LAUSR

In 2021, U.S. researchers will go to the frozen expanse of Greenland9s northern ice sheet to pinpoint the last time it disappeared. The 5-year, $7 million campaign, awarded last month by the National Science Foundation, will mark the first large U.S. ice drilling program in Greenland in more than 25 years. But unlike past projects, the target is not the climate records held in the ice, but the rocks underneath, which contain radioactive clocks that show when they were last exposed to air. Recent evidence has suggested much of the ice sheet disappeared during the past million years, when temperatures were similar to today9s. The project will hunt for signs of that retreat, while also searching for signs of melting ice on the sheets9 margins from a warm period 8000 years ago. It will also drill close to the controversial Hiawatha impact crater, potentially constraining the timing of the strike that formed it.