Estimating geoid height change in North America: past, present and future |
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Authors: | Thomas Jacob John Wahr Richard Gross Sean Swenson Geruo A |
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Institution: | 1. Department of Physics and Cooperative Institute for Environmental Studies, University of Colorado, Boulder, CO, USA 4. Bureau de Recherches Géologiques et Minières, Orléans, France 2. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA 3. National Center for Atmospheric Research, Boulder, CO, USA
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Abstract: | The forthcoming GRAV-D gravimetric geoid model over the United States is to be updated regularly to account for changes in
geoid height. Its baseline precision is to be at the 10–20 mm level over non-mountainous regions. The aim of this study is
to provide an estimate of the magnitude, time scale, and spatial footprint of geoid height change over North America, from
mass redistribution processes of hydrologic, cryospheric and solid Earth nature. Geoid height changes from continental water
storage changes over the past 50 years and predicted over the next century are evaluated and are highly dependent on the used
model. Groundwater depletion from anthropogenic pumping in regional scale aquifers may lead to geoid changes of 10 mm magnitude
every 50–100 years. The GRACE time varying gravity fields are used to (i) assess the errors in a glacial isostatic adjustment
model, which, if used to correct the GRAV-D model, may induce errors at the 10 mm geoid height level after ~20 years, (ii),
evaluate geoid height change over ice mass loss regions of North America, which, if they remain unchanged in the future, may
lead to geoid height changes at the 10 mm level in under a decade and (iii), compute sea level rise and its effect on the
geoid, which is found to be negligible. Coseismic gravitational changes from past North American earthquakes are evaluated,
and lead to geoid change at the 10-mm level for only the largest thrust earthquakes. Finally, geoid change from volcanic processes
are assessed and found to be significant with respect to the GRAV-D geoid model baseline precision for cataclysmic events,
such as that of the 1980 Mt. St. Helens eruption. Recommendations on how to best monitor geoid change in the future are given. |
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