HR: 0800h
AN: OS11B-0501    [Abstracts]
TI: Estimates of Export production in Sargasso Sea During Winter Storms Prior to Seasonal Stratification
AU: * Maiti, K
EM: kmaiti@geol.sc.edu
AF: Department of Geological Sciences, University of South Carolina, 701 Sumter Street EWSC617, Columbia, SC 29208, United States
AU: Benitez-Nelson, C R
EM: cbnelson@geol.sc.edu
AF: Department of Geological Sciences, University of South Carolina, 701 Sumter Street EWSC617, Columbia, SC 29208, United States
AU: Lomas, M W
EM: michael.lomas@bios.edu
AF: Bermuda Institute of Ocean Sciences, St. George's GE 01, St Georges, 01, Bermuda
AU: Krause, J W
EM: jkrause@coas.oregonstate.edu
AF: College of Ocean and Atmospheric Science, Oregon State University, Corvallis, Corvallis, OR 97331, United States
AB: Direct estimates of primary production in the subtropical North Atlantic Ocean appear to be too low when compared to geochemical based estimates of carbon export. It has been suggested that difficult to measure episodic inputs of new nutrients to surface waters by eddies or storms may solve this discrepancy. In this study, we investigated carbon export using ²³⁴Th:²³⁸U disequilibria and free-floating sediment traps during and immediately following two weather systems encountered in February and March 2004. These storms resulted in a 2-4 fold increase in mixed layer NO₃ inventories and a subsequent increase in autotrophic biomass. The average of ²³⁴Th based and trap based particulate organic carbon (POC) and biogenic silica (bSiO₂) fluxes at 200 m during this study period were 3.39 ± 1.39 mmol C m^-2 d^-1 and 0.36 ± 0.15 mmol Si m^-2 d^-1, respectively. While POC export was elevated by a factor of two relative to average winter estimates in this region, it still remains well within the range of non-storm winter fluxes observed in the region. The C export efficiency (export/primary production) was ~ 7%, similar to the ~ 4% observed under ambient conditions. Thus, while the passage of weather systems perturb the system by leading to increased productivity, autotrophic biomass (particularly diatoms), and export, they do not appear to increase the efficiency at which carbon is removed from the system by particle sinking. In contrast, the three fold increase in bSiO₂ fluxes observed during storms is significantly higher (p < 0.007) than that typically observed. This suggests that, given the vastness of the North Atlantic mid-ocean gyre, winter storms may significantly impact silica cycling in this region.
DE: 4273 Physical and biogeochemical interactions
DE: 4805 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4912)
DE: 4808 Chemical tracers
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting