Jordan T A, Martin C, Ferraccioli F, Matsuoka K, Corr H, Forsberg R, Olesen A, Siegert M
British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK.
Norwegian Polar Institute, Tromsø, Norway.
Sci Rep. 2018 Nov 14;8(1):16785. doi: 10.1038/s41598-018-35182-0.
Melting at the base of the Antarctic Ice Sheet influences ice dynamics and our ability to recover ancient climatic records from deep ice cores. Basal melt rates are affected by geothermal flux, one of the least constrained properties of the Antarctic continent. Estimates of Antarctic geothermal flux are typically regional in nature, derived from geological, magnetic or seismic data, or from sparse point measurements at ice core sites. We analyse ice-penetrating radar data upstream of South Pole revealing a ~100 km long and 50 km wide area where internal ice sheet layers converge with the bed. Ice sheet modelling shows that this englacial layer configuration requires basal melting of up to 6 ± 1 mm a and a geothermal flux of 120 ± 20 mW m, more than double the values expected for this cratonic sector of East Antarctica. We suggest high heat producing Precambrian basement rocks and hydrothermal circulation along a major fault system cause this anomaly. We conclude that local geothermal flux anomalies could be more widespread in East Antarctica. Assessing their influence on subglacial hydrology and ice sheet dynamics requires new detailed geophysical observations, especially in candidate areas for deep ice core drilling and at the onset of major ice streams.
南极冰盖底部的融化影响着冰动力学以及我们从深层冰芯中恢复古代气候记录的能力。底部融化速率受地热通量影响，而地热通量是南极大陆约束最少的特性之一。南极地热通量的估计通常是区域性的，源自地质、磁或地震数据，或来自冰芯站点的稀疏点测量。我们分析了南极点上游的探地雷达数据，发现一个长约100公里、宽50公里的区域，冰盖内部各层在此与冰床汇聚。冰盖模型显示，这种冰内冰层结构需要底部融化速率高达6±1毫米/年，地热通量为120±20毫瓦/平方米，这比东南极克拉通区预期值高出一倍多。我们认为，高放射性的前寒武纪基底岩石以及沿主要断层系统的热液循环导致了这种异常。我们得出结论，局部地热通量异常在东南极可能更为普遍。评估它们对冰下水文学和冰盖动力学的影响需要新的详细地球物理观测，特别是在深层冰芯钻探候选区域以及主要冰流的起始处。
