Assessing the influence of sea ice conditions on outlet glacier retreat in Disko and Uummannaq Bays, West Greenland

Monday, 15 December 2014
Ashley York1, Karen E Frey1, Sarah B Das2, Matthew Jared Evans3, Alex S Gardner4, Benjamin Eaton Smith5 and Luke D Trusel1,6, (1)Clark University, Graduate School of Geography, Worcester, MA, United States, (2)WHOI, Woods Hole, MA, United States, (3)Wheaton College, Norton, MA, United States, (4)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (5)University of Washington, Seattle, WA, United States, (6)Woods Hole Oceanographic Institution, Geology and Geophysics, Woods Hole, MA, United States
The variability in outlet glacier termini positions is an important indicator of overall glacier health and the net effects of ice-ocean-atmosphere interactions. Glacier margins fluctuate on both seasonal and interannual time scales, and owing to logistical difficulties associated with field observations, satellite imagery provides a critical spatially- and temporally-extensive resource for monitoring glacier behavior. In general, outlet glacier termini have been retreating globally over recent decades, but the magnitude of seasonal variation and overall retreat has proven unique to each glacier. The outlet glaciers in central West Greenland are generally experiencing the same regional atmospheric forcing, yet previous studies have shown varying magnitudes of retreat over the last forty years. Such observations point to the importance of local-scale forcing on outlet glacier dynamics. In this study, we utilized Landsat imagery between the years 1985 and 2014 to digitize a time series of glacier front positions of 18 outlet glaciers in the Disko and Uummannaq Bay regions of West Greenland. We additionally examined glacier terminus dynamics in context with proximal sea ice conditions (using SMMR, SSM/I and AMSR-E passive microwave-based sea ice concentrations) to assess the potential influence of ice mélange on terminus behavior. High-resolution WorldView satellite-based digital elevation models provide ancillary data that allow for investigation of the influence of ice mélange thickness on outlet glacier behavior across the region. Our findings suggest that the magnitude of seasonal variation in terminus position can be indicative of longer-term trends in glacier behavior. Furthermore, our results indicate that that duration of sea ice cover acts as a limiting force on the ability of a glacier to accelerate until the clearing of its mélange-filled fjord. These findings underscore the importance of glacier and fjord geometries in modulating glacier retreat across West Greenland.