Ice-shelf basal channels in a coupled ice/ocean model
Ice-shelf basal channels in a coupled ice/ocean model
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DOI：
10.3189/2012jog12j003
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发表时间：
2012-01-01
影响因子：
3.4
通讯作者：
Price, Stephen F.
中科院分区：
文献类型：
--
作者：
Gladish, Carl V.;Holland, David M.;Price, Stephen F.
提出了一个冰架与海洋相互作用的数值模式，其中冰架底部呈现出与Petermann Gletscher(格陵兰)漂浮冰架下观测到的相似的沟道化形态。通道是由接地线沿线冰层的不规则性引发的，然后因海洋融化而扩大。根据第一个近似值，接地线向海的空间可变的基础融化起到钢尺模具或模板的作用，在冰基经过时赋予其沟道化的形式。高熔体区域的海洋环流沿航道方向是惯性的，横向是地旋平衡的。融化速度取决于进入冰架的冰层厚度变化的波长，较短的波长会减少整体融化。因此，彼得曼·格列舍尔狭窄的底部通道可能起到保护冰架免受过度融化的作用。随着地下水变暖，模型中的整体融化增加。同样的敏感性也适用于非常轻微的降温，但对于零点几度的降温，融化空间格局的重组令人惊讶地导致距离接地线12公里的冰架灾难性变薄。沿着接地线的冰下淡水排放增加了整体融化。在冰的瞬变历史中，最终的稳态取决于何时开始放电，这表明耦合系统一般存在多个稳态。
A numerical model for an interacting ice shelf and ocean is presented in which the ice-shelf base exhibits a channelized morphology similar to that observed beneath Petermann Gletscher's (Greenland) floating ice shelf. Channels are initiated by irregularities in the ice along the grounding line and then enlarged by ocean melting. To a first approximation, spatially variable basal melting seaward of the grounding line acts as a steel-rule die or a stencil, imparting a channelized form to the ice base as it passes by. Ocean circulation in the region of high melt is inertial in the along-channel direction and geostrophically balanced in the transverse direction. Melt rates depend on the wavelength of imposed variations in ice thickness where it enters the shelf, with shorter wavelengths reducing overall melting. Petermann Gletscher's narrow basal channels may therefore act to preserve the ice shelf against excessive melting. Overall melting in the model increases for a warming of the subsurface water. The same sensitivity holds for very slight cooling, but for cooling of a few tenths of a degree a reorganization of the spatial pattern of melting leads, surprisingly, to catastrophic thinning of the ice shelf 12 km from the grounding line. Subglacial discharge of fresh water along the grounding line increases overall melting. The eventual steady state depends on when discharge is initiated in the transient history of the ice, showing that multiple steady states of the coupled system exist in general.