Subtleties in Greenland melting, according to scientists

Terra Daily via Agence France-Presse: The recent acceleration of glacier melt-off in Greenland, which some scientists fear could dramatically raise sea levels, may only be a temporary phenomenon, according to a study published Sunday. Researchers in Britain and the United States devised computer models to test three scenarios that could account for rapid -- by the standards applied to glaciers -- melting of the Helheim Glacier, one of Greenland's largest.

Two were based on changes caused directly by global warming: an increase in the flow of water that greases the underbelly of the glacier as it slides toward the sea, and a general thinning due to melting. If confirmed, either of these explanations would point to a sustained increase in runoff over the coming decades, fueling speculation that sea level could rise faster and higher than once thought.

The stakes are enormous: the rate at which the global ocean water mark rises could have a devastating impact on hundreds of millions of people living in low-lying areas around the world. But a team led by Faezeh Nick of Durham University in Britain found that neither of these scenarios matched the data.

By contrast, the third computer model -- which hypothesised that melt-off was triggered by changing conditions in the confined area where the glacier meets the sea -- fit like a glove, he said. "Whatever happens at the terminus provokes a strong and rapid reaction in the rest of the glacier. The result has been a significant loss of mass" as huge chunks of ice drop into the ocean, a process known as calving, Vieli explained.

These changes are also set in motion by global warming, but are not likely to last, he said. "You cannot maintain these very high rates of peak mass loss for very long. The glaciers start to retreat and settle into a new an relatively stable state," he said.

Vieli cautioned that his findings, published in Nature Geoscience, are narrowly focused on one glacier, and that sea levels could still rise higher than the IPCC's original projections. Other Greenland glaciers behave differently, and the dynamics of the Antarctic ice sheet are still poorly understood, he noted. Nor should the new study "be taken out of context to suggest that climate change is not a serious threat -- it is," he added....

The north of Kejser Franz Josef Fjord near Stensjö Bjerg, shot by Erik Christensen, Wikimedia Commons, under the terms of the GNU Free Documentation License, Version 1.2