| Summary: | Ph.D. Observations this century have revealed that the Greenland Ice Sheet (GrIS) is losing mass at an accelerating rate. The GrIS contains ~7.4 m of potential global sea level rise if completely melted. About half of the total mass loss (>100 Gt yr -1 ) from 2003-2009 resulted from ice dynamic processes, expressed by rapid outlet glacier thinning. Southeast Greenland contributed a significant portion (~50%) to the total mass loss during this time. The physical forcing mechanisms responsible for the observed acceleration and thinning are not fully understood. The synchronous retreat of several southeast outlet glaciers in 2003 and restabilization in 2005 suggest a common regional forcing. Proposed forcings include oceanic and atmospheric warming of the calving front, as well as glacier/fjord geometry. It is imperative to quantitatively investigate dynamic ice loss processes to improve ice sheet models and sea level rise predictions. Continued monitoring and complete observational coverage are necessary to quantify dynamic loss. This work extends the spatiotemporal record of dynamic elevation changes at fast-flowing Helheim Glacier, which drains 3% of the GrIS. The novel Surface Elevation Reconstruction and Change detection (SERAC) approach utilizes laser altimetry time series to improve the vertical accuracy of existing Digital Elevation Model (DEM) datasets. The improved elevation record includes MicMacASTER (MMASTER) DEMs. This is the first study to combine MMASTER products with the SERAC procedure, yielding highly-accurate DEMs (<7 m vertical error) suitable for numerical modeling treatments.
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