Christian Science Monitor: The ice sheet sitting atop Antarctica is so vast, up to 3 miles (5 km) thick in some places, that it pushes earth’s crust thousands of feet down. If all that ice melted, it would raise sea levels globally by an estimated 230 feet (70 meters). No one thinks that Antarctica will thaw completely anytime soon, of course, but scientists are increasingly worried by changes observed in just one area: the West Antarctic Ice Sheet (WAIS). Until recently, scientists estimated that if the …