Satellite Remote Sensing of Arctic Glacier-Climate Interactions
As of 2002, Degree of Master of Science (MS) Quaternary and Climate Studies published under the auspices of the Climate Change Institute.
Abstract
The Arctic is an important part of the global climate system and glaciers there have the potential to caused a significant sea level rise. How three separate parts of this vast region are responding to a changing climate is the subject of this dissertation. The approach is to use satellite remote sensing to extract quantitative information over large spatial distances and long time periods. Mass balance studies of Svalbard's glaciers have, for the most part, been confined to small glaciers in western and southwestern Spitsbergen, where climate conditions are not representative of the whole archipelago. Here we investigate nine glaciers of varying size, median elevation, and aspect scattered throughout the archipelago. Archival aerial photographs, modern satellite imagery, and elevation data are used to map the areal changes at the termini and surface elevation changes from the 1960s through 2005. Smaller glaciers with lower median elevations have experienced the largest loss of area regardless of their geographical location. Two of the three northernmost glaciers have shown the smallest retreats while the third has consistently advanced since the 1990. Our findings highlight the need for caution when generalizing about the mass balance conditions of Svalbard based on changes on small glaciers which, while large in number, account for only ~34% of total glacier area of the archipelago. The presence of surface meltwater on ice caps and ice sheets is an important glaciological and climatological characteristic. We develop an algorithm for estimating the depth and hence volume of surface melt ponds using multispectral ASTER satellite imagery. The method relies on reasonable assumptions about the albedo of the bottom surface of the ponds and the optical attenuation characteristics of the ponded meltwater. We apply the technique to sequences of satellite imagery acquired over the western margin of the Greenland Ice Sheet to derive changes in melt pond extent and volume during the period 2003-2004. Results show large intra- and interannual changes in ponded water volumes, and large volumes of liquid water stored in extensive slush zones. Between 1970 and 1984, ground surveys were carried out along a flowline extending from the top of the south dome of Barnes Ice Cap to the margin. Over this period, the ice cap thinned an average of 1.7 m, or 0.12 m a-1. By comparing the 1984 survey with elevations derived from satellite imagery in 2006 we find that it has now thinned an additional 16.8 ± 7.7 m, or an average of ~0.76 ± 0.35 m a-1. A correlation between mass balance and mean summer temperature at nearby weather stations, developed over the period of the ground surveys, permits independent estimates of the thinning rate. These estimates are in excellent agreement with those based on satellite imagery. The acceleration in thinning is consistent with meteorological records documenting an increase in the number of positive degree days (atmospheric warming) in this region of the Canadian Arctic.