A two-dimensional model for the thermohaline circulation under an ice shelf

hhellmer [ at ] awi-bremerhaven.de


The production of Antarctic Bottom Water is influenced by Ice Shelf Water which is formed due tothe modification of shelf water masses under hughe ice shelves. The coupling of inflow conditions,thermohaline processes at the ice shelf base, and the sub-ice shelf circulation is studied with atwo-dimensional thermohaline circulation model which has been developed for a sectionperpendicular to the ice shelf edge. Different boundary conditions appropriate to the Filchner IceShelf regime are considered. The model results indicate that, in general, shelf water is transportedtoward the grounding line, where at the ice shelf base melting occurs with a maximum rate of1.5 m/a. Accumulation of ice takes place at the end of the melting zone close to the ice shelf edgewith a rate on the order of 0.1 m/a. The location of this accumulation zone determines whether ornot the density increase by salt rejection causes an upper circulation cell and the separation ofthe modified water mass from the ice shelf base at mid-range depth. At the ice shelf edge thesimulated temperature, salinity, helium, and delta18O values for the temperature minimum layerare typical for Ice Shelf Water. However, the sub-ice shelf circulation is highly variable as well assensitive to changes in boundary conditions. Moderate changes in the characteristics of theinflowing water or in sea-floor topography may double the intensity of the circulation. Non-linearprocesses in the accumulation zone cause variabilities which can be described by an ice shelfedge oscillator influencing the entire circulation regime.

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Hellmer, H. and Olbers, D. (1989): A two-dimensional model for the thermohaline circulation under an ice shelf , Antarctic Science, 1 (4), pp. 325-336 .

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