Scientists say that part of a critical ice shelf in West Antarctica could break apart within the next five years. The ice shelf helps stabilize Thwaites Glacier and the entire West Antarctic Ice Sheet. And its fate has big implications for future sea level rise. A group of scientists midway through a five-year research project on Thwaites is reporting its findings at the American Geophysical Union conference this week. The World’s environment correspondent Carolyn Beeler reports.