Lowell D. Stott

Summary Statement of Research Interests
My research seeks to understand what factors have influenced the behavior of Earth's climate system over time. This research entails the acquisition paleoclimate records of atmosphere and ocean properties spanning years to millennia. These records provide insight into Earth’s past climate variability. With well resolved records from the ocean and atmosphere it is then possible to conduct model experiments to test hypotheses that would account for the variability observed in the paleorecords. Stott’s students and post doctoral scientists are pursuing studies to test two scientific hypotheses. These are: Hypothesis 1) Reduced sea surface temperature gradient between the tropical and extra-tropical North Pacific increases atmospheric variance (storm track behavior) that affects the number of storm events that strike the west coast of the US (California) and thus, the amount of precipitation that falls over western North America during winter. This hypothesis, if validated would have important implications for water resource management in the future as the ocean continue to warm. This hypothesis is being tested using ensemble simulations from an atmospheric general circulation model that is forced with specific sea surface temperature anomaly patterns. Times in the Earth’s past when the North Pacific experienced anomalously warm temperatures, including the so-called Medieval Climate Anomaly Period (1000 to 1300 AD), the northeastern Pacific sea surface temperatures were anomalously warm. This was also a time of prolonged drought over the western US. The hypothesis would predict that this extended period of drought was the result of altered storm track behavior that resulted from the change in sea surface temperature gradient between the tropical and extratropical Northeast Pacific. We are investigating storm track variance by analyzing the stable isotope composition of individual tree rings from long-lived trees that grow in California. The stable isotope composition of cellulose extracted from tree rings is indicative of the source of moisture that falls across the western US. Hypothesis 2) Testing the hypothesis that the flux of geologic carbon into the ocean and atmosphere varied in response to deep ocean temperature that regulate the stability of geologic reservoirs of liquid and solid (hydrate) forms of hydrothermal CO2. This hypothesis predicts that as the oceans cool during cold periods (ice ages) geologic carbon in the form of CO2 accumulates within sediments that blanket active hydrothermal systems. The accumulation of CO2 is accomplished because in the oceans cold temperatures and high pressures cause pure CO2 released from active vent systems to liquefy and solidify. Recent discoveries have revealed reservoirs of liquid CO2 trapped within sediments beneath a layer of solid (hydrate) CO2 formed at the sediment/water interface. But, when the oceans warm as they have during warm periods (deglaciation and interglacials), the hydrate layer is destabilized and the liquid CO2 leaks from these sediment reservoirs into the oceans and then to the atmosphere. The release of this CO2 then amplifies the climate warming. To test this hypothesis we are conducting a suite of measurements on samples collected around active vent systems in order to characterize the geochemical fingerprints imparted to the sediments by the hydrothermal fluids. These geochemical fingerprints are then used to identify when the hydrothermal fluids were released in Earth’s past.