Oceanographic Observations at the Amundsen Sea Shelf Break

The continental shelf environment of the Amundsen and Bellingshausen seas differs markedly from that of the other circumpolar seas, where water temperatures are close to the surface freezing point throughout. In the Amundsen/Bellingshausen sector near-freezing temperatures are encountered only in the upper few hundred metres of the water column. Below this surface layer a broad thermocline trends towards upper Circumpolar Deep Water (uCDW), which is found in a form that is almost unmodified from its off-shelf manifestation (Giulivi and Jacobs, 1996). This means that the ice shelves of the Amundsen and Bellingshausen seas experience ocean temperatures some three degrees warmer than those experienced by the other Antarctic ice shelves, and the rates of basal melting are correspondingly high (Jacobs et al., 1996).