Collaborative Research: Water Isotope Model-Data Comparison for Holocene Climate Variability

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This project will use funds to develop a series of coupled isotope modeling experiments, data collection, and data model comparisons to provide new insights into Holocene climate change, with an emphasis on the hydrologic cycle. Science questions to be addressed include: 1) What was the response of the hydrologic cycle to insolation changes during the Holocene? 2) What was the isotopic signature in precipitation and ocean waters of these changes? 3) Did insolation-forced changes in the hydrological cycle influence deep or intermediate water production in the high latitudes? 4) Is the spatial signature of the climate response, including terrestrial water isotope and d18O of seawater (d18Osw) anomalies, associated with the 8.2 ka event consistent with input of freshwater into the Hudson Strait? 5) What are the combined effects of insolation changes and persistent, ENSO-like patterns on global climate, and are such changes observed in paleo-water isotope archives? and 6) What are the patterns associated with long-term intrinsic variations of the climate system (i.e. unforced decadal NAO or thermohaline variability)?To address these questions, coupled ocean-atmosphere global circulation model (AOGCM) simulations will be performed. These are to include appropriate insolation, residual land ice, and an 8,200-year experiment by adding freshwater as the base case for the control run. The effect of sustained El Nino-Southern Oscillation (ENSO) events and the cause of significant discrepancies between AOGCM and data will be explored with AGCM experiments. Transient behaviors of orbitally forced climate, including isotope records, are to be evaluated using one long coupled experiment employing accelerated orbital forcing.The work will also generate new data (Magnesium/Calcium-based sea surface temperature estimates and planktonic foraminifera oxygen isotopes) to be used in conjunction with water isotope records from ice cores, lakes, speleothems, and corals, and existing marine isotope seawater composition records to validate model output.Several graduate students at Columbia University and the Woods Hole Oceanographic Institute will be supported by this research and benefit by interacting with researchers at multiple institutions. All new data, data syntheses, and model simulations will be submitted to publicly funded web based data repositories.