Applying the UK37 Method in the Chesapeake Bay: Calibration, Development, and Comparison With Paleotemperatures Obtained From Mg/Ca Ratios
Abstract
Unsaturated ketone ratios (UK37) have been successfully used as a paleotemperature proxy for open-ocean waters for the past 15 years. To extend this method to a near-shore environment, a new linear relationship has been established between UK37 values and temperature in the Chesapeake Bay (CB) estuary (salinity ranging from 9-18 \permil) from particulate matter filtered over the course of one year (Mercer et al., 2000). The CB equation (UK37 = 0.0311(T) - 0.0938, R2 = 0.8263) gives paleotemperatures ~5-6° warmer than those derived from the Prahl and Wakeham equation (1987). Here, we will report the second year's particulate data, which will be used to validate the newly derived equation. In addition, we will present further evidence of the validity of this method by comparing UK37 and Mg/Ca ratio SST values derived from the same depths using a long core (MD99-2209) drilled in the northern Chesapeake Bay. Preliminary results show the two methods give SST values within 2° of each other for recent sediments. Both methods give a temperature range of 11-28° since 500ybp and indicate a substantial cooling around the time of the Little Ice Age. This further calibration of the UK37 method and the comparison with the Mg/Ca ratio SST index demonstrate its potential as a near-shore paleotemperature proxy. Mercer, J.L., Zhao, M. and S.M. Colman (2000) Linear Relationship Between UK37 Values and Temperature in the Chesapeake Bay Water Column. American Geophysical Union Fall Conference, San Francisco. Prahl, F.G. and S.G. Wakeham (1987) Calibration of Unsaturation Patterns in Long-chain Ketone Compositions for Palaeotemperature Assessment. Nature 330, 367-369.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AGUFMPP32B0528M
- Keywords:
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- 1055 Organic geochemistry;
- 4235 Estuarine processes;
- 4267 Paleoceanography