Biogeochemical responses to late-winter storms in the Sargasso Sea, III—Estimates of export production using 234Th:238U disequilibria and sediment traps
Author Posting. © Elsevier B.V., 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 56 (2009): 875-891, doi:10....
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ftwhoas:oai:darchive.mblwhoilibrary.org:1912/2901 2023-05-15T17:36:48+02:00 Biogeochemical responses to late-winter storms in the Sargasso Sea, III—Estimates of export production using 234Th:238U disequilibria and sediment traps Maiti, Kanchan Benitez-Nelson, Claudia R. Lomas, Michael W. Krause, Jeffrey W. 2009-01 application/pdf https://hdl.handle.net/1912/2901 en_US eng https://doi.org/10.1016/j.dsr.2009.01.008 https://hdl.handle.net/1912/2901 Episodic events Storms Particle Export Th-234:U-238 disequilibria Biogenic silica Organic carbon Preprint 2009 ftwhoas https://doi.org/10.1016/j.dsr.2009.01.008 2022-05-28T22:57:46Z Author Posting. © Elsevier B.V., 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 56 (2009): 875-891, doi:10.1016/j.dsr.2009.01.008. Direct measurements of new production and carbon export in the subtropical North Atlantic Ocean appear to be too low when compared to geochemical based estimates. It has been hypothesized that episodic inputs of new nutrients into surface water via the passage of mesoscale eddies or winter storms may resolve at least some of this discrepancy. Here, we investigated particulate organic carbon (POC), particulate organic nitrogen (PON), and biogenic silica (BSiO2) export using a combination of water column 234Th:238U disequilibria and free-floating sediment traps during and immediately following two weather systems encountered in February and March 2004. While these storms resulted in a 2-4 fold increase in mixed layer NO3 inventories, total chlorophyll a and an increase in diatom biomass, the systems was dominated by generally low 234Th:238U disequilibria, suggesting limited particle export. Several 234Th models were tested, with only those including non-steady state and vertical upwelling processes able to describe the observed 234Th activities. Although upwelling velocities were not measured directly in this study, the 234Th model suggests reasonable rates of 2.2 to 3.7 m d-1. Given the uncertainties associated with 234Th derived particle export rates and sediment traps, both were used to provide a range in sinking particle fluxes from the upper ocean during the study. 234Th particle fluxes were determined applying the more commonly used steady state, 1-dimensional model with element/234Th ratios measured in sediment traps. Export fluxes at 200 m ranged from 1.91 ± 0.20 to 4.92 ± 1.22 mmol C m-2 d-1, 0.25 ± 0.08 to 0.54 ± 0.09 mmol N m-2 d-1, and 0.22 ± 0.04 to 0.50 ± 0.06 mmol Si m-2 d-1. POC ... Report North Atlantic Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) Deep Sea Research Part I: Oceanographic Research Papers 56 6 875 891 |
institution |
Open Polar |
collection |
Woods Hole Scientific Community: WHOAS (Woods Hole Open Access Server) |
op_collection_id |
ftwhoas |
language |
English |
topic |
Episodic events Storms Particle Export Th-234:U-238 disequilibria Biogenic silica Organic carbon |
spellingShingle |
Episodic events Storms Particle Export Th-234:U-238 disequilibria Biogenic silica Organic carbon Maiti, Kanchan Benitez-Nelson, Claudia R. Lomas, Michael W. Krause, Jeffrey W. Biogeochemical responses to late-winter storms in the Sargasso Sea, III—Estimates of export production using 234Th:238U disequilibria and sediment traps |
topic_facet |
Episodic events Storms Particle Export Th-234:U-238 disequilibria Biogenic silica Organic carbon |
description |
Author Posting. © Elsevier B.V., 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 56 (2009): 875-891, doi:10.1016/j.dsr.2009.01.008. Direct measurements of new production and carbon export in the subtropical North Atlantic Ocean appear to be too low when compared to geochemical based estimates. It has been hypothesized that episodic inputs of new nutrients into surface water via the passage of mesoscale eddies or winter storms may resolve at least some of this discrepancy. Here, we investigated particulate organic carbon (POC), particulate organic nitrogen (PON), and biogenic silica (BSiO2) export using a combination of water column 234Th:238U disequilibria and free-floating sediment traps during and immediately following two weather systems encountered in February and March 2004. While these storms resulted in a 2-4 fold increase in mixed layer NO3 inventories, total chlorophyll a and an increase in diatom biomass, the systems was dominated by generally low 234Th:238U disequilibria, suggesting limited particle export. Several 234Th models were tested, with only those including non-steady state and vertical upwelling processes able to describe the observed 234Th activities. Although upwelling velocities were not measured directly in this study, the 234Th model suggests reasonable rates of 2.2 to 3.7 m d-1. Given the uncertainties associated with 234Th derived particle export rates and sediment traps, both were used to provide a range in sinking particle fluxes from the upper ocean during the study. 234Th particle fluxes were determined applying the more commonly used steady state, 1-dimensional model with element/234Th ratios measured in sediment traps. Export fluxes at 200 m ranged from 1.91 ± 0.20 to 4.92 ± 1.22 mmol C m-2 d-1, 0.25 ± 0.08 to 0.54 ± 0.09 mmol N m-2 d-1, and 0.22 ± 0.04 to 0.50 ± 0.06 mmol Si m-2 d-1. POC ... |
format |
Report |
author |
Maiti, Kanchan Benitez-Nelson, Claudia R. Lomas, Michael W. Krause, Jeffrey W. |
author_facet |
Maiti, Kanchan Benitez-Nelson, Claudia R. Lomas, Michael W. Krause, Jeffrey W. |
author_sort |
Maiti, Kanchan |
title |
Biogeochemical responses to late-winter storms in the Sargasso Sea, III—Estimates of export production using 234Th:238U disequilibria and sediment traps |
title_short |
Biogeochemical responses to late-winter storms in the Sargasso Sea, III—Estimates of export production using 234Th:238U disequilibria and sediment traps |
title_full |
Biogeochemical responses to late-winter storms in the Sargasso Sea, III—Estimates of export production using 234Th:238U disequilibria and sediment traps |
title_fullStr |
Biogeochemical responses to late-winter storms in the Sargasso Sea, III—Estimates of export production using 234Th:238U disequilibria and sediment traps |
title_full_unstemmed |
Biogeochemical responses to late-winter storms in the Sargasso Sea, III—Estimates of export production using 234Th:238U disequilibria and sediment traps |
title_sort |
biogeochemical responses to late-winter storms in the sargasso sea, iii—estimates of export production using 234th:238u disequilibria and sediment traps |
publishDate |
2009 |
url |
https://hdl.handle.net/1912/2901 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
https://doi.org/10.1016/j.dsr.2009.01.008 https://hdl.handle.net/1912/2901 |
op_doi |
https://doi.org/10.1016/j.dsr.2009.01.008 |
container_title |
Deep Sea Research Part I: Oceanographic Research Papers |
container_volume |
56 |
container_issue |
6 |
container_start_page |
875 |
op_container_end_page |
891 |
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1766136396847775744 |