Radionuclides of surface sediments and water samples in the South Atlantic south of the Polar Front
The fractionation of 230Th and 231Pa was investigated throughout the Atlantic sector of the Southern Ocean. Published scavenging models generally assume that the 231Pa/230T ratio of surface sediments is primarily determined by the mass flux of particles. This relationship holds north of the Polar Fr...
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Format: | Other/Unknown Material |
Language: | English |
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PANGAEA
1997
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Online Access: | https://doi.pangaea.de/10.1594/PANGAEA.730455 https://doi.org/10.1594/PANGAEA.730455 |
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ftpangaea:oai:pangaea.de:doi:10.1594/PANGAEA.730455 |
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record_format |
openpolar |
institution |
Open Polar |
collection |
PANGAEA - Data Publisher for Earth & Environmental Science |
op_collection_id |
ftpangaea |
language |
English |
topic |
Agulhas Basin ANT-IX/2 ANT-IX/3 ANT-VIII/3 ANT-X/5 ANT-X/6 ANT-XI/4 Atlantic Ridge AWI_MarGeoChem AWI_Paleo Cosmonauts Sea CTD/Rosette CTD-RO Filchner Trough Giant box corer GKG Halley Bay Indian-Antarctic Ridge In situ pump ISP KL Lazarev Sea Marine Geochemistry @ AWI Maud Rise Meteor Rise MIC MiniCorer MUC MultiCorer Paleoenvironmental Reconstructions from Marine Sediments @ AWI Piston corer (BGR type) Polarstern PS16 PS16/267 PS16/271 PS16/281 PS16/294 PS16/306 PS16/311 PS16/321 PS16/334 PS16/342 PS16/351 PS16/354 PS16/362 PS1751-2 PS1752-5 PS1755-1 PS1759-1 PS1765-1 |
spellingShingle |
Agulhas Basin ANT-IX/2 ANT-IX/3 ANT-VIII/3 ANT-X/5 ANT-X/6 ANT-XI/4 Atlantic Ridge AWI_MarGeoChem AWI_Paleo Cosmonauts Sea CTD/Rosette CTD-RO Filchner Trough Giant box corer GKG Halley Bay Indian-Antarctic Ridge In situ pump ISP KL Lazarev Sea Marine Geochemistry @ AWI Maud Rise Meteor Rise MIC MiniCorer MUC MultiCorer Paleoenvironmental Reconstructions from Marine Sediments @ AWI Piston corer (BGR type) Polarstern PS16 PS16/267 PS16/271 PS16/281 PS16/294 PS16/306 PS16/311 PS16/321 PS16/334 PS16/342 PS16/351 PS16/354 PS16/362 PS1751-2 PS1752-5 PS1755-1 PS1759-1 PS1765-1 Walter, Hans-Jürgen Rutgers van der Loeff, Michiel M Hoeltzen, H Radionuclides of surface sediments and water samples in the South Atlantic south of the Polar Front |
topic_facet |
Agulhas Basin ANT-IX/2 ANT-IX/3 ANT-VIII/3 ANT-X/5 ANT-X/6 ANT-XI/4 Atlantic Ridge AWI_MarGeoChem AWI_Paleo Cosmonauts Sea CTD/Rosette CTD-RO Filchner Trough Giant box corer GKG Halley Bay Indian-Antarctic Ridge In situ pump ISP KL Lazarev Sea Marine Geochemistry @ AWI Maud Rise Meteor Rise MIC MiniCorer MUC MultiCorer Paleoenvironmental Reconstructions from Marine Sediments @ AWI Piston corer (BGR type) Polarstern PS16 PS16/267 PS16/271 PS16/281 PS16/294 PS16/306 PS16/311 PS16/321 PS16/334 PS16/342 PS16/351 PS16/354 PS16/362 PS1751-2 PS1752-5 PS1755-1 PS1759-1 PS1765-1 |
description |
The fractionation of 230Th and 231Pa was investigated throughout the Atlantic sector of the Southern Ocean. Published scavenging models generally assume that the 231Pa/230T ratio of surface sediments is primarily determined by the mass flux of particles. This relationship holds north of the Polar Front, where low primary productivity coincides with ratios of unsupported 231Pa/230Th-xs(231Pa/230Th) - in surface sediments below the production ratio of both radionuclides in the water column. However, we observed high xs231Pa/230Th ratios, conventionally interpreted as a high-productivity signal, in surface sediments south of the Polar Front, especially throughout the Weddell Sea, in contradiction with the low particle flux of this region. Measurements of both dissolved and particulate