A 2-DIMENSIONAL MODEL FOR THE THERMOHALINE CIRCULATION UNDER AN ICE SHELF
A 2-DIMENSIONAL MODEL FOR THE THERMOHALINE CIRCULATION UNDER AN ICE SHELF
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DOI：
10.1017/s0954102089000490
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发表时间：
1989-12-01
影响因子：
1.6
通讯作者：
OLBERS, DJ
中科院分区：
文献类型：
--
作者：
HELLMER, HH;OLBERS, DJ
南极底水的产生受冰架水的影响，而冰架水是由巨大冰架下的陆架水团变质而形成的。采用垂直于冰架边缘的二维温盐环流模型，研究了入流条件、冰架底部热盐过程和冰架下层环流的耦合关系。考虑了适合菲奇纳冰架状态的不同边界条件。模型结果表明，一般情况下，冰架水向接地线输送，在接地线处，冰架底部的最大融化速率为1.5 μ m−1。冰的积累发生在靠近冰架边缘的融化区末端，速率约为0.1 μ m−1。这一堆积带的位置决定了由于盐的排空而引起的密度增加是否会导致上层环流单元和在中程深度处改变后的水团与冰架底部分离。在冰架边缘，模拟温度最低层的温度、盐度、氦和δ18O值是典型的冰架水。然而，亚冰架环流是高度可变的，并且对边界条件的变化非常敏感。流入水的特性或海底地形的适度变化可使环流强度加倍。堆积带的非线性过程引起的变化可以用影响整个环流的冰架边缘振荡器来描述。
The production of Antarctic Bottom Water is influenced by Ice Shelf Water which is formed due to the modification of shelf water masses under huge ice shelves. The coupling of inflow conditions, thermohaline processes at the ice shelf base and the sub-ice shelf circulation is studied with a two-dimensional thermohaline circulation model which has been developed for a section perpendicular to the ice shelf edge. Different boundary conditions appropriate to the Filchner Ice Shelf regime are considered. The model results indicate that, in general, shelf water is transported toward the grounding line, where at the ice shelf base melting occurs with a maximum rate of 1.5 my−1. Accumulation of ice takes place at the end of the melting zone close to the ice shelf edge with a rate on the order of 0.1 my−1. The location of this accumulation zone determines whether or not the density increase by salt rejection causes an upper circulation cell and the separation of the modified water mass from the ice shelf base at mid-range depth. At the ice shelf edge the simulated temperature, salinity, helium and δ18O values for the temperature minimum layer are typical for Ice Shelf Water. However the sub-ice shelf circulation is highly variable as well as sensitive to changes in boundary conditions. Moderate changes in the characteristics of the inflowing water or in sea-floor topography may double the intensity of the circulation. Non-linear processes in the accumulation zone cause variabilities which can be described by an ice shelf edge oscillator influencing the entire circulation regime.