Salt release during sea ice freezing produces dense water off Antarctica that sinks to the ocean abyss, reports a study published online in Nature Geoscience. The work suggests that this process is responsible for the formation up to 13% of the deepest ocean water mass, Antarctic Bottom Water.

Kay Ohshima and colleagues used oceanographic data from moorings and instrumented elephant seals to track down the source of an unattributed component of Antarctic Bottom Water. They found that the dense water is produced in a region of intense sea ice formation off Cape Darnley, at latitudes 65-69° E. Only three other locations of Antarctic Bottom Water formation were known previously, but unlike the Cape Darnley site, these locations feature ice shelves or a large shallow shelf where water can pool before it sinks.

In an accompanying News and Views, Michael Meredith states: “Ohshima et al. have identified a new mechanism for the generation of the densest water in the oceans”.