sailing the Great Pacific Garbage Patch – TED Conference talk
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North Atlantic garbage patch
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The North Atlantic garbage patch is an area of man-made marine debris found floating within the North Atlantic Gyre, originally documented in 1972. The patch is estimated to be hundreds of kilometres across in size, the debris zone shifts by as much as 1,600 km north and south seasonally, and drifts even farther south during the El Niño-Southern Oscillation, according to the NOAA. To study the scale of the debris accumulation in the area. Nearly 7,000 students from the SEA semester program have been dragging 6,100 fine-mesh nets through the Atlantic over 22 years. The gyre in the North Atlantic Ocean contains plastic marine pollution in a pattern, while eating their normal source of food, plastic ingestion can be unavoidable to wildlife. On 11 April 2013 in order to create awareness, artist Maria Cristina Finucci founded The Garbage patch state at UNESCO –Paris in front of Director General Irina Bokova, first of a series of events under the patronage of UNESCO and of Italian Ministry of the Environment
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Anticyclone
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Effects of surface-based anticyclones include clearing skies as well as cooler, drier air. Fog can also form overnight within a region of higher pressure, sir Francis Galton first discovered anticyclones in the 1860s. Preferred areas within a flow pattern in higher levels of the hydrosphere are beneath the western side of troughs. High-pressure systems are referred to as anticyclones. Their circulation is sometimes referred to as cum sole, subtropical high pressure zones form along the descending portion of the Hadley cell circulation. Upper-level high-pressure areas lie over tropical cyclones due to their warm core nature, surface anticyclones form due to downward motion through the troposphere, the atmospheric layer where weather occurs. Preferred areas within a flow pattern in higher levels of the troposphere are beneath the western side of troughs. Because they weaken with height, these systems are cold. Heating of the earth near the equator forces upward motion and convection along the trough or intertropical convergence zone. The divergence over the near-equatorial trough leads to air rising and moving away from the equator aloft, as air moves towards the mid-latitudes, it cools and sinks leading to subsidence near the 30° parallel of both hemispheres. This circulation known as the Hadley cell forms the subtropical ridge, many of the worlds deserts are caused by these climatological high-pressure areas. Because these anticyclones strengthen with height, they are known as warm core ridges, in the absence of rotation, the wind tends to blow from areas of high pressure to areas of low pressure. The stronger the pressure difference between a system and a low-pressure system, the stronger the wind. The coriolis force caused by Earths rotation gives winds within high-pressure systems their clockwise circulation in the northern hemisphere, friction with land slows down the wind flowing out of high-pressure systems and causes wind to flow more outward from the center. High-pressure systems are associated with light winds at the surface and subsidence of air from higher portions of the troposphere. Subsidence will generally warm an air mass by adiabatic heating, thus, high pressure typically brings clear skies. Because no clouds are present to reflect sunlight during the day, there is more incoming solar radiation, at night, the absence of clouds means that outgoing longwave radiation is not blocked, giving cooler diurnal low temperatures in all seasons. If the surface level relative humidity rises towards 100 percent overnight, the movement of continental arctic air masses to lower latitudes produces strong but vertically shallow high-pressure systems
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Cyclone
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In meteorology, a cyclone is a large scale air mass that rotates around a strong center of low atmospheric pressure. A cyclone differs from a hurricane or typhoon only on the basis of location, a hurricane is a storm that occurs in the Atlantic Ocean and northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, and a cyclone occurs in the south Pacific or Indian Ocean. Cyclones are characterized by inward spiraling winds that rotate about a zone of low pressure, the largest low-pressure systems are polar vortices and extratropical cyclones of the largest scale. Warm-core cyclones such as cyclones and subtropical cyclones also lie within the synoptic scale. Mesocyclones, tornadoes and dust devils lie within the smaller mesoscale, Upper level cyclones can exist without the presence of a surface low, and