Measurement and Modeling of Cryosphere-Geosphere Interactions in South Central Alaska

Abstract:

In south central Alaska large cryosphere fluctuations occur on a variety of temporal and spatial scales in a region of upper crustal faulting and folding associated with collision and accretion of the Yakutat terrane. Over the last decade (2002-present) the Gravity Recovery and Climate Experiment (GRACE) gravity measurements from southern Alaska indicate region-specific trends of annual mass loss and large variable seasonal mass fluctuations. Unraveling the various geophysical signals within GRACE and continuous GPS data, as well as earlier campaign GPS data, has required acquiring geodetic constraints on changes in the cryosphere from satellite, aircraft, and in situ data. At broad spatial scales, short-term atmospheric loading corrections are important as well. On a more local scale, we use snow accumulation profiles from Larson’s GPS reflectometry, SNOTEL sites, and MODIS derived melt onset/refreeze timing to estimate the magnitude and timing of seasonal cryosphere loading and unloading. The regional GRACE trends need to be corrected for the rheological response to century time-scale ice mass loss as well. Our numerical modeling of the solid Earth response to cryosphere changes and earthquakes includes use of simple elastic models, regional finite element modeling with PyLith and a global normal model approach. For instance, our calculations predict the region specific GRACE trends due to ongoing mass change associated with viscoelastic relaxation following the 1964 and other earthquakes.