Under this award the PIs will perform an integrated data-modeling study of Holocene oceanographic changes along the NE Pacific margin to understand the impact of Holocene climatic and oceanographic changes on marine and terrestrial communities (including human populations) along the NE Pacific Margin. The paleoenvironmental data will come from oxygen isotope, minor element, and 14C analyses of dated mollusk shells from archaeological sites in central California and British Columbia. Most of these shells have already been individually dated via 14C analysis as part of a project supported by NSF Geology & Paleontology. By coupling these three biogeochemical tracers, and examining both bulk samples (which integrate several years of growth) and intraskeletal growth series (which provide weekly-to-monthly temporal resolution), the PIs can reconstruct millennial, inter-annual, and seasonal variability in ocean temperature, upwelling intensity, and freshwater flux to the coastal zone. Through studies of extant mollusks, the PIs will develop species-specific isotope and minor element calibrations and assess the levels of variance inherent to nearshore species. To place the data in broader context, the PIs will use globaland regional-scale coupled atmosphere-ocean models to study the impact of changes in climate forcing on ocean currents, surface temperature, upwelling, and precipitation on a variety of time scales. Comparison of model results with proxy data will permit model performance, and may reveal key gaps in the proxy record. In addition to gaining insight into the factors driving climatic and oceanographic change along the NE Pacific margin, the PIs will use our climate data to test hypotheses for Holocene anthropological and paleoecological transitions.
