Ocean circulation beneath the Ronne ice shelf

Abstract

THE intimate thermal contact between the base of Antarctic ice shelves and the underlying ocean enables changes in climate to have a rapid impact on the outflow of ice from the interior of Antarctica^1,2. Furthermore, water modified by passage under ice shelves, particularly in the Weddell Sea, is believed to be an important constituent of Antarctic Bottom Water³—a water mass that can be observed as far north as 50° N in the deep oceans⁴. Antarctic Bottom Water is both cold and oxygen-rich, and plays an important part in the cooling and ventilation of the world's oceans. Because of the difficulty in gaining access, the oceano-graphic regime beneath ice shelves is very poorly sampled⁵. By successfully drilling through the ice, however, we were able to obtain oceanographic data from beneath the largest Antarctic ice shelf, the Ronne–Filchner ice shelf in the southern Weddell Sea. We find that our data agree well with the predictions of a relatively simple oceanographic plume model of sub-ice-shelf circulation⁶. This model can therefore be used with some confidence to investigate the links between climate changes, ice-shelf melting and bottom-water production.