EASTERN U.S. HOLOCENE CLIMATE VARIABILITY FROM CHESAPEAKE BAY SEDIMENTS

Chesapeake Bay, the largest estuary in North America, exhibits seasonal and inter-annual salinity variability controlled primarily by fluctuations in river discharge, which in turn are linked to regional precipitation. The oxygen isotopic composition of modern Chesapeake water (d¹⁸O_bay) is strongly correlated with salinity (r²=0.96), and varies based on the mixing of fresh and marine bay water. Reconstruction of temporal trends in d¹⁸O_bay were determined based on the d¹⁸O_calcite of the benthic foraminifer Elphidium, and Mg/Ca paleothermometry from paired specimens of the ostracode Loxoconcha to correct for temperature influence on d¹⁸O. Salinity reconstructions in mesohaline and polyhaline regions show a range of d¹⁸O_bay values from ~-0.5 to –3.5 per mil, which convert to paleosalinities from ~14 to > 30 ppt. Bay salinity and temperature exhibit multi-decadal and centennial variability, with large temperature excursions during the Little Ice Age (~1400-1900) and Medieval Warm Period (~800-1300) that may be indicative of North Atlantic circulation processes. Simple regression models used to estimate Susquehanna discharge and regional precipitation from salinity reconstructions suggest precipitation varied between 5 to >12 cm/month. Precipitation values show similar multi-decadal and centennial droughts and wet intervals, ~ 30% drier mean early Holocene conditions, and a wetter and more variable twentieth century that may indicate anomalous recent climate behavior.