The Greenland ice sheet, the planets second largest ice mass, has most recently been in a state of negative mass balance, contributing to about 15% of global sea level rise between 1991 and 2000 (Box et al, 2004). Results from NASA's Airborne Topographic Mapper (ATM) show an increase in the rate of Greenland's ice loss from 50 to 90 km /yr in the past 11 years (Krabill et al., 2004) corresponding to a global sea level rise of .25 mm/year since 1997. Debate exists as to whether or not this loss is caused by recent increases in temperature, or by dynamic processes.
Here, I use airborne laser altimetry to observe both long and short-term surface elevation values to calculate rates of changes over various time intervals. I then analyze regional climate data in an attempt to find a relationship between climate flux and glacier dynamics. Modeled Era 40 data (Bromwich et al., 2002) provide 6-hourly, 125 km resolution precipitation and temperature data from 1957 to 2002. Annual Angmassalik temperature station data from 1895 to 2004 is provided by the global historical climate network (GHCN). Higher resolution (24 km) temperature data is available from 1988 to 2004 (Box et al., 2004). Accumulation, surface mass balance and freshwater discharge data (24 km resolution) is available from 1991 to 2000.
Precipitation and temperature data was processed relative to four elevation-latitude bands, ablation was estimated from Era 40 data, and all Box data was processed
according to corresponding lidar flight path time intervals. Short-term thinning rates increase from .64 m/yr (between 1933 and 1981), while long term rates increased by .94 m/yr (between 1981 and 2001). Recent increases in temperature are seen in the 1990's and early 21st century. Positive degree-day sums increase through time and while ablation rates are minimal, they also increase through time. However, long-term temperature trends at the coastal station appear cyclic through time, suggesting recent climate flux is expected. Estimated ablation rates do not account for thinning rates previously calculated. Therefore, recent increases in thinning rates are not entirely driven by recent temperature changes, but must be driven by internal forcings as well.