9506596 Bilham The PIs will monitor the vertical motion of four tide gauge sites along the East Coast of the United States and Canada. They will also make absolute gravity surveys at the four tide gauge sites. Vertical tectonic motions observed with GPS and absolute gravity when combined with relative sea level measurements from the tide gauge will provide an accurate determination of the relative roles of crustal motion and absolute sea level rise in the region. The research will examine whether the vertical systematic errors in GPS and absolute gravity are sufficiently low at coastal sites to permit better than 3 mm agreement between the two systems. Long term averages given suitable corrections for the local effects suggest that they may agree to 1 mm. The proposed research aims to quantify their true agreement. ****
