Antarctic subglacial conditions inferred from a hybrid ice sheet/ice stream model
Antarctic subglacial conditions inferred from a hybrid ice sheet/ice stream model
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DOI：
10.1016/j.epsl.2010.04.025
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发表时间：
2010-07
影响因子：
5.3
通讯作者：
F. Pattyn
中科院分区：
文献类型：
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作者：
F. Pattyn
尽管卫星观测最近取得了进展，但人们对大冰盖的冰下状况仍然知之甚少。与温度场等基本条件有关的主要不确定性是由于对地热热流的了解不足。在这里，提出了一种混合方法，利用简单的同化技术将冰盖热力学的数值模拟与先验信息结合起来。其他数据基本上是在选定地点的冰盖中测量的垂直温度分布，以及冰下湖泊的分布。通过这种方式，改进了地热热流数据集，以产生与可获得信息的地区的观测结果一致的计算温度。灵敏度实验结果表明，南极冰盖55%的搁浅部分处于压力熔点。计算的基本熔融速率约为65Gt年−1，占总表面积累的3%。尽管这些敏感性实验显示了基础融化速率的微小变化，但对基础层冰期的影响是相当重要的。在熔化速率相对较低的地区，这可能会导致标准偏差高达50%(在一个运行了106年的模型中)。冰下水流集中在南极洲大型出口冰川的下方。更大的冰下湖泊栖息在这些冰下水系的顶部。然而，一个例外是恢复冰流集水区的湖泊系统，它从上游集水区接收大量冰下融水。
Subglacial conditions of large polar ice sheets remain poorly understood, despite recent advances in satellite observation. Major uncertainties related to basal conditions, such as the temperature field, are due to an insufficient knowledge of geothermal heat flow. Here, a hybrid method is presented that combines numerical modeling of the ice sheet thermodynamics with a priori information using a simple assimilation technique. Additional data are essentially vertical temperature profiles measured in the ice sheet at selected spots, as well as the distribution of subglacial lakes. In this way, geothermal heat-flow datasets are improved to yield calculated temperatures in accord with observations in areas where information is available. Results of the sensitivity experiments show that 55% of the grounded part of the Antarctic ice sheet is at pressure melting point. Calculated basal melt rates are approximately 65Gtyear−1, which is 3% of the total surface accumulation. Although these sensitivity experiments exhibit small variations in basal melt rates, the impact on the ice age of basal layers is quite important. In areas that are characterized by relatively low melt rates, this may lead to standard deviations up to 50% (in a model run over a period of 106years). Subglacial water flow is concentrated underneath the large outlet glaciers of Antarctica. The larger subglacial lakes are perched at the head of these subglacial water systems. An exception, however, is the lake system of the Recovery Ice Stream Catchment, that receives a substantial amount of subglacial melt water from the upstream catchment.