Richard A. Kerr
SAN FRANCISCO--Oceanographers have had a hard time identifying where and how the oceans' deep, salty bottom waters mix with the overlying warmer layers. But a deep-diving instrument package has discovered a clue, researchers reported last month at the American Geophysical Union meeting here: a zone of intense mixing over a region of rugged ocean bottom off Brazil, 5600 meters down. By churning the overlying waters, regions of rough bottom may account for much of the oceans' missing mixing.