Bjerknes Centre for Climate Research, Allégaten 70, N-5007, Bergen, Norway.
Department of Earth Science, University of Bergen, Allégaten 41, N-5020, Bergen, Norway.
Sci Rep. 2021 Apr 16;11(1):8361. doi: 10.1038/s41598-021-87317-5.
The accelerated melting of ice on the Antarctic Peninsula and islands in the sub-Antarctic suggests that the cryosphere is edging towards an irreversible tipping point. How unusual is this trend of ice loss within the frame of natural variability, and to what extent can it be explained by underlying climate dynamics? Here, we present new high-resolution reconstructions of long-term changes in the extents of three glaciers on the island of South Georgia (54°S, 36°W), combining detailed analyses of glacial-derived sediments deposited in distal glacier-fed lakes and cosmogenic exposure dating of moraines. We document that the glaciers of South Georgia have gradually retracted since the Antarctic cold reversal (ACR, 14.5-12.8 ka), culminating in the disappearance of at least one of the reconstructed glaciers. The glacier retreat pattern observed in South Georgia suggests a persistent link to summer insolation at 55°S, which intensified during the period from the ACR to approximately 2 ka. It also reveals multi-decadal to centennial climate shifts superimposed on this long-term trend that have resulted in at least nine glacier readvances during the last 10.5 ka. Accompanying meridional changes in the Southern Hemisphere westerlies and their interconnection with local topography may explain these glacier readvances.
南极半岛和亚南极岛屿的冰加速融化表明，冰冻圈正逐渐接近不可逆转的临界点。在自然变化的范围内，这种冰损失趋势有多罕见？在多大程度上可以用潜在的气候动态来解释？在这里，我们结合对沉积在遥远冰川补给湖泊中的冰川衍生沉积物的详细分析和对冰碛物的宇宙成因暴露测年，为南乔治亚岛（54°S，36°W）的三条冰川的长期变化提供了新的高分辨率重建。我们记录到，自南极冷反转（ACR，14.5-12.8ka）以来，南乔治亚岛的冰川逐渐退缩，最终至少有一条重建的冰川消失。南乔治亚岛观察到的冰川退缩模式表明与 55°S 的夏季太阳辐射存在持续联系，这种联系在 ACR 到大约 2ka 期间增强。它还揭示了叠加在这一长期趋势上的数十年到百年的气候变化，导致了过去 10.5ka 中至少九次冰川的重新扩张。南半球西风的纬向变化及其与当地地形的相互联系可能解释了这些冰川的重新扩张。
