Pulse-drainage-induced surface acceleration near Jakobshavn Isbrae: water availability from supraglacial lakes

Water availability at the bed of the Greenalnd Ice Sheet influences sliding behavior. Recent results indicate that the most important factor affecting sliding rates is likely the variability of water input, rather than the total volume. Supraglacial lake drainage events have the capability to introduce large volumes to water to the bed of the ice sheet quickly, and are thus important in understanding the link between water input and ice acceleration. Here, we present a rapid-drainage chronology of supraglacial lakes in the Sermeq Avangnardleq catchment, west Greenland, for the 2010 and 2011 melt seasons. We derive the volumes of individual drainage events from ASTER, ETM+, and MODIS images using radiative transfer-based methodology similar to that developed by Sneed and Hamilton (2007). The method utilizes the gradual attenuation of red light with depth in water to estimate water level on a pixel-by-pixel basis and yields consistent volume estimates among disparate image types, providing the opportunity for greater temporal resolution and more accurate determination of drainage event timing. We explore the iceshed-scale availability and distribution of surface water as well as the relationships between the magnitude and timing of pulse-drainage events and surface velocity at several GPS stations within the catchment in an effort to better understand how interactions between the surface and subglacial environments influence outlet glacier dynamics on the Greenland Ice Sheet.