POST EUROPEAN SETTLEMENT BLACK CARBON BURIAL AND CARBON SEQUESTRATION IN A CHESAPEAKE BAY SEDIMENT CORE

There is a critical need to more closely understand the relationship of drought on wildfire occurrence and carbon sequestration. Because pyrolysis of organic matter transforms biomass into refractory black carbon, drought-induced fires may represent a negative climate feedback, highlighting the role of pyrolysis as a means of carbon sequestration in the sedimentary record. Here, we present a high resolution record of post European settlement sedimentary black carbon abundance and composition in a Chesapeake Bay sediment core and compare this record with regional climate variability. A pronounced negative (-3 per mille) shift in stable isotopic signature of black carbon in our sediment core was observed in the early 1950s, suggesting increased reliance on fossil fuels began throughout the watershed after that time. Despite this anthropogenic “footprint” in the sedimentary record, periods of increasing relative abundance of black carbon from 1700 AD onwards are coeval with drier climatic intervals, as indicated by the Palmer Drought Severity Index (PDSI). This latter observation suggests that coastal carbon sequestration via black carbon formation in the Chesapeake Bay watershed may have been largely driven by regional climate. These findings have important implications for the global carbon cycle, as well as fire management in the face of future climatic predictions.