fractions of 231Pa and 230Th in the water column revealed a strong N-S decrease in the Th/Pa fractionation factor, from typical open ocean values around 10 north of the Polar Front to values between 1 and 2 south of 60°S. This observation clearly indicates that the high xs231Pa/230Th ratios in surface sediments south of the Antarctic Circumpolar Current are produced by a N-S increase in the relative scavenging efficiency of 231Pa relative to 230Th, most probably due to a change in the chemical composition of particulate matter, and not by a high mass flux. It is speculated that biogenic opal, suggested not to significantly fractionate231Pa and 230Th, may explain the enhanced scavenging of 231Pa to the south. This assumption is further supported by extremely high 231Pa/230Th ratios up to 0.34 in material collected with sediment traps south of the Polar Front, where fluxes are primarily determined by biogenic opal. Based on these results we conclude that, in regions where the sedimenting flux is dominated by biogenic opal, the 231Pa/230Th ratio is not a reliable indicator for the mass flux of particles, thus limiting its use as a paleoproductivity proxy in the Southern Ocean. |
format |
Other/Unknown Material |
author |
Walter, Hans-Jürgen Rutgers van der Loeff, Michiel M Hoeltzen, H |
author_facet |
Walter, Hans-Jürgen Rutgers van der Loeff, Michiel M Hoeltzen, H |
author_sort |
Walter, Hans-Jürgen |
title |
Radionuclides of surface sediments and water samples in the South Atlantic south of the Polar Front |
title_short |
Radionuclides of surface sediments and water samples in the South Atlantic south of the Polar Front |
title_full |
Radionuclides of surface sediments and water samples in the South Atlantic south of the Polar Front |
title_fullStr |
Radionuclides of surface sediments and water samples in the South Atlantic south of the Polar Front |
title_full_unstemmed |
Radionuclides of surface sediments and water samples in the South Atlantic south of the Polar Front |
title_sort |
radionuclides of surface sediments and water samples in the south atlantic south of the polar front |
publisher |
PANGAEA |
publishDate |
1997 |
url |
https://doi.pangaea.de/10.1594/PANGAEA.730455 https://doi.org/10.1594/PANGAEA.730455 |
op_coverage |
MEDIAN LATITUDE: -56.099414 * MEDIAN LONGITUDE: -5.024938 * SOUTH-BOUND LATITUDE: -76.415000 * WEST-BOUND LONGITUDE: -58.976667 * NORTH-BOUND LATITUDE: -43.171667 * EAST-BOUND LONGITUDE: 38.826667 * DATE/TIME START: 1989-11-04T21:28:00 * DATE/TIME END: 1994-05-14T00:00:00 |
long_lat |
ENVELOPE(-58.976667,38.826667,-43.171667,-76.415000) |
genre |
Antarc* Antarctic Cosmonauts sea Lazarev Sea Southern Ocean Weddell Sea |
genre_facet |
Antarc* Antarctic Cosmonauts sea Lazarev Sea Southern Ocean Weddell Sea |
op_source |
Supplement to: Walter, Hans-Jürgen; Rutgers van der Loeff, Michiel M; Hoeltzen, H (1997): Enhanced scavenging of 231Pa relative to 230 Th in the South Atlantic south of the Polar Front: implications for the use of the 231Pa/230Th ratio as a paleoproductivity proxy. Earth and Planetary Science Letters, 149(1-4), 85-100, https://doi.org/10.1016/S0012-821X(97)00068-X |
op_relation |
https://doi.pangaea.de/10.1594/PANGAEA.730455 https://doi.org/10.1594/PANGAEA.730455 |
op_rights |
CC-BY-3.0: Creative Commons Attribution 3.0 Unported Access constraints: unrestricted info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1594/PANGAEA.73045510.1016/S0012-821X(97)00068-X |
_version_ |
1810289143030218752 |
spelling |
