| Summary: | Our analysis of tree ring and sediment core data indicates that climate variability in the 1900s had different consequences in the Potomac Estuary and Chesapeake Bay than in the previous two centuries as a result of anthropogenic activity affecting nutrient loadings in associated watersheds. We associate variability in a 100-year time-series of the Southern Oscillation Index, and the North Atlantic Oscillation (NAO) index with the Palmer Drought Severity Index (PDSI) in the Potomac and Susquehanna watersheds. We relate a 300-year time- series of regional NAO and PDSI reconstructions, based on tree rings, to surrogate responses for eutrophication in a sediment core from mid Chesapeake Bay. Preliminary results suggest little relationship between variability in regional precipitation and a proxy for bottom-water dissolved oxygen in mid Chesapeake during the 1700-1800s. As a consequence of anthropogenic eutrophication closer coupling occurred during the 1900s. Since the late 1800s, there is a weak century-long trend toward wetter regional conditions. A transient application of the Hadley general circulation model predicts a continuation of this trend through the next century. Global anthropogenic activity may alter regional climate, making it more difficult to reduce nitrogen flux and restore coastal ecosystems in the Potomac Estuary and Chesapeake Bay.
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