CAREER: Understanding the Solid Earth's Influence on Sea Level

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Sea level lies at the intersection of Earth's solid, liquid, and gaseous components, and thus forms a fundamental boundary on our planet that affects both biology and geology. Human society must adjust to changes in this boundary, which is currently thought to be rising at 2-3 mm per year. Although it is known that climatological factors such as seawater warming and glacial melting are major contributors to sea level rise, deformation of the solid Earth also affects sea level in ways that are poorly constrained. This project uses numerical models of solid Earth deformation to understand the mechanisms by which the solid Earth influences sea level change over timescales ranging from decades to billions of years. By comparing predicted patterns of sea level change with observations, we will place new constraints on the solid Earth's effect on sea level. The scientific results from this effort will be translated directly into an educational program designed to teach undergraduate students about the interactions between the solid earth and sea level.This project will focus on three timescales relevant to modes of solid earth deformation. For timescales of decades to centuries, we will compute spatial variations in rates of sea level rise associated with Earth's elastic response to regional melting of glacial ice. For timescales of millennia and longer, we will compute the Earth's time-dependent viscous response to deglaciation. For timescales of millions of years and longer, we will use numerical models of mantle convection to determine how exchange of water between the oceans and Earth's interior affects sea level both directly and indirectly by changing ocean basin properties such as mid-ocean ridge volume, ocean area, and average seafloor depth. For each timescale, we will calibrate the sea level response to specific imposed forcing. By comparing these predicted patterns of sea level change with observations (obtained from satellite, tide gauge, sedimentary, and geologic constraints), we will place constraints on the historical and geologic causes of sea level change. This understanding will be incorporated into education modules that will be used by undergraduate students (first at the University of Hawaii and later everywhere via a publicly-available website) to probe the interaction between the solid earth and sea level in an interactive way. This research will help quantify the causes of sea level change and its spatial variations during the past decade and century, and thus will help inform coastal planning for future sea level rise. It will also help us understand the solid Earth's influence on sea level change over thousands and millions of years, which will help scientists understand the geologic record of sea level change and its coupling to the dynamics of Earth's interior.