Assessing supraglacial water volume and the changing dynamics of the surface topography near the Jakobshavn Glacier, Greenland.

摘要

On the Greenland Ice Sheet (GIS), the effect of the melt season's changing supraglacial lakes on outlet glacier discharge is not well understood. It is known that many supraglacial lakes drain rapidly during each melt season. While there are conflicting theories of the significance of supraglacial lake drainages towards enhancing ice sheet flow, it is highly important to quantify the actual water volume of supraglacial lakes since their drainage via crevasses or moulins enables the injection of melt water directly into the GIS.;The 2008 Arctic MUltiSensor Cryospheric Observation eXperiment (Arctic MUSCOX) was the first scientific Unmanned Aircraft System (UAS) used in Greenland. The goal was determination of the changing volumes of supraglacial melt water lakes through the fusion of disparate data sets from in-situ, airborne, and satellite sensors. Near the Jakobshavn Isbrae region, four supraglacial lakes at different elevations along a transect at 68.73°N were monitored over the 2006, 2007, and 2008 melt seasons. The changing lake volumes are calculated for each day of usable MODIS imagery, employing DEM's from both ASTER Global and the MUSCOX lidar survey. During this three year period, no observed lake was larger in volume than 0.15km3, or larger in area than 10.4km2, implying a size limit for supraglacial lakes.;In this study a new technique is developed calculating runoff using daily changing albedo and surface height measurements (dH) from the Greenland Climatic Network (GC-Net) Automatic Weather Stations (AWS) at locations JAR1 and JAR2. Runoff is calculated on a daily basis, both regionally and for a 1,183km 2 inset strip straddling the transect. At JAR1 the calculated linear runoff for 2006, 2007, and 2008 is 1.79m, 1.99m, and 1.96m, respectively; at JAR2 the calculated runoff is 2.11m, 2.86m, and 2.40m, respectively. Regional projections are made that account for future atmospheric temperature increases between 0.5°C and 3.0°C; they indicate up to a 43.3% increase in the area available for the formation of supraglacial lakes in the GIS.;Finally, a proposal is presented to obtain scientific measurements of Arctic Key Parameters (AKP's) in the region's data sparse areas via UAS through the cooperation of the international community.