Modelling West Antarctic ice sheet growth and collapse through the past five million years
Modelling West Antarctic ice sheet growth and collapse through the past five million years
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DOI：
10.1038/nature07809
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发表时间：
2009-03-19
期刊：
影响因子：
64.8
通讯作者：
DeConto, Robert M.
中科院分区：
文献类型：
--
作者：
Pollard, David;DeConto, Robert M.
南极西部冰盖（WAIS）的冰量相当于海平面5米（1），长期以来一直被认为能够在过去和未来发生灾难性的崩溃（2-4）。今天，冰盖的边缘是脆弱的漂浮冰架，这些冰架支撑着内陆冰流的快速流动。接地线位于海平面以下几百米处，河床在上游加深，增加了失控撤退的前景（3，5）。对未来WAIS行为的预测受到了对过去变化及其潜在强迫机制的有限理解的阻碍（6，7）。它自末次盛冰期以来的变化是最为人所知的，接地线大约在15 kyr前前进到大陆架边缘，然后在3 kyr前退回到近现代的位置（8）。海平面和深海岩芯同位素记录以及冰下沉积物中开阔海洋硅藻的发现间接地表明，在上新世早期温暖时期（9）和一些更新世间冰期（10）之前的崩塌。然而，到目前为止，这种行为的直接证据很少。在这里，我们使用了一个冰盖/冰架组合模型（12），能够高分辨率嵌套，并对接地线动力学和冰架支撑进行了新的处理，以模拟过去500万年来南极冰盖的变化。模拟的WAIS变化范围从完整的冰川范围与大陆架断裂附近的接地线，类似于现代的中间状态，以及短暂但戏剧性的撤退，只留下小的，孤立的冰盖在南极洲西部岛屿。冰川、中间状态和崩塌状态之间的转变相对较快，需要一到几千年。我们的模拟与从罗斯海西部恢复的新沉积物记录（ANDRILL AND-1B）非常一致（11），表明从更频繁的崩塌到更多的冰川状态的长期趋势，上新世占主导地位的40-kyr旋回，以及海洋同位素阶段31（类似于107万年前）和其他超级间冰期的主要退缩。
The West Antarctic ice sheet (WAIS), with ice volume equivalent to similar to 5 m of sea level(1), has long been considered capable of past and future catastrophic collapse(2-4). Today, the ice sheet is fringed by vulnerable floating ice shelves that buttress the fast flow of inland ice streams. Grounding lines are several hundred metres below sea level and the bed deepens upstream, raising the prospect of runaway retreat(3,5). Projections of future WAIS behaviour have been hampered by limited understanding of past variations and their underlying forcing mechanisms(6,7). Its variation since the Last Glacial Maximum is best known, with grounding lines advancing to the continental-shelf edges around similar to 15 kyr ago before retreating to near-modern locations by similar to 3 kyr ago(8). Prior collapses during the warmth of the early Pliocene epoch(9) and some Pleistocene interglacials have been suggested indirectly from records of sea level and deep-sea-core isotopes, and by the discovery of open-ocean diatoms in subglacial sediments(10). Until now(11), however, little direct evidence of such behaviour has been available. Here we use a combined ice sheet/ice shelf model(12) capable of high-resolution nesting with a new treatment of grounding-line dynamics and ice-shelf buttressing 5 to simulate Antarctic ice sheet variations over the past five million years. Modelled WAIS variations range from full glacial extents with grounding lines near the continental shelf break, intermediate states similar to modern, and brief but dramatic retreats, leaving only small, isolated ice caps on West Antarctic islands. Transitions between glacial, intermediate and collapsed states are relatively rapid, taking one to several thousand years. Our simulation is in good agreement with a new sediment record (ANDRILL AND-1B) recovered from the western Ross Sea(11), indicating a long-term trend from more frequently collapsed to more glaciated states, dominant 40-kyr cyclicity in the Pliocene, and major retreats at marine isotope stage 31 (similar to 1.07 Myr ago) and other super-interglacials.