Recent ice sheet growth in the interior of Greenland

Recent growth in the interior regions of the Greenland Ice Sheet is reported by a Norwegian-led team of climate scientists. The growth is estimated to be about 6 cm per year during the study period, 1992–2003. They derive and analyse the longest continuous dataset of satellite altimeter observations of Greenland Ice Sheet elevations by combining tens of millions of data points from European Space Agency (ESA) satellites, called ERS-1 and ERS-2, and NASA. This allowed the scientists to determine the spatial patterns of surface elevation variations and changes over an 11-year period between 1992 and 2003.

The motivation for the study of the Greenland Ice Sheet is related to global climate change. First, complete melting of the ice sheet would raise the global sea level up to 7 meters. This process, expected to occur on a millennial time scale, should begin upon crossing the critical threshold for surface air temperature increase (~3ºC) for Greenland, which is predicted to happen before the end of this century. Second, increased Greenland Ice Sheet melt and freshwater input into the northern North Atlantic Ocean is theorized to weaken the Gulf Stream at high latitudes and possibly even disrupt the global thermohaline circulation on a relatively rapid, multi-decadal time scale. If this were to happen, it would severely impact the climate of northern Europe and even on a global scale.

Efforts to measure changes in the Greenland Ice Sheet from field observations, aircraft and satellite remote sensing – such as altimeters that measure surface height – have improved our knowledge over the past decade. However, there is still no consensus assessment of the overall mass balance of the ice sheet. There is however evidence of melting and thinning in the coastal marginal areas in recent years, as well as indications that large Greenland outlet glaciers can surge, possibly in response to climate.

However, much less known are changes that may occur in the vast elevated interior area of the ice sheet (Images 1 and 2). Previous studies by American scientists had reported a high-elevation ice-sheet balance. However, those assessments were based on a limited number of tracks of aerial altimetry, unevenly sampled in space and time, as well as short records from satellites.