Greenland Albedo Variability

Recent results from the NASA funded Program for Arctic Regional Climate Assessment (PARCA) indicate that the margins of the Greenland ice sheet are thinning at a rapid rate. Thinning rates of more than 1m/yr are common along many of the outlet glaciers. Time-series from passive microwave have also shown that the areal extent of melt over the ice sheet been increasing since 1979. In 2002, the melt extent surpassed the maximum melt extent from the past 24 years by more than 9%. Because of these findings, increased attention is being paid to the ablation zones and coastal regions, with the emphasis on surface ablation and its sensitivity to summer warming and possible albedo feedback. This study examines the albedo variability in the ablation region and at some key outlet glaciers in Greenland. The AVHRR Polar Pathfinder albedo record is used to examine the long-term changes in the albedo from 1981 to 2000 at four outlet glaciers: Petermann, Jakobshavn, Storstrommen, and Kangerdlugssuaq. To study the 2002 summer melt anomaly, MISR and MODIS data are analyzed and used to retrieve the surface albedo. Validation of the MISR and MODIS-derived surface albedo are obtained through comparisons with in situ measurements in the Jakobshavn drainage basin. Analysis of the AVHRR albedo record at the glaciers reveals large seasonal and interannual variability in the surface albedo. Years with anomalously low surface albedo correspond to years in which the passive microwave record indicates anomalously high melt years. Analysis of the MODIS and MISR albedo during 2002 indicate that the melt began early in the Jakobshavn drainage basin and was extensive in that region as well as the northeast part of the ice sheet.