Greenland Warming

The Greenland ice sheet is the second largest ice mass on Earth and is about one-tenth the volume of the Antarctic ice sheet. It is the only significant ice mass in the Arctic today. [ See Antarctica and Climate Change ; and Ice Sheets .] It is an ice-age relict that overlies a bowl-shaped continent almost completely fringed by coastal mountains.

PHYSICAL-GEOGRAPHIC SETTING

The ice sheet extends from about 60° to 83°N over a distance of 2,400 km in the North Atlantic Ocean. The ice sheet covers 1.71 million km2 , or roughly 80% of the surface of Greenland. It consists of a northern dome and a southern dome, with maximum elevations of 3,230 m and 2,850 m, respectively, linked by a long saddle with elevations around 2,500 m. Its total volume is about 2.85 million km3, which, if it were to melt entirely, would raise global sea level by about 7.2 m. The ice sheet has an average thickness of 1,670 m and reaches a maximum of 3,300 m in the center. The bedrock surface below the ice sheet is an extensive flat area near sea level, which would rebound by as much as 1,000 m if the ice sheet were to be removed (Figure 1). Precipitation over Greenland generally decreases from south to north, ranging from about 2,500 mm per year in the southeast to less than 150 mm per year in interior northeastern Greenland. The southern high precipitation zone is largely determined by the Icelandic low and the resulting onshore flow which is forced to ascend the surface of the ice sheet. In contrast to Antarctica, summer temperatures on Greenland are high enough to cause widespread summer melting. This results in an ablation zone with negative mass balance all around its perimeter. Ablation rates are highest over the southwestern part of the ice sheet where...

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... might not develop back to normal conditions, in which case the demise of the Greenland ice sheet and the associated sea-level rise might be irreversible. For this reason, the Greenland ice sheet is often described as a relict ice mass. It survived the current Holocene interglacial solely because it creates its own cold surface-climate because of its elevation. The last time Greenland temperatures were several degrees higher than today was the last interglacial 125,000 years ago. Ice core evidence for a smaller ice sheet is consistent with the observation that sea level then was several meters higher than today. At that time, the ice sheet did not disappear completely, probably because the warming was not strong enough and did not last long enough. The ice sheet was probably saved from extinction by the onset of the last glacial period several thousand years later.