Estimation of Ice Shelf Melt Rate in the Presence of a Thermohaline Staircase
Estimation of Ice Shelf Melt Rate in the Presence of a Thermohaline Staircase
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DOI：
10.1175/jpo-d-14-0106.1
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发表时间：
2015-01-01
影响因子：
3.5
通讯作者：
Venables, Emily
中科院分区：
文献类型：
--
作者：
Kimura, Satoshi;Nicholls, Keith W.;Venables, Emily
在南极洲乔治六世冰架正下方观测到有利于对流的扩散温盐阶梯。温盐阶梯是双扩散对流最明显的表现之一。冰的融化使海洋冷却和变新鲜，在温暖的咸水上方产生凉爽的淡水，这种水团分布有利于一种称为扩散对流的双扩散对流。虽然水团的垂直分布容易受到扩散对流的影响，但迄今为止，在冰架下面的观测都没有显示出这一过程的信号，而且它对冰架融化的影响是不确定的。通常使用基于三方程模型的参数化来估计冰架的融化速度，该模型假设在水力光滑表面上存在充分发展的无分层湍流。在温盐楼梯的存在下，这些先决条件显然不满足。基础融化速率是通过应用现有的扩散对流热通量参数化，结合对乔治六世冰架下一个地点海洋条件的测量来估计的。这些估算得出的融化速率可能在0.1至1.3 m yr（-1）之间，其中该地点观测到的融化速率与1.4 m yr(1)相似。讨论了冰架下扩散对流公式的局限性及其意义。
Diffusive convection-favorable thermohaline staircases are observed directly beneath George VI Ice Shelf, Antarctica. A thermohaline staircase is one of the most pronounced manifestations of double-diffusive convection. Cooling and freshening of the ocean by melting ice produces cool, freshwater above the warmer, saltier water, the water mass distribution favorable to a type of double-diffusive convection known as diffusive convection. While the vertical distribution of water masses can be susceptible to diffusive convection, none of the observations beneath ice shelves so far have shown signals of this process and its effect on melting ice shelves is uncertain. The melt rate of ice shelves is commonly estimated using a parameterization based on a three-equation model, which assumes a fully developed, unstratified turbulent flow over hydraulically smooth surfaces. These prerequisites are clearly not met in the presence of a thermohaline staircase. The basal melt rate is estimated by applying an existing heat flux parameterization for diffusive convection in conjunction with the measurements of oceanic conditions at one site beneath George VI Ice Shelf. These estimates yield a possible range of melt rates between 0.1 and 1.3 m yr(-1), where the observed melt rate of this site is similar to 1.4 m yr (1). Limitations of the formulation and implications of diffusive convection beneath ice shelves are discussed.