9706407 Nerem The objective of this investigation is to make Global Positioning System (GPS) measurements of 3-dimensional crustal deformation in the northeastern U.S., combined with absolute gravity and tide gauge measurements, to infer the viscosity of the lower mantle and thus improve current models of glacial isostatic adjustment. This will allow the PIs to determine the relative roles of crustal motion and sea level rise in this region, and also develop an improved estimate of global mean sea level rise from the global tide gauge data set. They will install 6 new permanent GPS sites along the northeastern coast of the U.S., which will supplement the current sites in the Continuously Operating Reference System (CORS), which will also be evaluated for use in this investigation. A related objective of the investigation is to develop improved methods of GPS vertical positioning, including modeling vertical motions associated with pressure loading, tidal loading, etc. The PIs anticipate this investigation will result in an improved understanding of sea level change in the northeastern U.S., an improved model of glacial isostatic adjustment, and an improved estimate of global sea level change through the application of this model to the global tide gauge data. ***
