Controls on the transport of oceanic heat to Kangerdlugssuaq Glacier, East Greenland
Controls on the transport of oceanic heat to Kangerdlugssuaq Glacier, East Greenland
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DOI：
10.1017/jog.2016.117
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发表时间：
2016-01-01
影响因子：
3.4
通讯作者：
Hanna, Edward
中科院分区：
文献类型：
--
作者：
Cowton, Tom;Sole, Andrew;Hanna, Edward
格陵兰岛以海洋为终点的冰川可能对海洋热量很敏感，但控制向冰川终点输送热量的峡湾过程仍然受到很少的限制。在这里，我们使用东格陵兰Kangerdlugssuaq峡湾的三维数值模式来检验对峡湾/陆架交换的控制。我们发现，陆架强迫的中间环流可以在10d内将多达25%的峡湾体积替换为陆架水域，而浮力驱动的环流(由海洋终止冰川的冰下径流强迫)在10d的时间内交换类似于典型夏季条件下峡湾体积的10%。然而，虽然中间循环在峡湾和陆架之间产生了更高的交换率，但浮力驱动的循环随着时间的推移是一致的，因此在沿着峡湾全长输送水时更有效。因此，我们发现浮力驱动的环流是融化季节海洋热量向冰川输送的主要途径。然而，除非有足够的冰下融化的淡水输入，否则中间环流将在冬季占据主导地位。我们的发现表明，陆架水温度的上升和浮力驱动的环流增强，导致康格尔鲁格斯苏亚克冰川可供融化的热量在1993-2001年至2002-11年间增加了约50%，与该冰川快速退缩的开始大致一致。
Greenland's marine-terminating glaciers may be sensitive to oceanic heat, but the fjord processes controlling delivery of this heat to glacier termini remain poorly constrained. Here we use a three-dimensional numerical model of Kangerdlugssuaq Fjord, East Greenland, to examine controls on fjord/shelf exchange. We find that shelf-forced intermediary circulation can replace up to similar to 25% of the fjord volume with shelf waters within 10 d, while buoyancy-driven circulation (forced by subglacial runoff from marine-terminating glaciers) exchanges similar to 10% of the fjord volume over a 10 d period under typical summer conditions. However, while the intermediary circulation generates higher exchange rates between the fjord and shelf, the buoyancy-driven circulation is consistent over time hence more efficient at transporting water along the full length of the fjord. We thus find that buoyancy-driven circulation is the primary conveyor of oceanic heat to glaciers during the melt season. Intermediary circulation will however dominate during winter unless there is sufficient input of fresh water from subglacial melting. Our findings suggest that increasing shelf water temperatures and stronger buoyancy-driven circulation caused the heat available for melting at Kangerdlugssuaq Glacier to increase by similar to 50% between 1993-2001 and 2002-11, broadly coincident with the onset of rapid retreat at this glacier.