Nature: To better study Antarctic bottom water (AABW)—cold, salty water that forms near the shores of Antarctica—researchers recruited elephant seals that they outfitted with sensors. “The seals went to an area of the coastline that no ship was ever going to get to, particularly in the middle of winter,” said Guy Williams of the Antarctic Climate and Ecosystem Cooperative Research Centre in Hobart, Australia, and a coauthor of the study published yesterday in Nature Geoscience. Three sources of AABW had previously been identified. Thanks to the seals, a fourth was found: in the Cape Darnley polynya. A polynya is an area of open water surrounded by sea ice; winds and ocean currents keep the water from freezing, and it has a high saline content due to the expulsion of salt by sea-ice formation. Because the water is denser than typical ocean water, it sinks and then starts flowing north, creating deep-ocean currents of cold water. According to the researchers, the formation of AABW is a key process in global ocean circulation and can have important effects on Earth’s climate.