Aquatic Sciences Meeting, Albuquerque 2001
| PC03 Undergraduate Education |
| Date: Tuesday, February 13, 2001 |
| Location: Southwest Hall |
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| Szlosek, J, E, University of Rhode Island Graduate School of Oceanography REU, Narragansett, USA, jenni1@mit.edu |
| Weinstein, S, E, University of Rhode Island Graduate School of Oceanography, Narragansett, USA, |
| Kelley, R, P, University of Rhode Island Graduate School of Oceanography, Narragansett, USA, |
| Edmonds, H, N, University of Texas at Austin Marine Science Institute, Port Aransas, USA, |
| Nelson, R, , Bedford Institute of Oceanography, Dartmouth, Canada, |
| Harrison, G, , Bedford Institute of Oceanography, Dartmouth, Canada, |
| Smith, J, N, Bedford Institute of Oceanography, Dartmouth, USA, |
| Burd, A, B, Texas A&M University Department of Oceanography, College Station, USA, |
| Moran, S, B, University of Rhode Island Graduate School of Oceanography, Narragansett, USA, |
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| SIZE-FRACTIONATED POC/234TH RATIOS IN THE UPPER LABRADOR SEA: IMPLICATIONS FOR 234TH-DERIVED POC EXPORT FLUXES |
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| Measurements of 234Th/238U disequilibrium and the particulate organic carbon (POC)/234Th ratio in the upper ocean are used to estimate the downward flux of POC from the euphotic zone. Developing a quantitative understanding of the variability in POC/234Th ratios of marine particles is essential for validating the use of 234Th to estimate POC fluxes from the surface ocean. Here we report water column measurements of POC/234Th ratios in three particle size-classes (1-10um, 10-53um, and >53um) from four stations in the Labrador Sea, July, 1999. Samples were collected using large-volume in-situ pumps and Go-Flo bottles. Results indicate (1) 234Th/238U disequilibrium at all locations, and (2) a decrease in the POC/234Th ratio with increasing particle size and, for the larger-size fractions, with depth. The latter is consistent with simulations derived using a physical adsorption-aggregation model. 234Th-derived POC export fluxes for the larger particle size-fractions are similar in magnitude, on the order of 3.2-32mmol C/m2/d2. The implication is that intermediate size particles (10-53um) contribute significantly to the total POC flux, which would have been underestimated using only the large particle (>53um) POC/234Th ratio. |
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