Warming seas are accelerating the retreat of Greenland’s coastal glaciers.
Sverdrup Glacier in northwest Greenland is really normal. It is a textbook illustration of the several coastal glaciers all over the island that circulation into deep fjords. But Sverdrup also represents a significant course of Greenland glaciers that are undergoing swift retreat in response to heat ocean h2o.
This picture, obtained by the Operational Land Imager (OLI) on Landsat 8, exhibits Sverdrup Glacier on September 21, 2020. Strains point out the retreating place of the glacier front considering the fact that 2000.
The posture in 2000 was identical to the mid-1980s, indicating that there experienced been a period of time of balance when ocean temperatures were great. Then, between 1998 and 2007, waters all-around Greenland warmed rapidly—almost 2 levels Celsius—and the glacier commenced to slim, flow faster, and retreat.
“Sverdrup Glacier’s retreat and ice decline was ‘triggered’ by heat h2o,” explained Michael Wooden, a postdoctoral researcher at NASA’s Jet Propulsion Laboratory (JPL). “It is one of lots of deep glaciers that are now in an unstable configuration, and will probably continue to retreat for a lot of yrs, no make a difference what the ocean does.”
To assess how warming ocean water affects coastal glaciers, scientists with the Oceans Melting Greenland (OMG) mission have been learning these maritime-terminating glaciers from the air and by ship. In a recent analyze led by Wooden, researchers utilised these info to display that when it comes to glacier melting, the depth of the fjord matters.
Glaciers in deep fjords occur into make contact with with far more heat ocean drinking water than glaciers in shallow fjords. This hastens undercutting—a procedure in which a layer of warm, salty water at the bottom of a fjord melts the base of a glacier, resulting in the ice previously mentioned to split apart.
Of the 226 glaciers surveyed, 74 in deep fjords accounted for approximately 50 % of the full ice decline from Greenland involving 1992 and 2017. These glaciers exhibited the most undercutting. In contrast, the 51 glaciers that lengthen into shallow fjords or onto shallow ridges knowledgeable the least undercutting and contributed only 15 percent of the full ice decline.
“We have regarded for perfectly more than a decade that the warmer ocean plays a important function in the evolution of Greenland glaciers,” claimed Eric Rignot, OMG deputy principal investigator at JPL. “But for the very first time, we have been equipped to quantify the undercutting effect and display its dominant impression on the glacier retreat about the past 20 yrs.”
These findings recommend that local weather styles might underestimate glacial ice loss by at the very least a issue of two if they don’t account for undercutting by a heat ocean.
The analyze also lends perception into why quite a few of Greenland’s glaciers never recovered following the abrupt warming of ocean water between 1998 and 2007. Although ocean warming paused concerning 2008 and 2017, the glaciers experienced currently experienced this kind of extraordinary undercutting in the previous ten years that they continued to retreat at an accelerated fee.
“When the ocean speaks, the Greenland Ice Sheet listens,” stated OMG Principal Investigator Josh Willis, also of JPL. “This gang of 74 glaciers in deep fjords is seriously experience the affect of the ocean it’s discoveries like these that will finally assistance us forecast how rapid the ice will shrink. And which is a essential resource for both of those this technology and the subsequent.”
NASA Earth Observatory impression by Joshua Stevens, working with Landsat data from the U.S. Geological Study and details courtesy of Wood, M. et al. (2021). Story by Kathryn Hansen and Ian O’Neill.