Improved methods for recovery of water balance variations of alpine and polar regions using grace data from the gravity recovery and climate experiment (grace) have been important tools for…

This is a grant awarded by the National Aeronautics and Space Administration (NASA) Shared Services Center to the University of Washington (UW) for research on improved methods for recovery of water balance variations in alpine and polar regions using data from the Gravity Recovery and Climate Experiment (GRACE). The $551,521.38 grant, awarded on February 16, 2016, is for the development of new approaches to enhance the accuracy and resolution of GRACE signal recovery over polar and alpine regions. The research aims to simulate the full water balance of these regions at the highest possible spatial resolution using tailored models, and to integrate the hydrological models into the GRACE processing workflow to achieve optimum fit to the GRACE data. This work is intended to standardize the treatment of hydrological signal recovery from GRACE in polar and alpine regions. The grant does not have a set-aside designation.

Improved methods for recovery of water balance variations of alpine and polar regions using grace data from the gravity recovery and climate experiment (grace) have been important tools for assessing seasonal variability and long-term mass trends of alpine and polar (non-ICE sheet) regions. Most studies attribute the mass loss trends to mountain glaciers, yielding a total sea level contribution that comprises one third of the present-day signal. However, identification of the hydrological systems contributing to the seasonal mass variability has been a major challenge. Many alpine regions are comprised of a highly distributed mixture of land surface types (glaciers, terrestrial snowpacks, lakes and ground water reservoirs) that have similar seasonal periodicity, and that have short-term variations that are often aliased in monthly grace solutions. Most grace studies attempt to correct for individual system components using land surface hydrology models, but these are often poorly calibrated, have a coarse spatial resolution and are unable to simulate complex glacier processes. As a result, nearly all grace solutions for alpine regions have focused on recovering long-term change in mass, but have given limited attention to the sub-annual mass change signals. This is unfortunate given the rich temporal detail in grace datasets that could be used to inform water resource planning, assess the potential for hazards and validate ecosystem and hydrological modeling research. We propose to develop new approaches that will significantly enhance the accuracy and resolution of grace signal recovery over polar and alpine regions. We will simulate the full water balance of alpine regions at the highest possible spatial resolution using a suite of models tailored specifically for simulation of cryospheric changes. Rather than trying to partition a fully processed grace solution to reconstruct individual hydrological processes, we will develop independent hydrology models, integrate them into the grace processing workflow, and use the grace observations as an objective measure of model performance. Then, in partnership with various grace teams, we will conduct iterative solutions, adjusting our model parameters and input datasets to achieve optimum fit to the grace data. For example, we will generate spherical harmonics from our estimated water balances for direct comparison to global spherical harmonic solutions. For mascon-based solutions, we will formally incorporate our simulated water balances into the grace level-1B processing in partnership with the NASA goddard space flight center gravimetry team. Our goal is to work with the science team to build new protocols that will to standardize the treatment of hydrological signal recovery from grace in polar and alpine regions. Our work will build on our existing efforts in the gulf of alaska region where we have carried out extensive testing of water balance simulations over a wide range of spatial and temporal scales driven by a suite of gridded climate products. We will assimilate field data together with NASA icebridge and satellite datasets that measure surface elevation variations. After refining our methods for alaska we will apply our models to other regions such as high mountain asia, patagonia and the canadian arctic. We will also work to incorporate and compare our output with existing modeling efforts where they exist. Our project will produce high resolution maps of the water balance of alpine regions, constrained to grace observations, for use in a variety of earth science applications. Our work will directly address nasas objectives to better understand the processes of water transfer in the earth and climate system, and to predict the response of these processes to climate change. Our new methods can be used to enhance recovery and partitioning of hydrological signals for current and future grace missions.