Greenland's Contribution to Sea-Level Rise May Be Much Larger Than Expected

Two new studies are offering new warnings about the Greenland ice sheet and its future contribution to rising sea levels that could wreak havoc on coastal areas.

In one, published in Proceedings of the National Academy of Sciences, researchers report that current computer models are not fully capturing how Greenland's glaciers are changing with warming and adding to ocean levels, particularly in the southeast part of the ice sheet.  The other study, in Nature Climate Change, reveals that "supraglacial" lakes that can speed up ice loss could double their reach on Greenland by 2060 as they move further inland.

While they are from different journals, both papers have a parallel subtext that current projections of Greenland and sea-level rise are likely underestimating ice loss, and perhaps to a large degree.

"The pattern of changes are much more complex than we expected ... and the complexity is not considered in the projections yet," said Beata Csatho, an associate professor of geology at the University of Buffalo and author of the PNAS paper.

'Big changes' in little-studied area

Rather, ice loss from small glaciers in the southeast part of the ice sheet constituted more than 40 percent of Greenland's ice loss during the study period, even though much of the area has often been ignored in modeling.  "We are detecting very rapid and big changes there," said Csatho.  That is a concern because the shedding is likely to continue, even though it's not adequately considered now in projections, she said.

Because the southeast has small glaciers, it has been difficult to study in many locations despite its importance, added Cornelius van der Veen, a geography professor at University of Kansas and study co-author.

The team also found increasing mass loss in north and northeast Greenland, where ice projections have been based on the Petermann Glacier, which actually did not undergo much change during the study period, said Csatho.  That further signals that projections of the future of ice loss from that part of the ice sheet may be on the low side, she said.

"Here, a few decades of continuing thinning could unground large regions, which could ultimately cause significant mass loss from the deep, central part of the ice sheet," she said.

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