NASA satellite reveals sea levels have risen 14mm in 17 years

Rodiano Bonacci
Mag 4, 2020

The Kangerdlugssup (pictured) and Jakobshavn glaciers in Greenland have lost roughly 14 to 20 feet (4 to 6 meters) of elevation per year over the past 16 years.

NASA said they recorded data from Ice, Cloud and Land Elevation Satellite 2 (ICESat-2), which was launched in 2018 to make detailed global altitude measurements, including over the Earth's frozen regions.

To track how the ice sheets are changing, the ICESat-2 team compared the satellite's laser scans with similar measurements that were taken by the original ICESat spacecraft from 2003 to 2009.

Greenland's ice sheet lost an average of 200 gigatons of ice a year, contributing up to two thirds of the sea level rise.

Put another way, more than 5,000 gigatons of ice has melted (a gigaton equals one billion metric tons or enough to fill 400,000 Olympic-sized swimming pools), which drove up sea levels around the world.

"ICESat-2 allows us to accurately capture subtle but important elevation changes in the vast interior of the ice sheets, a feat that was too hard for earlier satellite missions", says Csatho, PhD, chair and professor of geology in the UB College of Arts and Sciences.

The findings are based on info from the ICESat and ICESat-2 satellite laser altimeters.

The researchers used the elevation measurements from both satellites to determine how Antarctica's mass balance - the difference between accumulation and loss - changed from 2003 to 2019 for each of its 27 drainage basins.

The ice sheets are melting, and a new study research relies on state-of-the-art technology to reveal where the biggest losses are happening.

"These first results looking at land ice confirm the consensus from other research groups, but they also let us look at the details of change in individual glaciers and ice shelves at the same time", said Tom Neumann, ICESat-2 project scientist at NASA Goddard.

The data show that the continent is gaining more ice in some areas, like parts of East Antarctica. The warm air and the warming of the ocean water is also contributing to the melting.

In Greenland, there was a significant amount of thinning of coastal glaciers, Smith said. Warm ocean water undercuts floating ice shelves there and causing more ice to spill into the sea, more than offsetting the interior gains.

"It's not like any instrument that we've had in space before", said another of the authors, Alex S Gardner, a glaciologist at NASA's Jet Propulsion Laboratory in Pasadena, California. When it reaches the coast, it floats, creating ice shelves skirting around the continent.

"It's like an architectural buttress that holds up a cathedral", added co-author Helen Amanda Fricker, a glaciologist at Scripps Institution of Oceanography at the University of California. Some have rough surfaces, with crevasses and ridges, but the precision and high resolution of ICESat-2 allows researchers to measure overall changes.

This process is far more rapid in West Antarctica than in East Antarctica where it is quite patchy, with areas of thickening and thinning.

Fresh data from NASA showed clear images of Antarctica's rapidly melting ice. Smith said the satellites measure thickness of the ice sheets and shelves, but they don't capture the major iceberg calving events we've seen in recent years.

"It's like an apple tart and the ice shelves are like the wall of pastry around the edges of the tart", says Fricker. Nor do they capture the breakdown at the front of ice shelves where researchers worry ever greater walls of ice could tumble into the ocean.

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