HR: 0800h
AN: PP51C-0614    [Abstracts]
TI: Organic Carbon and Bio-Barium Deposition in Eocene Equatorial Pacific Sediments: Does a 'Biological Thermostat' Maintain End-Member Climates?
AU: * Olivarez Lyle, A
EM: aml@cgiss.boisestate.edu
AF: CGISS, Boise State University, 1910 University Drive, Boise, ID 83725 United States
AU: Lyle, M
EM: aml@cgiss.boisestate.edu
AF: CGISS, Boise State University, 1910 University Drive, Boise, ID 83725 United States
AB: Results are presented from the first high-resolution, high quality, organic carbon mass accumulation rate (MAR) dataset of the Eocene equatorial Pacific upwelling region (Sites 1218 and 1219, Leg 199 of the Ocean Drilling Program.) Measured Corg fluxes are an order of magnitude lower than Holocene rates. In contrast, expected organic carbon MAR's and bio-barium fluxes, a proxy indicator of productivity, are roughly equal to modern rates. The discrepancy between the `expected vs. observed organic carbon sedimentation rates' begs the question of what happened to the `missing' sedimentary organic carbon? The answer is fundamental for understanding the geochemical carbon cycle because mass balance models assume that the organic carbon sub-cycle is balanced. Changes in the sedimentation patterns of calcium carbonate, diatoms, bio-barium, and organic carbon collectively suggest that temperature is the over-riding physical parameter that controls organic carbon deposition. Bottom water temperatures during the Eocene were 10 - 12 §C warmer than modern, as reported by Leg 199 scientists, and we draw from recent advances in ecology and biochemical kinetics to suggest that warm temperatures during the Eocene affected the ecological structure and nutrient cycle to produce a positive feedback of CO2 to the atmosphere. This mechanism, or `biological thermostat', effectively would have maintained the warm Eocene climate regime. The proposed mechanism is robust because CO2 feedbacks are predicted to be negative during colder climate regimes and observed sedimentation patterns in Leg 199 sediments are consistent with this scenario during a time of cooling during the Eocene. In other words, the `biological thermostat' also would act to maintain cold climates during `icehouse' conditions.
DE: 0428 Carbon cycling (4806)
DE: 1051 Sedimentary geochemistry
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 4999 General or miscellaneous
DE: 9355 Pacific Ocean
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005