Subpolar ocean gyres (large systems of rotating ocean currents) in the Southern Hemisphere are found poleward of the Antarctic Circumpolar Current near the Weddell and Ross Sea. They play a key role in the global energy and water budgets. These gyres are crucial for the transport of heat around the planet, as well as the distribution of nutrients and marine species. Thus, the subpolar gyres are important in the mixing and transformation of water masses. In a recent study, Dr. Zhaomin Wang shows the response of the subpolar gyres to projected climate changes. Although, there are large uncertainties in the projections of the circulation in the Southern Ocean, one the most robust results is the consistent increase in the westerlies (prevailing winds in the middle latitudes between 30 and 60 degrees latitude), which leads to an increase in the cyclonic wind forcing and an increase of the westward flow near Antarctica, an overall strength in the gyres. The study highlights the implications of the westward flow increase for the mass balance of ice shelves and the stability of Antarctic sheets. An intensification of the flow could bring warmer oceanic currents beneath the ice shelves, and more cyclonic wind forcing could bring more heat upward from the deeper ocean, a possible cause for the freshening in the subpolar regions observed in the past decades.
Wang, Z. (2013), On the response of Southern Hemisphere subpolar gyres to climate change in coupled climate models, J. Geophys. Res. Oceans, 118, 1070–1086, doi:10.1002/jgrc.20111