Science: This year, scientists reported alarming news about the huge continental ice sheet covering the western portion of Antarctica: It's headed for collapse, due to rapid melting of some of its buttressing ice shelves. When it does, global sea levels will rise by several meters. It has long been suspected that warm ocean waters at the base of those floating ice shelves are responsible for hurrying things along. But with scant data from the waters around Antarctica, that has been difficult to prove. Now,...