The Greenland Ice Sheet 811 General features

The Greenland Ice Sheet (Figure 8.1) is by far the largest terrestrial ice mass in the Arctic and is the second largest in the world (following the Antarctic Ice Sheet). The ice sheet covers an area of 1.71 x 106 km2. Other glaciers and ice caps on Greenland cover a further 0.049 x 106 km2 (Table 2.2). The ice sheet reaches a maximum elevation of 3208 m at Summit (72.6° N, 37.5° W). A secondary elevation maximum on the southern part of the ice sheet rises to about 2800 m. The surface slope over most of the Greenland Ice Sheet is barely 1 degree, but is much greater at the margins. The margins of the ice sheet are also characterized by numerous fiords and associated valley glaciers that drain the ice sheet. Greenland is the source of most of the icebergs found in the North Atlantic. The maximum ice thickness has recently been estimated at 3367 m. The estimated ice volume is 2.93 x 106km3 (Bamber et al., 2001). With adjustment for isostatic rebound, the water locked up in the Greenland Ice Sheet corresponds to an approximate global sea level equivalent of 7.2 m. By comparison, the much larger Antarctic Ice Sheet, which covers about 12.4 x 106 km2 with a volume of 25.7 x 106 km3,

Isostatic Rebound
Figure 8.1 The location of GC-Net automatic weather stations in Greenland (+) and coastal settlements (°) (from Steffen and Box, 2001, by permission of AGU).

contains an adjusted 61.1 m of sea level equivalent (Huybrechts et al., 2001). Nevertheless, we are obviously dealing with a large amount of ice.

Zwally and Giovinetto (2001) estimate that, at present, 88% of the coterminous ice sheet lies in the accumulation zone (where annual mass gains exceed mass losses), with the other 12% lying in the ablation zone (where annual mass losses exceed mass gains). Assessing the mass balance of the ice sheet is an active area of research. It appears that while the higher portions of the ice sheet are in approximate mass balance, lower coastal areas thinned in the 1990s, with the coastal mass losses contributing to sea level rise (Thomas, 2001).

Climate data for Greenland are available from several field programs. Beginning in 1987, an automatic weather station (AWS) network was established in Greenland by C. R. Stearns. Data from these stations provide a valuable addition to the few previous expedition measurements discussed by Putnins (1969) and Barry and Kiladis (1982). Since 1995, extensive climatic data have been collected by AWSs through NASA's Program for Arctic Regional Climate Assessment (PARCA) (Steffen et al., 1996; Thomas, 2001). The Greenland Climate Network (GC-Net) established under PARCA provides hourly climatic data from 18 AWSs. The sites are distributed to sample from different climatic zones (Figure 8.1) and range in altitude from 568 m (JAR-2) to 3208 m (Summit).

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