Advection and scavenging: Effects on 230Th and 231Pa distribution off Southwest Africa
We investigated the controls of hydrography and of scavenging on the distribution of the particle reactive radionuclides 231Pa and 230Th in the water column and in surface sediments off Southwest Africa (Angola and Cape basins). Based on a vertical section of total 230Thex concentrations in the wate...
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Online Access: | https://oceanrep.geomar.de/id/eprint/9132/ https://oceanrep.geomar.de/id/eprint/9132/1/Advection.pdf https://doi.org/10.1016/j.epsl.2008.03.060 |
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ftoceanrep:oai:oceanrep.geomar.de:9132 2023-05-15T17:13:49+02:00 Advection and scavenging: Effects on 230Th and 231Pa distribution off Southwest Africa Scholten, Jan Fietzke, Jan Mangini, A. Garbe-Schönberg, C.-Dieter Eisenhauer, Anton Schneider, Ralph Stoffers, Peter 2008 text https://oceanrep.geomar.de/id/eprint/9132/ https://oceanrep.geomar.de/id/eprint/9132/1/Advection.pdf https://doi.org/10.1016/j.epsl.2008.03.060 en eng Elsevier https://oceanrep.geomar.de/id/eprint/9132/1/Advection.pdf Scholten, J., Fietzke, J. , Mangini, A., Garbe-Schönberg, C. D., Eisenhauer, A. , Schneider, R. and Stoffers, P. (2008) Advection and scavenging: Effects on 230Th and 231Pa distribution off Southwest Africa . Earth and Planetary Science Letters, 271 (1-4). pp. 159-169. DOI 10.1016/j.epsl.2008.03.060 <https://doi.org/10.1016/j.epsl.2008.03.060>. doi:10.1016/j.epsl.2008.03.060 info:eu-repo/semantics/restrictedAccess Article PeerReviewed 2008 ftoceanrep https://doi.org/10.1016/j.epsl.2008.03.060 2023-04-07T14:57:25Z We investigated the controls of hydrography and of scavenging on the distribution of the particle reactive radionuclides 231Pa and 230Th in the water column and in surface sediments off Southwest Africa (Angola and Cape basins). Based on a vertical section of total 230Thex concentrations in the water column we show that small differences in the salinity between the North Atlantic Deep Water (NADW) in the Angola Basin and the NADW in the Cape Basin as well as the advection of NADW associated with the Namib Col Current are reflected in total 230Thex concentrations. These variable total concentrations are believed to reflect the flow path and mixing history of NADW with the NADW in the Angola Basin being relatively older and 230Th enriched compared to the NADW in the Cape Basin. In the area investigated we found high 231Paex/230Thex ratios (231Paex/230Thex > 0.093) in surface sediments at the continental margin and lower ones (231Paex/230Thex < 0.093) in the open ocean. Such a distribution is normally interpreted to result from high particle flux at ocean margins (boundary scavenging). However, the lack of any significant depletion of dissolved 230Th and 231Pa in the water column does not indicate extensive scavenging at the continental margin. High 231Paex/230Thex ratios are constrained to shallow waters depths (< 2000 m) only and coincide with low fractionation between 231Pa and 230Th indicating that preferential scavenging of 231Pa on opal may have caused high 231Paex/230Thex ratios in the sediments. The observed close negative correlation (r2 = 0.82) between 231Paex/230Thex ratios in sediments and water depths is believed to reflect changes in the particle composition, i.e. a decrease in opal content with water depth. In the Angola and Cape basins the total 231Paex concentrations in NADW were the highest observed so far in the Atlantic Ocean, and they are attributed to the meridional export of 231Pa from the North Atlantic. This caused the average dissolved 231Pa/230Th in the Southeast Atlantic to be ... Article in Journal/Newspaper NADW North Atlantic Deep Water North Atlantic OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Earth and Planetary Science Letters 271 1-4 159 169 |
institution |
Open Polar |
collection |
OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
op_collection_id |
ftoceanrep |
language |
English |
description |
