Overview: our over-arching objective is to characterize outlet glacier mass variability in greenland and to understand the physical controls that limit outlet glacier change. Approach: this…

The University of Texas at Austin (UT Austin) was awarded a $648,295.99 grant by the National Aeronautics and Space Administration (NASA) to characterize outlet glacier mass variability in Greenland and understand the physical controls limiting glacier change. The project aims to construct a remote sensing dataset that will expand the temporal record of outlet glacier elevations in Greenland and increase the spatial resolution, enabling analysis of glacier dynamic change through empirical, theoretical, and numerical techniques. This effort supports NASA's objective of reducing uncertainty in expected future sea level rise by improving understanding of the Greenland ice sheet's response to climate change. The grant does not have a set-aside designation, as it was awarded to the University of Texas System, a large public university system in Texas that frequently partners with federal agencies on research and development initiatives across diverse scientific and technical domains.

Overview: our over-arching objective is to characterize outlet glacier mass variability in greenland and to understand the physical controls that limit outlet glacier change. Approach: this objective will be accomplished through construction of a remote sensing dataset that will fill in and nearly double the temporal record of outlet glacier elevations in select regions (extending to∼75 years) and increase the spatial resolution significantly. These observations will then be used to examine the nature and evolution of glacier dynamic change through empirical, theoretical, and numerical techniques. First, we will use kinematic wave theory to determine the limits to upstream elevation change following grounding line perturbations, allowing US to identify glaciers that are most susceptible to far-reaching inland thinning. Second, we will test kinematic wave theory by applying known changes at glacier termini to model the temporal evolution of thinning using the ICE sheet system model (issm). Lastly, we will use issm to test various calving laws to reproduce the observed retreat rates, allowing US to better understand the calving mechanism and to identify the mass losses possible from the most susceptible glaciers identified in the kinematic wave analysis. Uniqueness: greenland s mass balance is partially modulated by the changing dynamics of marine-terminating outlet glaciers. Our project aims to take advantage of a rich, historical database of imagery for coastal greenland going back to the 1940S. By doing so, our project will result in the most complete, long-term record of glacier elevation change for greenland. Using this data set, we will determine the limits to sea-level rise contribution from some of the most rapidly changing locations around the greenland ICE sheet, as well as those that have the potential to change rapidly in the future. This will be done by querying our observational data set to understand the degree to which regional versus local controls mitigate glacier dynamic change. We will improve understanding of glacier response to terminus perturbations and calving processes, which is presently a major GAP in our understanding of ICE sheet change. Our remote sensing e∼orts will produce valuable, widely-disseminated data products including: 1) improved measurements of ICE surface topographic evolution; 2) improved tracking of glacier terminus positions through time and; 3) estimates of glacier susceptibility to terminus perturbations. Value to NASA: a major objective of ICE sheet and climate research is to understand the response of the ICE sheets to climate change driven by present-day and future increases in greenhouse gases. Of particular importance is reducing uncertainty in the amount of expected future sea-level rise. Understanding the spatial and temporal controls on greenland glacier response to climate change is thus of immediate importance. Our proposal responds to the NASA-cryosphere solicitation to use remote sensing data to validate and improve models of land-based ICE and their contributions to sea-level change. Further, identifying the glaciers that might pose the largest risk to sea-level rise is critical in order to focus limited scientific resources where they are most needed. Our work will enable more focused e∼orts to understand satellite-altimetry-derived estimates of elevation change in those areas deemed to be more susceptible to future changes