A new study by Eric Rignot, JPL, indicates that the Greenland ice sheet is losing ice at an increasing rate. Over the last decade, two thirds of this mass loss appears to be caused by acceleration of glaciers, an effect not accounted for in ice sheet models. Thus, these models underpredict the contribution of the Greenland ice sheet to future sea level.

Using satellite radar interferometry data Rignot and colleagues measured ice velocity around Greenland and deduced ice discharge by combining these data with ice thickness data. They find a mass loss caused by ice dynamics (accelerating outlet glaciers) increasing from 56 km³/yr in 1996 to 167 km³/yr in 2005. Two thirds of the mass loss
are caused by ice dynamics, vs one third by enhanced melt and precipitation. Hence, ice dynamics dominates the contribution of the ice sheet to sea level rise. As more glaciers accelerate farther north the mass deficit will continue to increase.
None of the physical processes involved with glacier acceleration in east Greenland in response to climate warming (enhanced basal lubrication, ungrounding of glacier fronts, ice-shelf removal, enhanced submarine melting at calving faces etc.) are included in models used to predict the future of the ice sheet. In effect these models underpredict what the contribution of Greenland to sea level might be in the future. (From abstract)

Session: CR11/G12 Observations of glaciers and ice sheets from space | >>programme