Climatic variability in the eastern United States over the past millennium from Chesapeake Bay sediments

Abstract

anthropogenic perturbations to Earth's atmosphere, or a combination of factors (Rind and Overpeck, 1993). Because instrumental records rarely exceed 100 yr, paleoclimate reconstructions can establish which factors are most important over multidecadal time scales, distinguish anthropogenic and natural causes, and test climate-model simulations of decadal-and centennial-scale variability (Latif, 1998). Paleoclimatic records from polar and tropical regions suggest that decadal-and centennial-scale climate changes are characteristic of the past millennium, a period that includes the Medieval Warm Period (ninth through fourteenth centuries) and the Little Ice Age (fifteenth through nineteenth centuries) (Hughes and Diaz, 1994; Overpeck et al., 1997). Yet, except for tree-ring records (i.e., Cook and Jacoby, 1983; Stahle et al., 1998), multicentury records are sparse from most of the United States, and the ecological impacts of Holocene climate variability remain poorly known. We investigated the past millennium of paleoclimatic history of the mid-Atlantic region preserved in the sedimentary record of Chesapeake Bay. Chesapeake Bay, the largest estuary in the United States, is a 320-km-long, 20-40-kmwide, 6500 km 2 drowned river valley (average and maximum depths of 8.5 m and 53 m, respectively) inundated by the late Quaternary sea-level rise ca. 6-8 ka (Colman and Mixon, 1988). The bay's thick Holocene section (Colman and Halka, 1989) contains micropaleontological and geochemical evidence for changes in freshwater and sediment inflow, salinity, dissolved oxygen, and temperature (Cronin et al., 1999a). Its record of decadal-and centennial-scale variability holds promise for understanding impacts of past and climate change.

Major shifts in multidecadal moisture variability in the Mid‐Atlantic region during the last 240 years

“…Also, the d 18 O variations at White Lake are consistent with the paleosalinity reconstructed from Chesapeake Bay over the last ∼240 years [Cronin et al, 2000], with higher d 18 O values at White Lake corresponding to higher salinities at Chesapeake Bay (Figures 2b and 2c). Paleosalinity was reconstructed using a quantitative relationship between the salinity and relative abundance of the benthic foraminifer Elphidium [Cronin et al, 2000]. Changes in paleosalinity at Chesapeake Bay reflect changes in precipitation in the watershed and fresh-water discharge to the Bay [Cronin et al, 2000].…”

“…However, the available instrumental data for the Mid-Atlantic region are either incomplete or inconsistent with each other, making it difficult to further test these ideas for a longer time-frame. Extending the instrumental record to longer time periods requires high-resolution paleoclimate reconstructions, and surprisingly very few high-resolution paleoclimate records [e.g., Cronin et al, 2000] are available for the highly populated Mid-Atlantic region.…”

The response of Chesapeake Bay salinity to climate‐induced changes in streamflow

“…This exercise would be meaningful in the sense that all estuaries may be affected by climate change, particularly through river runoff changes (Miller and Russell 1992). Likewise, the modeling scheme developed here is easily adaptable for reverse calculations, such as reconstructing ancient watershed hydrology and climate using fossil proxies as salinity inputs (Cronin et al 2000).…”

Multidecadal Climate Variability and Drought in the United States

“…While most recent drought research has taken place in the western half of the United States (where extended drought is more likely due to high interannual variability in precipitation; Diaz 1983), a few investigators have studied multidecadal drought in the eastern United States. Cronin et al (2000Cronin et al ( , 2005, for example, found evidence of drought variability in Chesapeake Bay sediments over the past several millennia. More recently, they identified 14 dry/wet cycles since 1500 AD and found evidence of multidecadal droughts in the 16th and 17th centuries.…”