How ice shelf morphology controls basal melting
How ice shelf morphology controls basal melting
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DOI：
10.1029/2008jc005197
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发表时间：
2009-12-05
影响因子：
3.6
通讯作者：
Oppenheimer, Michael
中科院分区：
文献类型：
--
作者：
Little, Christopher M.;Gnanadesikan, Anand;Oppenheimer, Michael
冰架基底融化对气候的响应是海洋温度、环流和公海混合以及这种外部强迫与冰架下环流耦合的函数。由于坡度强烈影响冰架底部附近浮力驱动流的特性，因此冰架形态在将外部地下热源与冰连接起来方面起着至关重要的作用。在本文中，在广泛的海洋温度和冰架形状下，对局部和区域综合融化速率的坡度驱动动态控制进行了研究，重点是较小、较陡的冰架。 3D 数值海洋模型用于模拟五个理想冰架下方的环流，这些冰架受地下海洋温度范围为 -2.0 摄氏度到 1.5 摄氏度的影响。在冰架下混合层中，存在三种空间上不同的动态状态。热量夹带主要发生在冰架较深的部分；局部和区域综合融化速率对这个“起始”区域的坡度变化最为敏感。一些夹带的热量被平流向上输送并用于融化“维持”区域的冰；然而，“流出”区域的流收敛限制了冰架平坦部分的热损失。冰的热通量表现出（1）空间上不均匀的、对坡度的超线性依赖性，以及（2）形状和温度依赖性、内部控制的效率。由于通过混合层的热通量效率随着海洋温度的升高而降低，数值模拟偏离了简单的二次标度定律。
The response of ice shelf basal melting to climate is a function of ocean temperature, circulation, and mixing in the open ocean and the coupling of this external forcing to the sub-ice shelf circulation. Because slope strongly influences the properties of buoyancy-driven flow near the ice shelf base, ice shelf morphology plays a critical role in linking external, subsurface heat sources to the ice. In this paper, the slope-driven dynamic control of local and area-integrated melting rates is examined under a wide range of ocean temperatures and ice shelf shapes, with an emphasis on smaller, steeper ice shelves. A 3-D numerical ocean model is used to simulate the circulation underneath five idealized ice shelves, forced with subsurface ocean temperatures ranging from -2.0 degrees C to 1.5 degrees C. In the sub-ice shelf mixed layer, three spatially distinct dynamic regimes are present. Entrainment of heat occurs predominately under deeper sections of the ice shelf; local and area-integrated melting rates are most sensitive to changes in slope in this "initiation'' region. Some entrained heat is advected upslope and used to melt ice in the "maintenance'' region; however, flow convergence in the "outflow'' region limits heat loss in flatter portions of the ice shelf. Heat flux to the ice exhibits (1) a spatially nonuniform, superlinear dependence on slope and (2) a shape-and temperature-dependent, internally controlled efficiency. Because the efficiency of heat flux through the mixed layer decreases with increasing ocean temperature, numerical simulations diverge from a simple quadratic scaling law.