A continuum model (PSUMEL1) of ice melange and its role during retreat of the Antarctic Ice Sheet
A continuum model (PSUMEL1) of ice melange and its role during retreat of the Antarctic Ice Sheet
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DOI：
10.5194/gmd-11-5149-2018
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发表时间：
2018-12-20
影响因子：
5.1
通讯作者：
Alley, Richard B.
中科院分区：
文献类型：
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作者：
Pollard, David;DeConto, Robert M.;Alley, Richard B.
快速后退的厚冰锋会产生大量的混合物（浮冰碎片），这可能会影响南极海冰的快速后退。在现代格陵兰峡湾，混杂岩对崩解的冰面提供了巨大的背压，减缓了冰锋崩解的速度。在南极洲西部更大的范围内，尚不清楚美琅脂是否会堵塞航道，并提供足够的背压，作为一个负反馈，减缓撤退。在这里，我们描述了一个新的混杂岩模型，使用连续力学公式，计算上是可行的长期南极大陆的应用。它是在一个理想化的矩形通道进行测试和校准非常基本上使用观测到的现代条件在雅各布港峡湾，西格陵兰岛。然后，该模型被应用到南极冰的急剧退缩，以应对温暖的上新世中期气候。由于混杂岩参数值产生了合理的现代雅各布港结果，南极海冰在上新世模拟中仍然急剧退缩，尽管产生了大量的混杂岩，但几乎没有减缓。这既适用于西南极洲的快速早期崩溃，也适用于后来退缩到主要的东南极洲盆地。如果改变参数值，使混杂岩对流动的阻力更大，远远超出合理的雅各布港结果的范围，西南极洲仍然崩溃，只有少数东南极洲盆地的退缩减缓或阻止。
Rapidly retreating thick ice fronts can generate large amounts of melange (floating ice debris), which may affect episodes of rapid retreat of Antarctic marine ice. In modern Greenland fjords, melange provides substantial back pressure on calving ice faces, which slows ice front calving rates. On the much larger scales of West Antarctica, it is unknown if melange could clog seaways and provide enough back pressure to act as a negative feedback slowing retreat. Here we describe a new melange model, using a continuum-mechanical formulation that is computationally feasible for long-term continental Antarctic applications. It is tested in an idealized rectangular channel and calibrated very basically using observed modern conditions in Jakobshavn fjord, West Greenland. The model is then applied to drastic retreat of Antarctic ice in response to warm mid-Pliocene climate. With melange parameter values that yield reasonable modern Jakobshavn results, Antarctic marine ice still retreats drastically in the Pliocene simulations, with little slowdown despite the huge amounts of melange generated. This holds both for the rapid early collapse of West Antarctica and for later retreat into major East Antarctic basins. If parameter values are changed to make the melange much more resistive to flow, far outside the range for reasonable Jakobshavn results, West Antarctica still collapses and retreat is slowed or prevented only in a few East Antarctic basins.