Objective estimates of mantle 3 He in the ocean and implications for constraining the deep ocean circulation
Hydrothermal vents along the ocean's tectonic ridge systems inject superheated water and large amounts of dissolved metals that impact the deep ocean circulation and the oceanic cycling of trace metals. The hydrothermal fluid contains dissolved mantle helium that is enriched in 3He relative to...
Published in: | Earth and Planetary Science Letters |
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Online Access: | http://hdl.handle.net/1959.4/unsworks_42367 https://doi.org/10.1016/j.epsl.2016.10.054 |
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ftunswworks:oai:unsworks.library.unsw.edu.au:1959.4/unsworks_42367 2024-04-28T08:39:44+00:00 Objective estimates of mantle 3 He in the ocean and implications for constraining the deep ocean circulation Holzer, M DeVries, T Bianchi, D Newton, R Schlosser, P Winckler, G 2017-01-15 http://hdl.handle.net/1959.4/unsworks_42367 https://doi.org/10.1016/j.epsl.2016.10.054 unknown Elsevier http://purl.org/au-research/grants/arc/DP120100674 http://hdl.handle.net/1959.4/unsworks_42367 https://doi.org/10.1016/j.epsl.2016.10.054 metadata only access http://purl.org/coar/access_right/c_14cb CC-BY-NC-ND https://creativecommons.org/licenses/by-nc-nd/4.0/ urn:ISSN:0012-821X urn:ISSN:1385-013X Earth and Planetary Science Letters, 458, 305-314 14 Life Below Water anzsrc-for: 02 Physical Sciences anzsrc-for: 04 Earth Sciences journal article http://purl.org/coar/resource_type/c_6501 2017 ftunswworks https://doi.org/10.1016/j.epsl.2016.10.054 2024-04-09T23:59:07Z Hydrothermal vents along the ocean's tectonic ridge systems inject superheated water and large amounts of dissolved metals that impact the deep ocean circulation and the oceanic cycling of trace metals. The hydrothermal fluid contains dissolved mantle helium that is enriched in 3He relative to the atmosphere, providing an isotopic tracer of the ocean's deep circulation and a marker of hydrothermal sources. This work investigates the potential for the 3He/4He isotope ratio to constrain the ocean's mantle 3He source and to provide constraints on the ocean's deep circulation. We use an ensemble of 11 data-assimilated steady-state ocean circulation models and a mantle helium source based on geographically varying sea-floor spreading rates. The global source distribution is partitioned into 6 regions, and the vertical profile and source amplitude of each region are varied independently to determine the optimal 3He source distribution that minimizes the mismatch between modeled and observed δ3He. In this way, we are able to fit the observed δ3He distribution to within a relative error of ∼15%, with a global 3He source that ranges from 640 to 850 mol yr−1, depending on circulation. The fit captures the vertical and interbasin gradients of the δ3He distribution very well and reproduces its jet-sheared saddle point in the deep equatorial Pacific. This demonstrates that the data-assimilated models have much greater fidelity to the deep ocean circulation than other coarse-resolution ocean models. Nonetheless, the modelled δ3He distributions still display some systematic biases, especially in the deep North Pacific where δ3He is overpredicted by our models, and in the southeastern tropical Pacific, where observed westward-spreading δ3He plumes are not well captured. Sources inferred by the data-assimilated transport with and without isopycnally aligned eddy diffusivity differ widely in the Southern Ocean, in spite of the ability to match the observed distributions of CFCs and radiocarbon for either eddy parameterization. Article in Journal/Newspaper Southern Ocean UNSW Sydney (The University of New South Wales): UNSWorks Earth and Planetary Science Letters 458 305 314 |
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Open Polar |
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UNSW Sydney (The University of New South Wales): UNSWorks |
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ftunswworks |
language |
unknown |
topic |
14 Life Below Water anzsrc-for: 02 Physical Sciences anzsrc-for: 04 Earth Sciences |
