Thermal structure of proglacial lakes in Patagonia
Thermal structure of proglacial lakes in Patagonia
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DOI：
10.1002/2016jf004084
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发表时间：
2016-12
期刊：
影响因子：
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通讯作者：
S. Sugiyama;M. Minowa;D. Sakakibara;P. Skvarca;T. Sawagaki;Yoshihiko Ohashi;Nozomu Naito;K. Chikita
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文献类型：
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作者：
S. Sugiyama;M. Minowa;D. Sakakibara;P. Skvarca;T. Sawagaki;Yoshihiko Ohashi;Nozomu Naito;K. Chikita
在冰川前缘冰水相互作用的影响下，许多地区的崩解冰川正在迅速消退。与对潮水冰川前的峡湾进行的大量研究相比，对淡水崩解冰川终止的湖泊的研究却很少。为了更好地了解淡水崩解冰川前部的冰水相互作用，我们测量了佩里托莫雷诺冰川、乌普萨拉冰川和别德马冰川（南巴塔哥尼亚冰原的大型崩解冰川）附近的湖水温度、浊度和水深。这些湖泊的热结构与冰川峡湾中报道的热结构显着不同。没有迹象表明冰下融水有上升；相反，浑浊而寒冷的冰川水充满了湖底附近的区域。这是因为水密度是由悬浮沉积物浓度而不是水温控制的。近地表风驱动环流达到~180 m的深度，形成相对温暖的等温层（佩里托莫雷诺平均温度~5-6°C，乌普萨拉~3~4°C，别德马~6~7°C），这应该将热能输送到冰水界面。然而，冰川前缘的较深部分与分层的冷水接触，这意味着那里的融化量有限。在别德马冰川前面的湖中，深度超过 120 m 的区域完全充满了浑浊且非常寒冷的压力融化温度的水。我们的研究结果揭示了巴塔哥尼亚前冰湖的热结构，这表明它在淡水崩解冰川水下融化中的重要性。
Calving glaciers are rapidly retreating in many regions under the influence of ice‐water interactions at the glacier front. In contrast to the numerous researches conducted on fjords in front of tidewater glaciers, very few studies have been reported on lakes in which freshwater calving glaciers terminate. To better understand ice‐water interactions at the front of freshwater calving glaciers, we measured lakewater temperature, turbidity, and bathymetry near Glaciar Perito Moreno, Upsala, and Viedma, large calving glaciers of the Southern Patagonia Icefield. The thermal structures of these lakes were significantly different from those reported in glacial fjords. There was no indication of upwelling subglacial meltwater; instead, turbid and cold glacial water discharge filled the region near the lake bottom. This was because water density was controlled by suspended sediment concentrations rather than by water temperature. Near‐surface wind‐driven circulation reaches a depth of ~180 m, forming a relatively warm isothermal layer (mean temperature of ~5–6°C at Perito Moreno, ~3–4°C at Upsala, and ~6–7°C at Viedma), which should convey heat energy to the ice‐water interface. However, the deeper part of the glacier front is in contact with stratified cold water, implying a limited amount of melting there. In the lake in front of Glaciar Viedma, the region deeper than 120 m was filled entirely with turbid and very cold water at pressure melting temperature. Our results revealed a previously unexplored thermal structure of proglacial lakes in Patagonia, suggesting its importance in the subaqueous melting of freshwater calving glaciers.