Shift in Melting Pattern of the Greenland Ice Sheet Likely to Occur

Surface ice melt will become the new form of dominant ice melt in Greenland as outlet glaciers retreat inland, leaving ice production in second place, according to a new study.

The Greenland ice sheet is often considered an important potential contributor to future global sea-level rise over the next century or longer: in total, levels would rise by more than 23 feet (seven meters) if it completely melted, scientists estimate. Changes in its total mass are governed by both fluctuations in melting and snowfall on its surface, in addition to changes to the number of icebergs released into the ocean from a large number of outlet glaciers.

Over the last decade, the ice loss from the ice sheet has been increasing, with half of it attributed to changes in surface conditions and the remainder due to increased iceberg calving.

Researchers from the Vrije Universiteit Brussel, funded by ice2sea, a European Union project, decided to study how both processes will evolve and interact in the future, which they did using a computer model that projects the future ice sheet evolution with high accuracy via the latest available techniques and input data, according to the scientists.

The group devised a method to generalize projections made in earlier research that concerned just four of Greenland's outlet glaciers. In doing so, they were able to apply the earlier findings to all calving glaciers around the Greenland ice sheet.

Their results point to a total sea-level contribution from the Greenland ice sheet for an average warming scenario after 100 and 200 years of 7 and 21 centimeters (3 to 8 inches), respectively.

However, the balance between the two processes is changing in the future so that iceberg calving may only account for between 6 percent and 18 percent of the sea-level contribution after 200 years, the scientists determined.

The reason this is important, they explained, is because variations in outlet glacier dynamics have often been suspected to have the potential for very large sea-level contributions.

"Our research has shown that the balance between the two most important mass loss processes will change considerably in the future so that changes in iceberg calving only account for a small percentage of the sea-level contribution after 200 years with the large remainder due to changes in surface conditions," lead author Dr Heiko Goelze of the Vrije Universiteit Brusse said in a press release.

However, warns David Vaughan of the British Antarctic Survey, this is no reason to get complacent, explaining that the reason calving glaciers will decrease in comparison to surface melt is because "so much ice will be lost in coming decades that many glaciers currently sitting in fjords will retreat inland to where they are no longer affected by warming seas around Greenland."