Ventilation of the Subtropical North Atlantic: Locations and Times of Last Ventilation Estimated Using Tracer Constraints From GEOTRACES Section GA03
The ventilation of the subtropical North Atlantic along GEOTRACES section GA03 is quantified in terms of where and how long ago water was last in the mixed layer. Measurements of T, S, PO*4, CFC-11, CFC-12, SF6, and estimates of prebomb 14C are deconvolved for the boundary propagator G using a maxim...
Published in: | Journal of Geophysical Research: Oceans |
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American Geophysical Union (AGU)
2018
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Online Access: | http://hdl.handle.net/1959.4/unsworks_54847 https://unsworks.unsw.edu.au/bitstreams/3b3c1aa8-0591-4747-95e1-8ec4df193ecc/download https://doi.org/10.1002/2017JC013698 |
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ftunswworks:oai:unsworks.library.unsw.edu.au:1959.4/unsworks_54847 2024-05-19T07:30:21+00:00 Ventilation of the Subtropical North Atlantic: Locations and Times of Last Ventilation Estimated Using Tracer Constraints From GEOTRACES Section GA03 Holzer, M Smethie, WM Ting, YH 2018-04-01 application/pdf http://hdl.handle.net/1959.4/unsworks_54847 https://unsworks.unsw.edu.au/bitstreams/3b3c1aa8-0591-4747-95e1-8ec4df193ecc/download https://doi.org/10.1002/2017JC013698 unknown American Geophysical Union (AGU) http://hdl.handle.net/1959.4/unsworks_54847 https://unsworks.unsw.edu.au/bitstreams/3b3c1aa8-0591-4747-95e1-8ec4df193ecc/download https://doi.org/10.1002/2017JC013698 open access https://purl.org/coar/access_right/c_abf2 CC-BY-NC-ND https://creativecommons.org/licenses/by-nc-nd/4.0/ free_to_read urn:ISSN:2169-9275 urn:ISSN:2169-9291 Journal of Geophysical Research: Oceans, 123, 4, 2332-2352 anzsrc-for: 0404 Geophysics anzsrc-for: 0405 Oceanography anzsrc-for: 0406 Physical Geography and Environmental Geoscience journal article http://purl.org/coar/resource_type/c_6501 2018 ftunswworks https://doi.org/10.1002/2017JC013698 2024-04-24T00:37:12Z The ventilation of the subtropical North Atlantic along GEOTRACES section GA03 is quantified in terms of where and how long ago water was last in the mixed layer. Measurements of T, S, PO*4, CFC-11, CFC-12, SF6, and estimates of prebomb 14C are deconvolved for the boundary propagator G using a maximum-entropy approach. From G, we calculate the fractions of water last ventilated in specified surface regions Ωw. We estimate that (56 ± 13)% of the water deeper than 1,000 m was ventilated in northern high latitudes, (15 ± 5)% in the Mediterranean, and (27 ± 12)% in the Southern Ocean. Below the thermocline and outside the deep western boundary current, mean ages of Ωw-ventilated water exceed a century. Consequently, memory of where last ventilation occurred tends to get lost and the deep mean-age patterns of Ωw-ventilated water are broadly similar for all Ωw. The mean ventilation ages, averaged over the section with Ωw-fraction weights, are roughly 200 years for all deep water masses except for water last ventilated south of the Antarctic divergence, which is about twice as old. The uncertainties in the section-mean profiles of the Ωw fractions and their mean ages are ∼50% and ∼20%, respectively. The Ωw fractions have vertically diffuse overlapping patterns suggesting significant diapycnal mixing, consistent with century-scale mean ages. We quantify the seasonal cycle of ventilation and find that in both hemispheres peak ventilation occurs during late winter and early spring, but Northern Hemisphere ventilated deep waters have a more pronounced seasonal cycle with nearly zero summertime ventilation. Article in Journal/Newspaper Antarc* Antarctic North Atlantic Southern Ocean UNSW Sydney (The University of New South Wales): UNSWorks Journal of Geophysical Research: Oceans 123 4 2332 2352 |
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Open Polar |
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UNSW Sydney (The University of New South Wales): UNSWorks |
op_collection_id |
ftunswworks |
language |
unknown |
topic |
anzsrc-for: 0404 Geophysics anzsrc-for: 0405 Oceanography anzsrc-for: 0406 Physical Geography and Environmental Geoscience |
