Changes in the Ventilation of the Oxygen Minimum Zone of the Tropical North Atlantic.

Brandt, Peter , Hormann, Verena, Körtzinger, Arne , Visbeck, Martin , Krahmann, Gerd , Stramma, Lothar , Lumpkin, Rick and Schmid, Claudia (2010) Changes in the Ventilation of the Oxygen Minimum Zone of the Tropical North Atlantic. Open Access Journal of Physical Oceanography, 40 (8). pp. 1784-1801. DOI 10.1175/2010JPO4301.1.

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Abstract

Changes in the ventilation of the oxygen minimum zone (OMZ) of the tropical North Atlantic are studied using oceanographic data from 18 research cruises carried out between 28.5° and 23°W during 1999–2008 as well as historical data referring to the period 1972–85. In the core of the OMZ at about 400-m depth, a highly significant oxygen decrease of about 15 μmol kg−1 is found between the two periods. During the same time interval, the salinity at the oxygen minimum increased by about 0.1. Above the core of the OMZ, within the central water layer, oxygen decreased too, but salinity changed only slightly or even decreased. The scatter in the local oxygen–salinity relations decreased from the earlier to the later period suggesting a reduced filamentation due to mesoscale eddies and/or zonal jets acting on the background gradients. Here it is suggested that latitudinally alternating zonal jets with observed amplitudes of a few centimeters per second in the depth range of the OMZ contribute to the ventilation of the OMZ. A conceptual model of the ventilation of the OMZ is used to corroborate the hypothesis that changes in the strength of zonal jets affect mean oxygen levels in the OMZ. According to the model, a weakening of zonal jets, which is in general agreement with observed hydrographic evidences, is associated with a reduction of the mean oxygen levels that could significantly contribute to the observed deoxygenation of the North Atlantic OMZ.

Document Type: Article
Keywords: Oceanography; Climatology; Climate change, Jets, North Atlantic Ocean, Ocean models, Ship observations
Research affiliation: OceanRep > SFB 754 > A5
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
OceanRep > SFB 754 > A4
OceanRep > SFB 754 > A3
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
OceanRep > SFB 754
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1175/2010JPO4301.1
ISSN: 0022-3670
Projects: SFB754, Future Ocean, BMBF Nordatlantik
Expeditions/Models/Experiments:
Date Deposited: 01 Oct 2010 09:48
Last Modified: 12 Apr 2018 12:26
URI: http://oceanrep.geomar.de/id/eprint/9201

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