Abstract:
We reconstructed paleoclimate patterns from oxygen and carbon isotope records
from the fossil estuarine benthic foraminifera Elphidium and Mg/Ca ratios from
the ostracode Loxoconcha from sediment cores from Chesapeake Bay to examine
the Holocene evolution of North Atlantic Oscillation (NAO)-type climate
variability. Precipitation-driven river discharge and regional temperature
variability are
... the primary influences on Chesapeake Bay salinity and water
temperature, respectively. We first calibrated modern d18Owater to salinity
and applied this relationship to calculate trends in paleosalinity from the
d18Oforam, correcting for changes in water temperature estimated from ostracode
Mg/Ca ratios. The results indicate a much drier early Holocene in which mean
paleosalinity was ~28 ppt in the northern bay, falling ~25% to ~20 ppt during
the late Holocene. Early Holocene Mg/Ca-derived temperatures varied in a
relatively narrow range of 13C to 16C with a mean temperature of 14.2C and
excursions above 16C; the late Holocene was on average cooler (mean temperature
of 12.8C). In addition to the large contrast between early and late Holocene
regional climate conditions, multidecadal (20-40 years) salinity and
temperature variability is an inherent part of the region's climate during
both the early and late Holocene, including the Medieval Warm Period and Little
Ice Age. These patterns are similar to those observed during the twentieth
century caused by NAO-related processes. Comparison of the midlatitude
Chesapeake Bay salinity record with tropical climate records of Intertropical
Convergence Zone fluctuations inferred from the Cariaco Basin titanium record
suggests an anticorrelation between precipitation in the two regions at both
millennial and centennial timescales. 
