Sea level rise refers to an increase in the volume of water in the world’s oceans, resulting in an increase in global mean sea level. Sea level rise is attributed to global climate change by thermal expansion of the water in the oceans and by melting of Ice sheets. Melting of floating ice shelves or icebergs at sea raises sea levels only slightly, Sea level rise at specific locations may be more or less than the global average. Local factors might include tectonic effects, subsidence of the land, tides, currents, storms, Sea level rise is expected to continue for centuries. IPCC Summary for Policymakers, AR5,2014, indicated that the mean sea level rise will continue during the 21st century, very likely at a faster rate than observed from 1971 to 2010. A January 2017 NOAA report suggests a range of GMSL rise of 0.3 –2.5 m possible during the 21st century, Sea level rises can considerably influence human populations in coastal and island regions and natural environments like marine ecosystems. On the timescale of centuries to millennia, the melting of ice sheets could result in even higher sea level rise, partial deglaciation of the Greenland ice sheet, and possibly the West Antarctic ice sheet, could contribute 4 to 6 m or more to sea level rise. Various factors affect the volume or mass of the ocean, leading to changes in eustatic sea level. The two primary influences are temperature, and the mass of water locked up on land and sea as water in rivers, lakes, glaciers. Over much longer timescales, changes in the shape of oceanic basins. Since the Last Glacial Maximum about 20,000 years ago, sea level has risen by more than 125 m, with rates varying from tenths of a mm/yr to 10+mm/year, as a result of melting of major ice sheets. During the rest of the early Holocene, the rate of sea level rise varied from a low of about 6.0 -9.9 mm/yr to as high as 30 -60 mm/yr during brief periods of accelerated sea level rise. In sharp contrast, the period between 14,300 and 11,100 calendar years ago, which includes the Younger Dryas interval, was an interval of reduced sea level rise at about 6.0 -9.9 mm/yr. Meltwater pulse 1C was centered at 8,000 calendar years, such rapid rates of sea level rising during meltwater events clearly implicate major ice-loss events related to ice sheet collapse. The primary source may have been meltwater from the Antarctic ice sheet, other studies suggest a Northern Hemisphere source for the meltwater in the Laurentide ice sheet. For example, this research included studies of Roman wells in Caesarea and these methods in combination suggest a mean eustatic component of 0.07 mm/yr for the last 2000 years. Since 1880, as the Industrial Revolution took center stage, the ocean began to rise briskly, climbing a total of 210 mm through 2009 causing extensive erosion worldwide, Sea level rose by 6 cm during the 19th century and 19 cm in the 20th century. Evidence for this includes geological observations, the longest instrumental records, for example, geological observations indicate that during the last 2,000 years, sea level change was small, with an average rate of only 0. 0–0.2 mm per year
Close-up of Ross Ice Shelf, the largest ice shelf of Antarctica, about the size of France and up to several hundred metres thick.
Jason-1 continued the sea surface measurements begun by TOPEX/Poseidon. It was followed by the Ocean Surface Topography Mission on Jason-2, and by Jason-3