Melting from below Scientists have long known that glaciers resting under sea level can be unstable if they rest on a downward sloping sea bed. I. Warmer ocean currents erode the glacier's base from below. The grounding line retreats downhill, and as it does, even more of the glacier is exposed to warm water. It melts more, and flows faster. Thinning Previous profile of ice sheet 04009FICS Receding Previous edge of ice shelf Ice front Grounding line Continental when ice flow shelf was stable Source: 'Contribution of Antarct.ca to Past and Future Sealevel Rise,' by Robert M. Der-onto and David Pollard, in Nature CHIQUI ESTEBAN, BONNIE BERKOWITZ, PATTERSON CLARK / THE WASHINGTON POST EFTA01190033