Open ocean dead zones in the tropical North Atlantic Ocean
Here we present first observations, from instrumentation installed on moorings and a float, of unexpectedly low (<2 μmol kg−1) oxygen environments in the open waters of the tropical North Atlantic, a region where oxygen concentration does normally not fall much below 40 μmol kg−1. The low-oxygen...
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Copernicus Publications (EGU)
2015
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Online Access: | https://oceanrep.geomar.de/id/eprint/26507/ https://oceanrep.geomar.de/id/eprint/26507/1/bg-12-2597-2015.pdf https://doi.org/10.5194/bg-12-2597-2015 |
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ftoceanrep:oai:oceanrep.geomar.de:26507 2023-05-15T17:31:17+02:00 Open ocean dead zones in the tropical North Atlantic Ocean Karstensen, Johannes Fiedler, Björn Schütte, Florian Brandt, Peter Körtzinger, Arne Fischer, G. Zantopp, Rainer J. Hahn, Johannes Visbeck, Martin Wallace, Douglas W.R. 2015-04-30 text https://oceanrep.geomar.de/id/eprint/26507/ https://oceanrep.geomar.de/id/eprint/26507/1/bg-12-2597-2015.pdf https://doi.org/10.5194/bg-12-2597-2015 en eng Copernicus Publications (EGU) https://oceanrep.geomar.de/id/eprint/26507/1/bg-12-2597-2015.pdf Karstensen, J. , Fiedler, B., Schütte, F., Brandt, P. , Körtzinger, A. , Fischer, G., Zantopp, R. J. , Hahn, J. , Visbeck, M. and Wallace, D. W. R. (2015) Open ocean dead zones in the tropical North Atlantic Ocean. Open Access Biogeosciences (BG), 12 . pp. 2597-2605. DOI 10.5194/bg-12-2597-2015 <https://doi.org/10.5194/bg-12-2597-2015>. doi:10.5194/bg-12-2597-2015 cc_by_3.0 info:eu-repo/semantics/openAccess Article PeerReviewed 2015 ftoceanrep https://doi.org/10.5194/bg-12-2597-2015 2023-04-07T15:16:06Z Here we present first observations, from instrumentation installed on moorings and a float, of unexpectedly low (<2 μmol kg−1) oxygen environments in the open waters of the tropical North Atlantic, a region where oxygen concentration does normally not fall much below 40 μmol kg−1. The low-oxygen zones are created at shallow depth, just below the mixed layer, in the euphotic zone of cyclonic eddies and anticyclonic-modewater eddies. Both types of eddies are prone to high surface productivity. Net respiration rates for the eddies are found to be 3 to 5 times higher when compared with surrounding waters. Oxygen is lowest in the centre of the eddies, in a depth range where the swirl velocity, defining the transition between eddy and surroundings, has its maximum. It is assumed that the strong velocity at the outer rim of the eddies hampers the transport of properties across the eddies boundary and as such isolates their cores. This is supported by a remarkably stable hydrographic structure of the eddies core over periods of several months. The eddies propagate westward, at about 4 to 5 km day−1, from their generation region off the West African coast into the open ocean. High productivity and accompanying respiration, paired with sluggish exchange across the eddy boundary, create the "dead zone" inside the eddies, so far only reported for coastal areas or lakes. We observe a direct impact of the open ocean dead zones on the marine ecosystem as such that the diurnal vertical migration of zooplankton is suppressed inside the eddies. Article in Journal/Newspaper North Atlantic OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Biogeosciences 12 8 2597 2605 |
institution |
Open Polar |
collection |
OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
op_collection_id |
ftoceanrep |
language |
English |
description |
Here we present first observations, from instrumentation installed on moorings and a float, of unexpectedly low (<2 μmol kg−1) oxygen environments in the open waters of the tropical North Atlantic, a region where oxygen concentration does normally not fall much below 40 μmol kg−1. The low-oxygen zones are created at shallow depth, just below the mixed layer, in the euphotic zone of cyclonic eddies and anticyclonic-modewater eddies. Both types of eddies are prone to high surface productivity. Net respiration rates for the eddies are found to be 3 to 5 times higher when compared with surrounding waters. Oxygen is lowest in the centre of the eddies, in a depth range where the swirl velocity, defining the transition between eddy and surroundings, has its maximum. It is assumed that the strong velocity at the outer rim of the eddies hampers the transport of properties across the eddies boundary and as such isolates their cores. This is supported by a remarkably stable hydrographic structure of the eddies core over periods of several months. The eddies propagate westward, at about 4 to 5 km day−1, from their generation region off the West African coast into the open ocean. High productivity and accompanying respiration, paired with sluggish exchange across the eddy boundary, create the "dead zone" inside the eddies, so far only reported for coastal areas or lakes. We observe a direct impact of the open ocean dead zones on the marine ecosystem as such that the diurnal vertical migration of zooplankton is suppressed inside the eddies. |
format |
Article in Journal/Newspaper |
author |
Karstensen, Johannes Fiedler, Björn Schütte, Florian Brandt, Peter Körtzinger, Arne Fischer, G. Zantopp, Rainer J. Hahn, Johannes Visbeck, Martin Wallace, Douglas W.R. |
spellingShingle |
Karstensen, Johannes Fiedler, Björn Schütte, Florian Brandt, Peter Körtzinger, Arne Fischer, G. Zantopp, Rainer J. Hahn, Johannes Visbeck, Martin Wallace, Douglas W.R. Open ocean dead zones in the tropical North Atlantic Ocean |
author_facet |
Karstensen, Johannes Fiedler, Björn Schütte, Florian Brandt, Peter Körtzinger, Arne Fischer, G. Zantopp, Rainer J. Hahn, Johannes Visbeck, Martin Wallace, Douglas W.R. |
author_sort |
Karstensen, Johannes |
title |
Open ocean dead zones in the tropical North Atlantic Ocean |
title_short |
Open ocean dead zones in the tropical North Atlantic Ocean |
title_full |
Open ocean dead zones in the tropical North Atlantic Ocean |
title_fullStr |
Open ocean dead zones in the tropical North Atlantic Ocean |
title_full_unstemmed |
Open ocean dead zones in the tropical North Atlantic Ocean |
title_sort |
open ocean dead zones in the tropical north atlantic ocean |
publisher |
Copernicus Publications (EGU) |
publishDate |
2015 |
url |
https://oceanrep.geomar.de/id/eprint/26507/ https://oceanrep.geomar.de/id/eprint/26507/1/bg-12-2597-2015.pdf https://doi.org/10.5194/bg-12-2597-2015 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
https://oceanrep.geomar.de/id/eprint/26507/1/bg-12-2597-2015.pdf Karstensen, J. , Fiedler, B., Schütte, F., Brandt, P. , Körtzinger, A. , Fischer, G., Zantopp, R. J. , Hahn, J. , Visbeck, M. and Wallace, D. W. R. (2015) Open ocean dead zones in the tropical North Atlantic Ocean. Open Access Biogeosciences (BG), 12 . pp. 2597-2605. DOI 10.5194/bg-12-2597-2015 <https://doi.org/10.5194/bg-12-2597-2015>. doi:10.5194/bg-12-2597-2015 |
op_rights |
cc_by_3.0 info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.5194/bg-12-2597-2015 |
container_title |
Biogeosciences |
container_volume |
12 |
container_issue |
8 |
container_start_page |
2597 |
op_container_end_page |
2605 |
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1766128777600958464 |