Greenland ice sheet melt extent: 1979-1999

Analysis of melt extent on the Greenland ice sheet is updated to span the time period 1979-1999 and examined along with its spatial and temporal variability using passive microwave satellite data. To acquire the full record, the issue of continuity between the previous passive microwave sensors (SMMR, SSM/I F-8, and SSM/I F-11) and the most recent SSM/I F-13 sensor is addressed. The F-13 cross-polarized gradient ratio melt-classification threshold is determined to be -0.0154. Results show that for the 21-year record, a positive melt trend of nearly 1 %/yr is observed, but this trend falls just below the 90% significance level. The observed melt increase does appear to be driven by conditions in the western portion of the ice sheet, rather than the east where melt appears to have decreased slightly. Moreover, the eruption of Mount Pinatubo in 1991 is likely to have had some impact on the melt but not so much as previously suspected. The 1992 melt anomaly is 1.7 standard deviations from the mean. Finally, the relationship between coastal temperatures and melt extent suggests an increase in surface runoff contribution to sea level of 0.31 mm/yr for a 1degreesC temperature rise.