Postdoctoral Scholar: William Thompson
I’m concerned about future changes in the Earth’s climate and their potential human impact, and convinced that the geologic record holds important clues about the global climate system. I’m interested in Quaternary climate variability at a wide range of frequencies, from Milankovitch cycles to millennial and centennial timescales. My approach has focused on sea level, which is an integrated measure of the amount of ice on the continents. Global ice volume is both a sensitive index of global climate and an important boundary condition for paleoclimate modeling. While my early work in New England salt marshes examined possible sea-level responses to the Medieval Warm Period and Little Ice Age, I have more recently been investigating the details of sea-level change during the Last Interglacial, using the ages and elevations of fossil coral reefs. I am particularly interested in the timing of sea-level events during glacial terminations, and intrigued by the possibility of substantial sea-level oscillations occurring on sub-Milankovitch time scales. Because any time series is only as good as its dating, I have a fundamental interest in the theory and application of both radiocarbon and U/Th geochronology, as well as high-precision mass spectrometry. I’ve developed a novel approach to U-series dating that corrects ages for the commonly observed open-system behavior of U and Th nuclides in corals. New decay equations, derived from first principals, account for the alpha-recoil redistribution of uranium daughters during decay. These equations offer an attractive alternative to conventional equations for calculating U-series ages of corals, improving accuracy and dramatically increasing the available number of reliable ages. For the first time, it is possible to determine large numbers of accurate ages from a single terrace outcrop, resolving distinct millennial-scale sea-level events during previous interglacial periods.