CORRELATION BETWEEN SEDIMENTARY BLACK CARBON ABUNDANCE AT A COASTAL NORTH CAROLINA SITE AND REGIONAL DROUGHT

Wildfires, which play an important role in the global carbon cycle, may increase in the future as a result of impending global warming. While typically thought to contribute carbon dioxide (CO₂) to the atmosphere on short time scales, wildfires also lead to carbon sequestration and eventual CO₂ burial by formation of refractory pyrogenic black carbon. One recent study suggests that such pyrogenic black carbon formation and carbon sequestration in Chesapeake Bay sediments during the Holocene were driven by cycles of drought which were specifically related to historical oscillations of the Intertropical Convergence Zone (ITCZ). In this study, we are testing the hypothesis that ITCZ migration throughout the Holocene may have also affected cycles of drought in coastal North Carolina. Specifically, we hypothesize that relatively greater abundances of sedimentary black carbon are coeval with periods of greater fires which occurred during drier climatic intervals. Furthermore, we hypothesize that these fires may have been modulated by migrations of the ITCZ. In order to test our hypotheses, we will present black carbon burial flux data from a sediment core from a coastal marsh in North Carolina. The age-depth model for this core is currently being developed using ²¹⁰Pb, ¹³⁷Cs and natural abundances of ¹⁴C. Sedimentary black carbon, also currently being extracted, involves demineralization using HCl-HF and then oxidation of non-black carbon organic carbon using potassium dichromate-sulfuric acid. The residual carbon is operationally defined as black carbon. Levels of black carbon in our core will be related to the regional Palmer Drought Severity Index as well as the Cariaco Basin titanium record. Testing our hypothesis will help determine if climate exerted a first order effect on carbon sequestration via black carbon formation in regional North Carolina as well as the Mid-Atlantic states.