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anzsrc-for: 0404 Geophysics anzsrc-for: 0405 Oceanography anzsrc-for: 0406 Physical Geography and Environmental Geoscience Holzer, M Smethie, WM Ting, YH Ventilation of the Subtropical North Atlantic: Locations and Times of Last Ventilation Estimated Using Tracer Constraints From GEOTRACES Section GA03 |
topic_facet |
anzsrc-for: 0404 Geophysics anzsrc-for: 0405 Oceanography anzsrc-for: 0406 Physical Geography and Environmental Geoscience |
description |
The ventilation of the subtropical North Atlantic along GEOTRACES section GA03 is quantified in terms of where and how long ago water was last in the mixed layer. Measurements of T, S, PO*4, CFC-11, CFC-12, SF6, and estimates of prebomb 14C are deconvolved for the boundary propagator G using a maximum-entropy approach. From G, we calculate the fractions of water last ventilated in specified surface regions Ωw. We estimate that (56 ± 13)% of the water deeper than 1,000 m was ventilated in northern high latitudes, (15 ± 5)% in the Mediterranean, and (27 ± 12)% in the Southern Ocean. Below the thermocline and outside the deep western boundary current, mean ages of Ωw-ventilated water exceed a century. Consequently, memory of where last ventilation occurred tends to get lost and the deep mean-age patterns of Ωw-ventilated water are broadly similar for all Ωw. The mean ventilation ages, averaged over the section with Ωw-fraction weights, are roughly 200 years for all deep water masses except for water last ventilated south of the Antarctic divergence, which is about twice as old. The uncertainties in the section-mean profiles of the Ωw fractions and their mean ages are ∼50% and ∼20%, respectively. The Ωw fractions have vertically diffuse overlapping patterns suggesting significant diapycnal mixing, consistent with century-scale mean ages. We quantify the seasonal cycle of ventilation and find that in both hemispheres peak ventilation occurs during late winter and early spring, but Northern Hemisphere ventilated deep waters have a more pronounced seasonal cycle with nearly zero summertime ventilation. |
format |
Article in Journal/Newspaper |
author |
Holzer, M Smethie, WM Ting, YH |
author_facet |
Holzer, M Smethie, WM Ting, YH |
author_sort |
Holzer, M |
title |
Ventilation of the Subtropical North Atlantic: Locations and Times of Last Ventilation Estimated Using Tracer Constraints From GEOTRACES Section GA03 |
title_short |
Ventilation of the Subtropical North Atlantic: Locations and Times of Last Ventilation Estimated Using Tracer Constraints From GEOTRACES Section GA03 |
title_full |
Ventilation of the Subtropical North Atlantic: Locations and Times of Last Ventilation Estimated Using Tracer Constraints From GEOTRACES Section GA03 |
title_fullStr |
Ventilation of the Subtropical North Atlantic: Locations and Times of Last Ventilation Estimated Using Tracer Constraints From GEOTRACES Section GA03 |
title_full_unstemmed |
Ventilation of the Subtropical North Atlantic: Locations and Times of Last Ventilation Estimated Using Tracer Constraints From GEOTRACES Section GA03 |
title_sort |
ventilation of the subtropical north atlantic: locations and times of last ventilation estimated using tracer constraints from geotraces section ga03 |
publisher |
American Geophysical Union (AGU) |
publishDate |
2018 |
url |
http://hdl.handle.net/1959.4/unsworks_54847 https://unsworks.unsw.edu.au/bitstreams/3b3c1aa8-0591-4747-95e1-8ec4df193ecc/download https://doi.org/10.1002/2017JC013698 |
genre |
Antarc* Antarctic North Atlantic Southern Ocean |
genre_facet |
Antarc* Antarctic North Atlantic Southern Ocean |
op_source |
urn:ISSN:2169-9275 urn:ISSN:2169-9291 Journal of Geophysical Research: Oceans, 123, 4, 2332-2352 |
op_relation |
http://hdl.handle.net/1959.4/unsworks_54847 https://unsworks.unsw.edu.au/bitstreams/3b3c1aa8-0591-4747-95e1-8ec4df193ecc/download https://doi.org/10.1002/2017JC013698 |
op_rights |
open access https://purl.org/coar/access_right/c_abf2 CC-BY-NC-ND https://creativecommons.org/licenses/by-nc-nd/4.0/ free_to_read |
op_doi |
https://doi.org/10.1002/2017JC013698 |
container_title |
Journal of Geophysical Research: Oceans |
container_volume |
123 |
container_issue |
4 |
container_start_page |
2332 |
op_container_end_page |
2352 |
_version_ |
1799485642273456128 |