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Sensitivity, stability and future evolution of the world’s northernmost ice cap, Hans Tausen Iskappe (Greenland)

Tijdschriftbijdrage - Tijdschriftartikel

In this study the dynamics and sensitivity of Hans Tausen Iskappe (western Peary Land, Greenland) to climatic forcing is investigated with a coupled ice flow – mass balance model. The surface mass balance is calculated from a precipitation field obtained from the Regional Climate Model RACMO2.3, while runoff is calculated from a Positive Degree-Day runoff/retention model. For the ice flow a 3-D higher-order thermo-mechanical model is used, which is run at a 250 m resolution. A higher-order solution is needed to accurately represent the ice flow in the outlet glaciers. Under 1961-1990 climatic conditions a steady state ice cap is obtained that is overall similar in geometry to the present-day ice cap. Ice thickness, temperature and flow velocity in the interior agree well with observations. For the outlet glaciers a reasonable agreement with temperature and ice thickness measurements can be obtained with an additional heat source related to infiltrating meltwater. The simulations indicate that the SMB-elevation feedback has a major effect on the ice cap response time and stability. This causes the southern part of the ice cap to be extremely sensitive to a change in climatic conditions and leads to thresholds in the ice cap evolution. Under constant 2005-2014 climatic conditions the entire southern part of the ice cap cannot be sustained and the ice cap loses about 80% of its present-day volume. The projected loss of surrounding permanent sea-ice and resultant precipitation increase may attenuate the future mass loss, but will be insufficient to preserve the present-day ice cap for most scenarios. In a warmer and wetter climate the ice margin will retreat while the interior is projected to thicken, leading to a steeper ice cap, in line with the present-day observed trends. For intermediate (+4°C) and high warming scenarios (+8°C) the ice cap is projected to disappear around 2400 and 2200 A.D. respectively, almost independent of the projected precipitation regime and the simulated present-day geometry.
Tijdschrift: Cryosphere
ISSN: 1994-0416
Issue: 2
Volume: 11
Pagina's: 805-825
Aantal pagina's: 26
Jaar van publicatie:2017
Trefwoorden:Geowetenschappen en technologie