These new maps show 16 years of ice sheet loss

Rodiano Bonacci
Mag 3, 2020

As the ice melts in Greenland and Antarctica, the water surges toward the Equator where sea-level rise is already two to three times as fast as the global average.

The study used an advanced Earth-observing satellite launched by U.S. space agency Nasa which bounces laser pulses off the ice surface to help measure changes in the Greenland and Antarctic ice sheets over 16 years.

As the climate has warmed, Antarctica and Greenland have lost enough ice in the last 16 years to fill Lake Michigan, according to results from a new NASA mission.

Climate change is reshaping ice sheets in the Arctic and Antarctic, and NASA's ICESat and ICESat-2 satellites help researchers determine what those alterations look like. By comparing the recent data with measurements taken by the original ICESat from 2003 to 2009, researchers have generated a comprehensive portrait of the complexities of ice sheet change and insights about the future of Greenland and Antarctica.

Media captionWhy is Antarctica's mighty Thwaites Glacier melting? "How much ice we are going to lose, and how quickly we are going to lose it, is a really key thing that needs to be understood, so that we can plan".

Using data from the ICESat and ICESat-2 laser altimeters, scientists precisely measured how much ice has been lost from ice sheets in Antarctica and Greenland between 2003 and 2019.

According to NASA, the amount of ice lost can cover Central Park in NY with a thickness of more than 1,000 feet, reaching higher than the Chrysler Building. For the Science study, they fed the readings from ICESat and ICESat-2 into a computer model that converted changes in volume into changes in mass.

If found the loss of ice from Antarctica and Greenland outweighs gains from accumulated snow. And with some ice shelves retreating in area in the intervening years, there will be mass losses that have simply been omitted from the calculations.

In Greenland, there was a significant amount of thinning of coastal glaciers, Smith said.

Alex Gardner, a glaciologist from NASA's Jet Propulsion Laboratory in Southern California and coauthor of the Science paper, told NASA that the new analysis reveals the response of the ice sheets to climate change in great detail, revealing clues as to why and how the caps polar bears are reacting as they are.

The majority of Antarctica's contribution to sea level rise comes from its glaciers flowing into the ocean as warmer water erodes the ice. The Kangerdulgssuaq and Jakobshavn glaciers, for example, have lost 14 to 20 feet (4 to 6 meters) of elevation per year - the glacial basins have lost 16 gigatons per year and 22 gigatons per year, respectively.

Glaciologist Matt King said a strength of this research is that it observed both grounded ice such as glaciers and land ice extending onto the sea, whereas previous studies focused on just one or the other.

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

Dr Anna Hogg works with European satellite systems that measure the shape of the ice sheets with radar instruments.

Study co-author Helen Amanda Fricker of the University of California said land-based ice that extends out to sea has previously been excluded because melting ice on land directly contributes to sea level rises, whereas ice that floats on water does not.

"It's exciting to see how IceSat-2's new high-resolution laser can be used to peer into 80m-deep crevasses in Antarctica, like those on the Ross Ice Shelf", she told BBC News.

The latest data showed melting was more extreme in Greenland than in Antarctica.

The data show that the continent is gaining more ice in some areas, like parts of East Antarctica.

There, floating ice shelves are melting as a result of warmer oceans, which is letting more ice from glaciers and ice sheets behind flow out into the ocean, the researchers said. Increased precipitation in the form of snow leads to an increase in ice sheet mass because as snow compresses over time it turns to ice. Those shelves are natural barriers that slow the rate of ice loss, but as they melt in a warming ocean, that barrier is shrinking.

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