If the ice sheet covering Greenland melted, global sea levels would rise 21 feet, profoundly impacting our planet. How, why, and when could this happen? A few years ago, scientists found lost sediment from a secret sub-ice Cold War base in the Arctic from the 1960s that holds clues to a time when Greenland Ice Sheet was gone. is an hour-long documentary about the discovery of this sediment and the critical implications of the science to our future. The finding that the ice sheet melted in the past completely transforms our understanding of the stability of the Greenland Ice Sheet.