First outcomes from NASA’s ICESat-2 mission map 16 years of melting ice sheets

College of Washington

IMAGE: This exhibits the quantity of ice gained or misplaced by Antarctica between 2003 and 2019. Darkish reds and purples present giant common charges of ice loss close to the coasts, whereas… view extra  Credit score: Smith et al./Science

Utilizing essentially the most superior Earth-observing laser instrument NASA has ever flown in house, a crew of scientists led by the College of Washington has made exact measurements of how the Greenland and Antarctic ice sheets have modified over 16 years.

In a brand new research printed within the journal Science on April 30, scientists discovered the web lack of ice from Antarctica, together with Greenland’s shrinking ice sheet, has been chargeable for zero.55 inches (14 millimeters) of sea degree rise to the worldwide ocean since 2003. In Antarctica, sea degree rise is being pushed by the lack of the floating ice cabinets melting in a warming ocean. The ice cabinets assist maintain again the circulate of land-based ice into the ocean.

The findings come from the Ice, Cloud and land Elevation Satellite tv for pc 2 (ICESat-2), which was launched into orbit in fall 2018 and commenced taking detailed world elevation measurements, together with over Earth’s frozen areas. By evaluating the brand new knowledge with measurements taken by the unique ICESat from 2003 to 2009, researchers have generated a complete portrait of the complexities of ice sheet change – and insights into the way forward for Greenland and Antarctica.

“If you happen to watch a glacier or ice sheet for a month, or a yr, you’re not going to study a lot about what the local weather is doing to it,” stated lead writer Benjamin Smith, a glaciologist on the College of Washington. “We now have a 16-year span between ICESat and ICESat-2 and will be rather more assured that the adjustments we’re seeing within the ice must do with the long-term adjustments within the local weather. And ICESat-2 is a extremely outstanding software for making these measurements. We’re seeing high-quality measurements that carpet each ice sheets, which allow us to make an in depth and exact comparability with the ICESat knowledge.”

Earlier research of ice loss or achieve usually analyze knowledge from a number of satellites and airborne missions. The brand new research takes a single sort of measurement – top as measured by an instrument that bounces laser pulses off the ice floor – offering essentially the most detailed and correct image of ice sheet change up to now.

The researchers took tracks of ICESat measurements and overlaid the denser tracks of ICESat-2 measurements from 2019. The place the 2 knowledge units intersected – tens of tens of millions of websites – they ran the info by means of laptop applications that accounted for the snow density and different elements, after which calculated the mass of ice misplaced or gained.

“The brand new evaluation reveals the ice sheets’ response to adjustments in local weather with unprecedented element, revealing clues as to why and the way the ice sheets are reacting the best way they’re”, stated co-author Alex Gardner, a glaciologist at NASA’s Jet Propulsion Laboratory in Pasadena, California.

The research discovered that Greenland’s ice sheet misplaced a mean of 200 gigatons of ice per yr, and Antarctica’s ice sheet misplaced a mean of 118 gigatons of ice per yr. One gigaton of ice is sufficient to fill 400,000 Olympic-sized swimming swimming pools.

Of the ocean degree rise that resulted from ice sheet meltwater and iceberg calving, about two-thirds of it got here Greenland, the opposite third from Antarctica, Smith and his colleagues discovered.

“It was wonderful to see how good the ICESat-2 knowledge appeared, proper out of the gate,” stated co-author Tom Neumann at NASA’s Goddard House Flight Heart in Greenbelt, Maryland. “These first outcomes taking a look at land ice affirm the consensus from different analysis teams, however additionally they allow us to take a look at the main points of change in particular person glaciers and ice cabinets on the identical time.”

In Greenland, there was a big quantity of thinning of coastal glaciers, Smith stated. The Kangerlussuaq and Jakobshavn glaciers, for instance, have misplaced 14 to 20 toes (four to six meters) of elevation per yr. Hotter summer season temperatures have melted ice from the floor of the glaciers and ice sheets, and in some locations hotter ocean water erodes away the ice at their fronts.

In Antarctica, the dense tracks of ICESat-2 measurements confirmed that the ice sheet is getting thicker in elements of the continent’s inside, doubtless because of elevated snowfall, Smith stated. However the lack of ice from the continent’s margins, particularly in West Antarctica and the Antarctic Peninsula, far outweighs any beneficial properties within the inside. In these locations, the ocean can also be more likely to blame.

“In West Antarctica, we’re seeing a number of glaciers thinning very quickly,” Smith stated. “There are ice cabinets on the downstream finish of these glaciers, floating on water. And people ice cabinets are thinning, letting extra ice circulate out into the ocean as the hotter water erodes the ice.”

These ice cabinets, which rise and fall with the tides, will be tough to measure, stated co-author Helen Amanda Fricker, a glaciologist at Scripps Establishment of Oceanography on the College of California, San Diego. A few of them have tough surfaces, with crevasses and ridges, however the precision and excessive decision of ICESat-2 permits researchers to measure total adjustments, with out worrying about these options skewing the outcomes.

This is likely one of the first occasions that researchers have measured lack of the floating ice cabinets round Antarctica concurrently with lack of the continent’s ice sheet.

Ice that melts from ice cabinets doesn’t increase sea ranges, because it’s already floating – identical to an ice dice in a full cup of water doesn’t overflow the glass. However the ice cabinets do present stability for the glaciers and ice sheets behind them.

“It’s like an architectural buttress that holds up a cathedral,” Fricker stated. “The ice cabinets maintain the ice sheet up. If you happen to take away the ice cabinets, and even for those who skinny them, you’re lowering that buttressing pressure, so the grounded ice can circulate quicker.”

The researchers discovered ice cabinets in West Antarctica, the place lots of the continent’s fastest-moving glaciers are positioned, are shedding mass. Patterns of thinning present that Thwaites and Crosson ice cabinets have thinned essentially the most, a mean of about 5 meters (16 toes) and three meters (10 toes) of ice per yr, respectively.

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The research was funded by NASA. Different co-authors are Johan Nilsson and Fernando Paolo at NASA’s Jet Propulsion Laboratory; Brooke Medley, Thorsten Markus and H. Jay Zwally at NASA’s Goddard House Flight Heart; Nicholas Holschuh at Amherst School; Susheel Adusumilli on the College of California, San Diego; Kelly Brunt on the College of Maryland; Bea Csatho on the College of Buffalo; Kaitlin Harbeck at KBR; and Matthew Siegfried on the Colorado Faculty of Mines.

From EurekAlert!

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