Geomorphometric Characterization of Debris-covered Glaciers in the Karakoram Himalaya

Abstract:

Understanding climate-glacier dynamics in the Himalaya is notoriously difficult, as numerous forcing factors govern glacier mass balance and glacier sensitivity to climate change. There are large uncertainties associated with characterizing and predicting the spatio-temporal dynamics of debris-covered glacier surfaces due to topographic forcing, supraglacial debris sediment fluxes and depth, ablation rates and meltwater production, supraglacial lake development, and ice stress and velocity dynamics. Consequently, it is difficult to characterize glacier sensitivity to climate change and the degree to which glacier topography changes over time. Therefore, we examined the utility of geomorphometric parameters and objects to characterize temporal changes in glacier-surface topography that may be indicative of glacier sensitivity to climate change. Specifically, we utilized STRM and ASTER digital elevation models over the Karakoram Himalaya to evaluate some of the largest glaciers including the Baltoro, Batura, Biafo and Hispar Glaciers. We developed new geomorphometric parameters to characterize the first- and second-order topographic structures for these glaciers, and compared the spatial patterns over multiple years. Our results indicate that glacier-surface topographic patterns are spatially complex compared to the surrounding topography, and that spatial patterns vary significantly over time due to complex climate-glacier dynamics. Various patterns are associated with meltwater and ice flow, downwasting, supraglacial lakes, and the build-up of supraglacial debris. Quantitative characterization of these patterns can be used to map various process-form relationships over time. The presence of unique glacier morphologies and their rates of change may enable a first-order approximation of glacier sensitivity to climate change, as glacier-surface topography integrates feedback mechanisms that account for microclimate, ablation and meltwater production, and sediment transport and debris depth. We report on the utility of these metrics and patterns for characterizing and mapping glacier-surface morphodynamic conditions.