Sensitivity of Antarctic Precipitation to Sea Ice Concentrations in a General Circulation Model

Several recent studies have highlighted the connections among observed climate variability, such as the Southern Oscillation, sea ice cover, and Antarctic precipitation. The direct contribution of observed sea ice variability to precipitation has not yet been investigated. The sensitivity of Antarctic precipitation to a range of sea ice concentrations is investigated using the Community Climate Model version 3 (CCM3) general circulation model. Sea ice concentrations derived from passive-microwave satellite imagery from 1979 to 1991 are used as surface boundary conditions for climate simulations in a model that resolves both ice-covered and ice-free fractions of each grid cell. Simulations are performed with climatological average ice concentrations, maximum and minimum concentrations, and an ensemble of simulations with interannually varying concentrations from 1979 to 1991. The minimum-ice run produces greater precipitation and onshore winds along the Antarctic coastal topography, except for the western Antarctic, where offshore winds reduce precipitation. The interannually varying model runs exhibit a seasonal response consistent with this picture, as greater precipitation is associated with reduced ice concentrations. The satellite-derived ice concentrations used here (and the model simulations) exhibit significant differences between the periods of coverage from the two satellite instruments with different spatial resolutions and other characteristics. The results suggest that variability in sea ice concentrations does contribute to variability in Antarctic precipitation; however, the modeled precipitation has a greater response to the instrument-related differences than to the estimated ice variability.