Shelf-basin exchange times of Arctic surface waters estimated from 228Th/228Ra disequilibrium
The Trans Polar Drift is strongly enriched in 228Ra accumulated on the wide Arctic shelves with subsequent rapid off-shore transport. We present new data of Polarstern expeditions to the central Arctic and to the Kara and Laptev Seas. Because 226Ra activities in Pacific waters are 30% higher than in...
Published in: | Journal of Geophysical Research: Oceans |
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2012
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Online Access: | https://epic.awi.de/id/eprint/24715/ https://epic.awi.de/id/eprint/24715/1/RvdLetalThRaArcticJGRPostprint.pdf https://hdl.handle.net/10013/epic.39149 https://hdl.handle.net/10013/epic.39149.d001 |
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ftawi:oai:epic.awi.de:24715 2024-09-15T17:51:29+00:00 Shelf-basin exchange times of Arctic surface waters estimated from 228Th/228Ra disequilibrium Rutgers v. d. Loeff, Michiel Cai, Pinghe Stimac, Ingrid Bauch, D. Hanfland, Claudia Roeske, Tobias Moran, S. B. 2012 application/pdf https://epic.awi.de/id/eprint/24715/ https://epic.awi.de/id/eprint/24715/1/RvdLetalThRaArcticJGRPostprint.pdf https://hdl.handle.net/10013/epic.39149 https://hdl.handle.net/10013/epic.39149.d001 unknown https://epic.awi.de/id/eprint/24715/1/RvdLetalThRaArcticJGRPostprint.pdf https://hdl.handle.net/10013/epic.39149.d001 Rutgers v. d. Loeff, M. orcid:0000-0003-1393-3742 , Cai, P. , Stimac, I. orcid:0000-0001-6053-2330 , Bauch, D. , Hanfland, C. , Roeske, T. and Moran, S. B. (2012) Shelf-basin exchange times of Arctic surface waters estimated from 228Th/228Ra disequilibrium , Journal of Geophysical Research - Oceans., 117 (C03024) . doi:10.1029/2011JC007478 <https://doi.org/10.1029/2011JC007478> , hdl:10013/epic.39149 EPIC3Journal of Geophysical Research - Oceans., 117(C03024) Article isiRev 2012 ftawi https://doi.org/10.1029/2011JC007478 2024-06-24T04:03:41Z The Trans Polar Drift is strongly enriched in 228Ra accumulated on the wide Arctic shelves with subsequent rapid off-shore transport. We present new data of Polarstern expeditions to the central Arctic and to the Kara and Laptev Seas. Because 226Ra activities in Pacific waters are 30% higher than in Atlantic waters, we correct 226Ra for the Pacific admixture when normalizing 228Ra with 226Ra. The use of 228Ra decay as age marker critically depends on the constancy in space and time of the source activity, a condition that has not yet adequately been tested. While 228Ra decays during transit over the central Basin, ingrowth of 228Th could provide an alternative age marker. The high 228Th/228Ra activity ratio (AR=0.8 – 1.0) in the central basins is incompatible with a mixing model based on horizontal eddy diffusion. An advective model predicts that 228Th grows to an equilibrium AR, the value of which depends on the scavenging regime. The low AR over the Lomonosov Ridge (AR=0.5) can be due to either rapid transport (minimum age without scavenging 1.1 year) or enhanced scavenging. Suspended particulate matter (SPM) load (derived from beam transmission and particulate 234Th) and total 234Th depletion data show that scavenging, although extremely low in the central Arctic, is enhanced over the Lomonosov Ridge, making an age of 3 yr more likely. The combined data of 228Ra decay and 228Th ingrowth confirm the existence of a recirculating gyre in the surface water of the eastern Eurasian Basin with a river water residence time of at least 3 years. Article in Journal/Newspaper Arctic laptev Lomonosov Ridge Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) Journal of Geophysical Research: Oceans 117 C3 n/a n/a |
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Open Polar |
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Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) |
op_collection_id |
ftawi |
language |
unknown |
description |