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14 Life Below Water anzsrc-for: 02 Physical Sciences anzsrc-for: 04 Earth Sciences Holzer, M DeVries, T Bianchi, D Newton, R Schlosser, P Winckler, G Objective estimates of mantle 3 He in the ocean and implications for constraining the deep ocean circulation |
topic_facet |
14 Life Below Water anzsrc-for: 02 Physical Sciences anzsrc-for: 04 Earth Sciences |
description |
Hydrothermal vents along the ocean's tectonic ridge systems inject superheated water and large amounts of dissolved metals that impact the deep ocean circulation and the oceanic cycling of trace metals. The hydrothermal fluid contains dissolved mantle helium that is enriched in 3He relative to the atmosphere, providing an isotopic tracer of the ocean's deep circulation and a marker of hydrothermal sources. This work investigates the potential for the 3He/4He isotope ratio to constrain the ocean's mantle 3He source and to provide constraints on the ocean's deep circulation. We use an ensemble of 11 data-assimilated steady-state ocean circulation models and a mantle helium source based on geographically varying sea-floor spreading rates. The global source distribution is partitioned into 6 regions, and the vertical profile and source amplitude of each region are varied independently to determine the optimal 3He source distribution that minimizes the mismatch between modeled and observed δ3He. In this way, we are able to fit the observed δ3He distribution to within a relative error of ∼15%, with a global 3He source that ranges from 640 to 850 mol yr−1, depending on circulation. The fit captures the vertical and interbasin gradients of the δ3He distribution very well and reproduces its jet-sheared saddle point in the deep equatorial Pacific. This demonstrates that the data-assimilated models have much greater fidelity to the deep ocean circulation than other coarse-resolution ocean models. Nonetheless, the modelled δ3He distributions still display some systematic biases, especially in the deep North Pacific where δ3He is overpredicted by our models, and in the southeastern tropical Pacific, where observed westward-spreading δ3He plumes are not well captured. Sources inferred by the data-assimilated transport with and without isopycnally aligned eddy diffusivity differ widely in the Southern Ocean, in spite of the ability to match the observed distributions of CFCs and radiocarbon for either eddy parameterization. |
format |
Article in Journal/Newspaper |
author |
Holzer, M DeVries, T Bianchi, D Newton, R Schlosser, P Winckler, G |
author_facet |
Holzer, M DeVries, T Bianchi, D Newton, R Schlosser, P Winckler, G |
author_sort |
Holzer, M |
title |
Objective estimates of mantle 3 He in the ocean and implications for constraining the deep ocean circulation |
title_short |
Objective estimates of mantle 3 He in the ocean and implications for constraining the deep ocean circulation |
title_full |
Objective estimates of mantle 3 He in the ocean and implications for constraining the deep ocean circulation |
title_fullStr |
Objective estimates of mantle 3 He in the ocean and implications for constraining the deep ocean circulation |
title_full_unstemmed |
Objective estimates of mantle 3 He in the ocean and implications for constraining the deep ocean circulation |
title_sort |
objective estimates of mantle 3 he in the ocean and implications for constraining the deep ocean circulation |
publisher |
Elsevier |
publishDate |
2017 |
url |
http://hdl.handle.net/1959.4/unsworks_42367 https://doi.org/10.1016/j.epsl.2016.10.054 |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_source |
urn:ISSN:0012-821X urn:ISSN:1385-013X Earth and Planetary Science Letters, 458, 305-314 |
op_relation |
http://purl.org/au-research/grants/arc/DP120100674 http://hdl.handle.net/1959.4/unsworks_42367 https://doi.org/10.1016/j.epsl.2016.10.054 |
op_rights |
metadata only access http://purl.org/coar/access_right/c_14cb CC-BY-NC-ND https://creativecommons.org/licenses/by-nc-nd/4.0/ |
op_doi |
https://doi.org/10.1016/j.epsl.2016.10.054 |
container_title |
Earth and Planetary Science Letters |
container_volume |
458 |
container_start_page |
305 |
op_container_end_page |
314 |
_version_ |
1797570638023491584 |