کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6428113 | 1634730 | 2015 | 12 صفحه PDF | دانلود رایگان |
- SW Greenland marine ice-margins rapidly deglaciated 12-11 ka.
- SW Greenland land ice-margins deglaciated slowly 18-7 ka.
- Results suggest ocean environment drove rapid ice-margin retreat.
Marine-terminating outlet glaciers are a major source of modern ice loss from the Greenland Ice Sheet (GrIS), but their role in GrIS retreat during the last deglaciation is not well constrained. Here, we develop deglacial outlet glacier retreat chronologies for four regions in southwest and south Greenland to improve understanding of spatial variations in centennial- to millennial-scale ice loss under a warming climate. We calculate 10Be surface exposure ages of boulders located in fjords near the towns of Qaqortoq, Paamiut, Nuuk, and Sisimiut. Our northernmost study site, Sisimiut, deglaciated earliest at â¼18 ka to â¼15 ka with an average thinning rate of 0.1-0.3 mâyrâ1. Inland retreat from Sisimiut to the modern ice margin took â¼7 ka at an average retreat rate of 15-20 mâyrâ1. A 10Be-dated moraine â¼25 km from the modern GrIS margin deposited at â¼8 ka suggests a possible ice-margin still-stand, but this does not change overall retreat rates. After retreat from the small coastal Sisimiut fjords, the GrIS margin was mainly land-terminating in this region. In contrast, earliest exposure occurred at â¼12 ka near Qaqortoq, and 11-10 ka near Nuuk and Paamiut, with ice thinning at rates of 0.2-0.3 mâyrâ1 to instantaneous within measurement uncertainty. Ice retreat inland through the extensive Nuuk, Paamiut, and Qaqortoq fjord systems to near modern ice margins occurred in <1 ka, resulting in minimum retreat rates of 25-65 mâyrâ1 and maximum retreat rates of â¼95 mâyrâ1 to instantaneous within the uncertainty of our measurements. This rapid thinning and retreat of marine-terminating southwest GrIS margins is contemporaneous with an incursion of relatively warm ocean waters into the Labrador Sea and toward the southwest Greenland coast, suggesting that a warming ocean may have contributed to the more rapid retreat of marine GrIS termini in the Nuuk, Paamiut, and Qaqortoq fjord systems relative to the slower ice retreat inland from Sisimiut. Our results highlight past outlet glacier-ocean interaction as a potentially important driver in rapid GrIS retreat.
Journal: Earth and Planetary Science Letters - Volume 426, 15 September 2015, Pages 1-12