can pinch off from the base of the Tropical Upper Tropospheric Trough during the summer months in the Northern Hemisphere. Cyclones have also seen on extraterrestrial planets, such as Mars. Cyclogenesis describes the process of formation and intensification. Extratropical cyclones begin as waves in large regions of enhanced mid-latitude temperature contrasts called baroclinic zones and these zones contract and form weather fronts as the cyclonic circulation closes and intensifies. Later in their cycle, extratropical cyclones occlude as cold air masses undercut the warmer air. A cyclones track is guided over the course of its 2 to 6 day life cycle by the flow of the subtropical jet stream. Weather fronts mark the boundary between two masses of air of different temperature, humidity, and densities, and are associated with the most prominent meteorological phenomena. Strong cold fronts typically feature narrow bands of thunderstorms and severe weather, such fronts form west of the circulation center and generally move from west to east, warm fronts form east of the cyclone center and are usually preceded by stratiform precipitation and fog. Warm fronts move poleward ahead of the cyclone path, occluded fronts form late in the cyclone life cycle near the center of the cyclone and often wrap around the storm center. Tropical cyclogenesis describes the process of development of tropical cyclones, Tropical cyclones form due to latent heat driven by significant thunderstorm activity, and are warm core. Cyclones can transition between extratropical, subtropical, and tropical phases, mesocyclones form as warm core cyclones over land, and can lead to tornado formation. Waterspouts can also form from mesocyclones, but more often develop from environments of high instability, henry Piddington published almost 40 papers dealing with tropical storms from Calcutta between 1835 and 1855 in The Journal of the Asiatic Society. He also coined the term cyclone, meaning the coil of a snake, in 1842, he published his landmark thesis, Laws of the Storms. There are a number of characteristics common to all cyclones
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Ecosystem of the North Pacific Subtropical Gyre
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The North Pacific Subtropical Gyre is the largest contiguous ecosystem on earth. They generally form in open ocean areas that lie between land masses. The NPSG is the largest of the gyres as well as the largest ecosystem on our planet, like other subtropical gyres, it has a high-pressure zone in its center. Circulation around the center is clockwise around this high-pressure zone, Subtropical gyres make up 40% of the Earth’s surface and play critical roles in carbon fixation and nutrient cycling. Its large size and distance from shore has caused the NPSG to be poorly sampled, the life processes in open-ocean ecosystems are a sink for the atmosphere’s increasing CO2. Gyres make up a proportion, approximately 75%, of what we refer to as the open ocean. They are considered oligotrophic, or nutrient poor because they are far from terrestrial runoff and these regions were once thought to be homogenous and static habitats. However, there is increasing evidence that the NPSG exhibits substantial physical, chemical, specifically, the NPSG exhibits seasonal and interannual variations in primary productivity, which is important for the uptake of CO2. The NPSG is not only a sink for CO2 in the atmosphere, as a direct result of this circular pattern, gyres act like giant whirlpools and become traps for anthropogenic pollutants, such as marine debris. The NPSG has become recognized for the quantity of plastic debris floating just below the surface in the center of the gyre. This area has received a lot of media attention and is commonly referred to as the Great Pacific Garbage Patch. The NPSG is not often sampled because of its distance from the coast and this perspective is derived from a dearth of comprehensive investigation of central gyre habitats. Over the past two decades these views have been challenged with an understanding of the dynamics of the NPSG. During the early days of exploration, the HMS Challenger, on its leg from Yokohama to Honolulu, collected plant. The motivation for studying open ocean ecosystems has changed over time, whereas more modern studies focus on biodiversity. Today, the Hawaii Ocean Time-series program has assembled the largest and most comprehensive data set for the NPSG and is scheduled to continue to the next millennium. Programs like HOT have debunked the hypothesis that this ecosystem is static and homogenous, the NPSG is the largest of the open ocean habitats and is considered to be the Earth’s largest contiguous biome. This great anticyclonic circulation feature extends from 15°N to 35°N latitude and its surface area spans approximately 2 x 107 km2
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