The Trans Polar Drift is strongly enriched in 228Ra accumulated on the wide Arctic shelves with subsequent rapid off-shore transport. We present new data of Polarstern expeditions to the central Arctic and to the Kara and Laptev Seas. Because 226Ra activities in Pacific waters are 30% higher than in Atlantic waters, we correct 226Ra for the Pacific admixture when normalizing 228Ra with 226Ra. The use of 228Ra decay as age marker critically depends on the constancy in space and time of the source activity, a condition that has not yet adequately been tested. While 228Ra decays during transit over the central Basin, ingrowth of 228Th could provide an alternative age marker. The high 228Th/228Ra activity ratio (AR=0.8 – 1.0) in the central basins is incompatible with a mixing model based on horizontal eddy diffusion. An advective model predicts that 228Th grows to an equilibrium AR, the value of which depends on the scavenging regime. The low AR over the Lomonosov Ridge (AR=0.5) can be due to either rapid transport (minimum age without scavenging 1.1 year) or enhanced scavenging. Suspended particulate matter (SPM) load (derived from beam transmission and particulate 234Th) and total 234Th depletion data show that scavenging, although extremely low in the central Arctic, is enhanced over the Lomonosov Ridge, making an age of 3 yr more likely. The combined data of 228Ra decay and 228Th ingrowth confirm the existence of a recirculating gyre in the surface water of the eastern Eurasian Basin with a river water residence time of at least 3 years. |
format |
Article in Journal/Newspaper |
author |
Rutgers v. d. Loeff, Michiel Cai, Pinghe Stimac, Ingrid Bauch, D. Hanfland, Claudia Roeske, Tobias Moran, S. B. |
spellingShingle |
Rutgers v. d. Loeff, Michiel Cai, Pinghe Stimac, Ingrid Bauch, D. Hanfland, Claudia Roeske, Tobias Moran, S. B. Shelf-basin exchange times of Arctic surface waters estimated from 228Th/228Ra disequilibrium |
author_facet |
Rutgers v. d. Loeff, Michiel Cai, Pinghe Stimac, Ingrid Bauch, D. Hanfland, Claudia Roeske, Tobias Moran, S. B. |
author_sort |
Rutgers v. d. Loeff, Michiel |
title |
Shelf-basin exchange times of Arctic surface waters estimated from 228Th/228Ra disequilibrium |
title_short |
Shelf-basin exchange times of Arctic surface waters estimated from 228Th/228Ra disequilibrium |
title_full |
Shelf-basin exchange times of Arctic surface waters estimated from 228Th/228Ra disequilibrium |
title_fullStr |
Shelf-basin exchange times of Arctic surface waters estimated from 228Th/228Ra disequilibrium |
title_full_unstemmed |
Shelf-basin exchange times of Arctic surface waters estimated from 228Th/228Ra disequilibrium |
title_sort |
shelf-basin exchange times of arctic surface waters estimated from 228th/228ra disequilibrium |
publishDate |
2012 |
url |
https://epic.awi.de/id/eprint/24715/ https://epic.awi.de/id/eprint/24715/1/RvdLetalThRaArcticJGRPostprint.pdf https://hdl.handle.net/10013/epic.39149 https://hdl.handle.net/10013/epic.39149.d001 |
genre |
Arctic laptev Lomonosov Ridge |
genre_facet |
Arctic laptev Lomonosov Ridge |
op_source |
EPIC3Journal of Geophysical Research - Oceans., 117(C03024) |
op_relation |
https://epic.awi.de/id/eprint/24715/1/RvdLetalThRaArcticJGRPostprint.pdf https://hdl.handle.net/10013/epic.39149.d001 Rutgers v. d. Loeff, M. orcid:0000-0003-1393-3742 , Cai, P. , Stimac, I. orcid:0000-0001-6053-2330 , Bauch, D. , Hanfland, C. , Roeske, T. and Moran, S. B. (2012) Shelf-basin exchange times of Arctic surface waters estimated from 228Th/228Ra disequilibrium , Journal of Geophysical Research - Oceans., 117 (C03024) . doi:10.1029/2011JC007478 <https://doi.org/10.1029/2011JC007478> , hdl:10013/epic.39149 |
op_doi |
https://doi.org/10.1029/2011JC007478 |
container_title |
Journal of Geophysical Research: Oceans |
container_volume |
117 |
container_issue |
C3 |
container_start_page |
n/a |
op_container_end_page |
n/a |
_version_ |
1810293394160746496 |