Rapid thinning of parts of the southern Greenland ice sheet

Aircraft laser-altimeter surveys over southern Greenland in 1993 and 1998 s how three areas of thickening by more than 10 centimeters per year in the s outhern part of the region and large areas of thinning, particularly in the east. Above 2000 meters elevation the ice sheet is in balance but thinning predominates at lower elevations, with rates exceeding 1 meter per year on east coast outlet glaciers. These high thinning rates occur at different l atitudes and at elevations up to 1500 meters, which suggests that they are caused by increased rates of creep thinning rather than by excessive meltin g. Taken as a whole, the surveyed region is in negative balance.