Effect of ocean temperature variations on the position of the lower boundary of an ice shelf

Ice ablation/accumulation on the lower surface of an ice shelf turns out to be dependent on the temperature of the ocean water inflowing under the ice shelf. The ice shelf seals off the ocean from short-term fluctuations in atmospheric temperature. For this reason, conditions under the ice shelf are unique for estimating temperature variations in the ocean water flowing into the shelf cavity. The goal of this work is to study the effect of ocean temperature variations on the position of the phase interface between the ice and ocean water. The ocean water inflowing under the ice shelf is localized in the lower portion of the shelf cavity, where the water is warmer and saltier than in the upper layers. Water inflow under the ice shelf is described using a two-dimensional model of thermohaline circulation. The feature of this model lies in the fact that it generates regions of water supercooled to a temperature lower than the equilibrium temperature for a given salinity. Thermodynamically, this state is unstable; for this reason, our model was extended to include underwater ice formation from supercooled water. This process is described by the equations of a multicomponent medium. Ocean temperature variation is specified by the boundary condition on the edge of the ice shelf. The parameters of the ice shelf are chosen in agreement with data obtained for the Filchner-Ronne Ice Shelf. It is stated that underwater ice formation slows down the outflow from the cavity (maximum velocity reduces from 12 to 9 cm/s). The maximum rate of ice upbuilding decreases from 8 to 4 cm/year. The maximum percentage of underwater ice measures 38%. Simulations have shown that, in principle, ice shelf monitoring can be implemented if the annual average temperature variation of the ocean water inflowing under the ice shelf △T measures about Ο 0.01°C/year. The deviation of the phase transition rate measures 2.5 cm/year for △T = 0.01°C/year and 1.5 cm/year for △T = -0.01°C/year.