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| Project Title | Investigating Hydrologic Loading in Southeast Alaska using GRACE and GPS Data |
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| Funding Agency | National Science Foundation (Grant EAR - Geophysics, NSF 06-546) |
| Principal Investigator | Jeffrey Freymueller |
| co-Investigators | Anthony Arendt |
| Collaborators | Satoshi Miura, Scott Luthcke |
| Duration | 2009-2012 |
Project Description
The magnitude and speed of its cryospheric changes make southeast Alaska the best place in the world to study ongoing glacial isostatic adjustment (GIA). Coastal glaciers and icefields of Southeast Alaska, British Columbia and Yukon Territory are shedding mass at a dramatic rate due to climate warming and the dynamics of tidewater glacier retreat. Deglaciation of this region began with the end of the Little Ice Age, and continues today, raising sea level and producing dramatic uplift and gravity change. Today’s spectacular Glacier Bay was created by the rapid tidewater retreat of glaciers beginning around 1800; glaciers originally well over 1 km thick in places disappeared in a few decades, with their ice discharged into the ocean. Continuous GPS observations show that post-glacial uplift does not occur at a steady rate; the ground subsides slightly throughout the winter before uplifting rapidly from the onset of the spring melt until subsidence begins again the next winter. The seasonal variations in height reach as much as 40-50 mm peak-to-peak. Data from the GRACE mission reveal corresponding seasonal variations in gravity. These variations are dominated by hydrological loading, and outside of the equatorial rain forest basins, nowhere on the planet features such extreme variations. The seasonal variations here were surprising, and larger than predicted by pre-GRACE hydrologic models. The large variations and the availability of precise geodetic data from the region lead us to pose several questions:
• Do the large seasonal variations in GPS height time series in southeast Alaska result from surface load variations? Can we explain these variations using a hydrological model constrained by GRACE observations?
• Can we develop an improved hydrologic model by combining GPS, GRACE and information on snow accumulation and melt, glacier extents and topography?
• Has the rate of mass change in the region has been constant over the last 15 years, or have mass loss rates have increased as the climate has continued to warm?
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