What Greenland’s ice loss means for oceans

The Greenland ice sheet has lost 20 percent more ice than scientists previously thought, posing potential problems for ocean circulation patterns and sea level rise, according to a new study.

Researchers had previously estimated that the Greenland ice sheet lost about 5,000 giga-tons of ice in recent decades, enough to cover Texas in a sheet 26 feet high. The new estimate adds 1,000 giga-tons to that period, the equivalent of piling about 5 more feet of ice on top of that fictitious Texas-sized sheet.

The additional loss comes from an area previously unaccounted for in estimates: ice lost at a glacier’s edges, where it meets the water. Before this study, estimates primarily considered mass changes in the interior of the ice sheet, which are driven by melting on the surface and glaciers thinning from their base on the ice sheet.

The study provides improved measurements of ice loss and meltwater discharge in the ocean, which can advance sea level and ocean models.

Loss from the edges of glaciers won’t directly affect sea level rise because they usually sit within deep fjords below sea level, but the freshwater melt could affect ocean circulation patterns in the Atlantic Ocean.

“We can take a look at the glaciers we have now and see how they’re behaving,” said Michael Wood, a study co-author and glaciologist. “That will give us a sense of what the future might hold for future ice loss from Greenland.”

Glaciers can lose ice in many ways. One change can happen when large ice chunks break off at the edge, known as calving. They can also lose ice when it melts faster than it can form, causing the end of a glacier to retreat and move to higher elevations.

Scientists found that a total of 1,034 giga-tons of ice was lost across all glaciers because of this retreat and calving on their peripheries. The loss accelerated since January 2000, with the glaciers losing a total of 42 giga-tons each year. It has shown no signs of slowing down.