We investigated the controls of hydrography and of scavenging on the distribution of the particle reactive radionuclides 231Pa and 230Th in the water column and in surface sediments off Southwest Africa (Angola and Cape basins). Based on a vertical section of total 230Thex concentrations in the water column we show that small differences in the salinity between the North Atlantic Deep Water (NADW) in the Angola Basin and the NADW in the Cape Basin as well as the advection of NADW associated with the Namib Col Current are reflected in total 230Thex concentrations. These variable total concentrations are believed to reflect the flow path and mixing history of NADW with the NADW in the Angola Basin being relatively older and 230Th enriched compared to the NADW in the Cape Basin. In the area investigated we found high 231Paex/230Thex ratios (231Paex/230Thex > 0.093) in surface sediments at the continental margin and lower ones (231Paex/230Thex < 0.093) in the open ocean. Such a distribution is normally interpreted to result from high particle flux at ocean margins (boundary scavenging). However, the lack of any significant depletion of dissolved 230Th and 231Pa in the water column does not indicate extensive scavenging at the continental margin. High 231Paex/230Thex ratios are constrained to shallow waters depths (< 2000 m) only and coincide with low fractionation between 231Pa and 230Th indicating that preferential scavenging of 231Pa on opal may have caused high 231Paex/230Thex ratios in the sediments. The observed close negative correlation (r2 = 0.82) between 231Paex/230Thex ratios in sediments and water depths is believed to reflect changes in the particle composition, i.e. a decrease in opal content with water depth. In the Angola and Cape basins the total 231Paex concentrations in NADW were the highest observed so far in the Atlantic Ocean, and they are attributed to the meridional export of 231Pa from the North Atlantic. This caused the average dissolved 231Pa/230Th in the Southeast Atlantic to be ... |
format |
Article in Journal/Newspaper |
author |
Scholten, Jan Fietzke, Jan Mangini, A. Garbe-Schönberg, C.-Dieter Eisenhauer, Anton Schneider, Ralph Stoffers, Peter |
spellingShingle |
Scholten, Jan Fietzke, Jan Mangini, A. Garbe-Schönberg, C.-Dieter Eisenhauer, Anton Schneider, Ralph Stoffers, Peter Advection and scavenging: Effects on 230Th and 231Pa distribution off Southwest Africa |
author_facet |
Scholten, Jan Fietzke, Jan Mangini, A. Garbe-Schönberg, C.-Dieter Eisenhauer, Anton Schneider, Ralph Stoffers, Peter |
author_sort |
Scholten, Jan |
title |
Advection and scavenging: Effects on 230Th and 231Pa distribution off Southwest Africa |
title_short |
Advection and scavenging: Effects on 230Th and 231Pa distribution off Southwest Africa |
title_full |
Advection and scavenging: Effects on 230Th and 231Pa distribution off Southwest Africa |
title_fullStr |
Advection and scavenging: Effects on 230Th and 231Pa distribution off Southwest Africa |
title_full_unstemmed |
Advection and scavenging: Effects on 230Th and 231Pa distribution off Southwest Africa |
title_sort |
advection and scavenging: effects on 230th and 231pa distribution off southwest africa |
publisher |
Elsevier |
publishDate |
2008 |
url |
https://oceanrep.geomar.de/id/eprint/9132/ https://oceanrep.geomar.de/id/eprint/9132/1/Advection.pdf https://doi.org/10.1016/j.epsl.2008.03.060 |
genre |
NADW North Atlantic Deep Water North Atlantic |
genre_facet |
NADW North Atlantic Deep Water North Atlantic |
op_relation |
https://oceanrep.geomar.de/id/eprint/9132/1/Advection.pdf Scholten, J., Fietzke, J. , Mangini, A., Garbe-Schönberg, C. D., Eisenhauer, A. , Schneider, R. and Stoffers, P. (2008) Advection and scavenging: Effects on 230Th and 231Pa distribution off Southwest Africa . Earth and Planetary Science Letters, 271 (1-4). pp. 159-169. DOI 10.1016/j.epsl.2008.03.060 <https://doi.org/10.1016/j.epsl.2008.03.060>. doi:10.1016/j.epsl.2008.03.060 |
op_rights |
info:eu-repo/semantics/restrictedAccess |
op_doi |
https://doi.org/10.1016/j.epsl.2008.03.060 |
container_title |
Earth and Planetary Science Letters |
container_volume |
271 |
container_issue |
1-4 |
container_start_page |
159 |
op_container_end_page |
169 |
_version_ |
1766071006354472960 |