ftpangaea:oai:pangaea.de:doi:10.1594/PANGAEA.730455 2024-09-15T17:48:06+00:00 Radionuclides of surface sediments and water samples in the South Atlantic south of the Polar Front Walter, Hans-Jürgen Rutgers van der Loeff, Michiel M Hoeltzen, H MEDIAN LATITUDE: -56.099414 * MEDIAN LONGITUDE: -5.024938 * SOUTH-BOUND LATITUDE: -76.415000 * WEST-BOUND LONGITUDE: -58.976667 * NORTH-BOUND LATITUDE: -43.171667 * EAST-BOUND LONGITUDE: 38.826667 * DATE/TIME START: 1989-11-04T21:28:00 * DATE/TIME END: 1994-05-14T00:00:00 1997 application/zip, 2 datasets https://doi.pangaea.de/10.1594/PANGAEA.730455 https://doi.org/10.1594/PANGAEA.730455 en eng PANGAEA https://doi.pangaea.de/10.1594/PANGAEA.730455 https://doi.org/10.1594/PANGAEA.730455 CC-BY-3.0: Creative Commons Attribution 3.0 Unported Access constraints: unrestricted info:eu-repo/semantics/openAccess Supplement to: Walter, Hans-Jürgen; Rutgers van der Loeff, Michiel M; Hoeltzen, H (1997): Enhanced scavenging of 231Pa relative to 230 Th in the South Atlantic south of the Polar Front: implications for the use of the 231Pa/230Th ratio as a paleoproductivity proxy. Earth and Planetary Science Letters, 149(1-4), 85-100, https://doi.org/10.1016/S0012-821X(97)00068-X Agulhas Basin ANT-IX/2 ANT-IX/3 ANT-VIII/3 ANT-X/5 ANT-X/6 ANT-XI/4 Atlantic Ridge AWI_MarGeoChem AWI_Paleo Cosmonauts Sea CTD/Rosette CTD-RO Filchner Trough Giant box corer GKG Halley Bay Indian-Antarctic Ridge In situ pump ISP KL Lazarev Sea Marine Geochemistry @ AWI Maud Rise Meteor Rise MIC MiniCorer MUC MultiCorer Paleoenvironmental Reconstructions from Marine Sediments @ AWI Piston corer (BGR type) Polarstern PS16 PS16/267 PS16/271 PS16/281 PS16/294 PS16/306 PS16/311 PS16/321 PS16/334 PS16/342 PS16/351 PS16/354 PS16/362 PS1751-2 PS1752-5 PS1755-1 PS1759-1 PS1765-1 dataset publication series 1997 ftpangaea https://doi.org/10.1594/PANGAEA.73045510.1016/S0012-821X(97)00068-X 2024-08-21T00:02:25Z The fractionation of 230Th and 231Pa was investigated throughout the Atlantic sector of the Southern Ocean. Published scavenging models generally assume that the 231Pa/230T ratio of surface sediments is primarily determined by the mass flux of particles. This relationship holds north of the Polar Front, where low primary productivity coincides with ratios of unsupported 231Pa/230Th-xs(231Pa/230Th) - in surface sediments below the production ratio of both radionuclides in the water column. However, we observed high xs231Pa/230Th ratios, conventionally interpreted as a high-productivity signal, in surface sediments south of the Polar Front, especially throughout the Weddell Sea, in contradiction with the low particle flux of this region. Measurements of both dissolved and particulate fractions of 231Pa and 230Th in the water column revealed a strong N-S decrease in the Th/Pa fractionation factor, from typical open ocean values around 10 north of the Polar Front to values between 1 and 2 south of 60°S. This observation clearly indicates that the high xs231Pa/230Th ratios in surface sediments south of the Antarctic Circumpolar Current are produced by a N-S increase in the relative scavenging efficiency of 231Pa relative to 230Th, most probably due to a change in the chemical composition of particulate matter, and not by a high mass flux. It is speculated that biogenic opal, suggested not to significantly fractionate231Pa and 230Th, may explain the enhanced scavenging of 231Pa to the south. This assumption is further supported by extremely high 231Pa/230Th ratios up to 0.34 in material collected with sediment traps south of the Polar Front, where fluxes are primarily determined by biogenic opal. Based on these results we conclude that, in regions where the sedimenting flux is dominated by biogenic opal, the 231Pa/230Th ratio is not a reliable indicator for the mass flux of particles, thus limiting its use as a paleoproductivity proxy in the Southern Ocean. Other/Unknown Material Antarc* Antarctic Cosmonauts sea Lazarev Sea Southern Ocean Weddell Sea PANGAEA - Data Publisher for Earth & Environmental Science ENVELOPE(-58.976667,38.826667,-43.171667,-76.415000) |