Regional estimates of the export flux of particulate organic carbon derived from thorium-234 during the JGOFS EqPac program
- 31 December 1995
- journal article
- Published by Elsevier BV in Deep Sea Research Part II: Topical Studies in Oceanography
- Vol. 42 (2-3), 777-804
- https://doi.org/10.1016/0967-0645(95)00043-p
Abstract
The upper ocean 234Th activity distribution at 77 stations was measured between 12°N and 10°S, and 95°W and 170°W in the spring and autumn of 1992. A regional scavenging model was used to estimate vertical export of particulate 234Th. Given the relatively high upwelling rates in this region, particularly at equatorial latitudes near 140°W, it was necessary to include upwelling of 234Th in our model in order to quantify particulate export. Using this export flux and the measured organic C or N to 234Th ratio on particles, one can empirically determine POC and PON fluxes for this region. The estimated particulate organic C flux varies spatially and temporally within this region, ranging from 1 to 7 mmol C m−2 day−1, with enhanced export occurring over the equator. Fluxes are also enhanced along 95°W coincident with a low temperature/high nutrient peak at 4°S. Along 140°W, particulate organic C export from the upper 100 m is on the order of 2 mmol C m−2 day−1 at latitudes beyond 4°N and 4°S, with an equatorial peak of 3–5 mmol C m−2 day−1 in both spring and fall. These results suggest that a relatively small per cent of the total production is exported locally on sinking particles (particle export/primary production ratios. Given the measured ratio, particulate N fluxes from the upper 100 m would be 6 times lower than for POC.Keywords
This publication has 23 references indexed in Scilit:
- CO2 distributions in the equatorial Pacific during the 1991–1992 ENSO eventDeep Sea Research Part II: Topical Studies in Oceanography, 1995
- Export production of particles to the interior of the equatorial Pacific Ocean during the 1992 EqPac experimentDeep Sea Research Part II: Topical Studies in Oceanography, 1995
- Physical and Biological Controls on Carbon Cycling in the Equatorial PacificScience, 1994
- A three dimensional time‐dependent approach to calibrating sediment trap fluxesGlobal Biogeochemical Cycles, 1994
- Determination of transuranic and thorium isotopes in ocean water: In solution and in filterable particlesJournal of Radioanalytical and Nuclear Chemistry, 1987
- Oceanic stratified euphotic zone as elucidated by 234Th: 238U disequilibria1Limnology and Oceanography, 1987
- 238U,234U and232Th in seawaterEarth and Planetary Science Letters, 1986
- The removal rates of234Th and228Th from waters of the New York BightEarth and Planetary Science Letters, 1981
- Natural radionuclides in the water of Narragansett BayEarth and Planetary Science Letters, 1979
- 234Th/238U ratios in the oceanEarth and Planetary Science Letters, 1968