A 2000-year record of temperature and salinity variation in Chesapeake Bay

Paleoclimatic records for the past 2000 years, including the Medieval Warm Period and Little Ice Age, were reconstructed from Marion-Dufresne cores from Chesapeake Bay (eastern North America). Mg/Ca ratios from the ostracode, Loxoconcha, and oxygen isotopes from the benthic foraminfer, Elphidium, are used as proxies of spring temperature and salinity, respectively. In the bay, salinity is directly related to Susquehanna River discharge, itself a function of regional rainfall. Chronology was constrained using radiocarbon dates derived from the mollusk, Mulinia lateralis, and historical pollen records of colonial land clearance. Mg/Ca ratios range from ~12 to 41 mmol/mol resulting in a temperature range of ~4 to 23° C. δ18 O values ranged from ~2.84 to +0.20‰ (VPDB) with a mean value of -1.16‰. Fluctuations in both the Mg/Ca and δ18O records confirm multidecadal climate variability during the Medieval Warm Period and Little Ice Age. These patterns are similar to those seen during 20th century NAO events, suggesting long term NAO climatic forcing for the region. The 20th century temperature and NAO-variability will be discussed in the context the last 2000 years of North Atlantic-wide climate variability.