For the first time, Antarctic researchers have collaborated with elephant seals to record rates of sea-ice formation in the Southern Ocean. The Antarctic ocean, with its vast tracts of ice and climatically crucial ocean circulation patterns, is particularly vulnerable to warming. But lack of access to the ocean beneath the ice has hampered knowledge of the region.
Jean-Benoit Charrassin of the Natural History Museum, Paris, and colleagues attached temperature and salinity sensors to 58 southern elephant seals, which spend their winters feeding in the Antarctic sea-ice pack and surrounding waters. In total, the seals collected 16,500 depth profiles of the icy ocean during their daily dives in 2004–2005, a 30-fold improvement on other attempts to monitor sea ice. Using the salinity data, the researchers inferred seasonal changes in rates of sea-ice formation, which peaked in early winter. Combining seal data with satellite and buoy observations, they created a uniquely detailed map of ocean fronts — where different water masses meet — in seas south of 60° latitude.
Data collected by these and other seals will help fill a blind spot in scientists' understanding of the polar oceans — a prerequisite for gauging the region's response to, and role in, climate change.