McGrath, Daniel听1听;听Steffen, Konrad听2听;听Overeem, Irina听3
1听颁滨搁贰厂
2听颁滨搁贰厂
3听滨狈厂罢础础搁
In situ measurements to quantify run-off from the Greenland Ice Sheet (GrIS) are hindered by logistical difficulties associated with the large, remote and spatially diverse nature of the ice sheet. Modeling studies suggest that run-off accounts for approximately 30-50% of the annual mass loss from the ice sheet, however, there is a need to more accurately quantify run-off with empirical measurements. The purpose of this research is to determine if remote sensing can be used to characterize the onset, duration and intensity of run-off. The primary field site includes a 6,280 km2 basin of the ice sheet, which runs off into the Watson River before flowing into Sondre Stromfjord, the longest fjord in west Greenland. The onset and duration of runoff into Sondre Stromfjord was compiled from Band 1 (620-670 nm, 250 m resolution) of the MODerate-resolution Imaging Spectroradiometer (MODIS) from 2001-2008. This study demonstrates that over this 8 yr period the plume formation occurred, on average, 10 days earlier. The onset of the plume is intrinsically related to the onset of ablation, supported by a positive correlation (r2=0.88) between the formation of the plume and the onset of ablation at the S5 (490 m asl, 6 km from ice margin) Kangerlussuaq Transect automatic weather station (2003-2008) (Figure 1). There is a similar positive correlation (r2=0.93) between the cessation of ablation and the settling of the plume. Sediment plume length variability throughout the 2007 and 2008 melt seasons is strongly correlated (r2=0.83) with an average Watson River discharge (Figure 2). This relationship is applied to plume length variability derived from MODIS imagery to reconstruct cumulative Watson River discharge from 2001-2008 (Figure 3). Reconstructed discharge compares favorably to measured cumulative discharge in 2007 and 2008.