Emplacement of Antarctic ice sheet mass affects circumpolar ocean flow

Abstract

During the Cenozoic the Antarctic continent experienced large fluctuations in ice-sheet volume. We investigate the effects of Glacial Isostatic Adjustment (GIA) on Southern Ocean circulation for the first continental scale glaciation of Antarctica (~34Myr) by combining solid Earth and ocean dynamic modeling. A newly compiled global early Oligocene topography is used to run a solid Earth model forced by a growing Antarctic ice sheet. A regional Southern Ocean zonal isopycnal adiabatic ocean model is run under ice-free and fully glaciated (GIA) conditions. We find that GIA-induced deformations of the sea bottom on the order of 50m are large enough to affect the pressure and density variations driving the ocean flow around Antarctica. Throughout the Southern Ocean, frontal patterns are shifted several degrees, velocity changes are regionally more than 100%, and the zonal transport decreases in mean and variability. The model analysis suggests that GIA induced ocean flow variations alone could impact local nutrient variability, erosion and sedimentation rates, or ocean heat transport. These effects may be large enough to require consideration when interpreting the results of Southern Ocean sediment cores.