# Interannual to decadal oxygen variability in the mid-depth water masses of the eastern North Atlantic

Author(s) Stendardo, Ilaria, Kieke, Dagmar, Rhein, Monika, Gruber, Nicolas, Steinfeldt, Reiner
Publication Type Journal Items, Publication Status: Published
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Title Interannual to decadal oxygen variability in the mid-depth water masses of the eastern North Atlantic
Author(s) Stendardo, Ilaria
Kieke, Dagmar
Rhein, Monika
Gruber, Nicolas
Steinfeldt, Reiner
Journal or Series Title Deep Sea Research Part I: Oceanographic Research Papers
Volume Number 95
Start Page 85
End Page 98
ISSN 0967-0637
0198-0149
Publisher Elsevier
Publication Place Kidlington
Publication Date 2015-01
Keyword(s) Oxygen variability
North Atlantic circulation
Subpolar Mode Water
Mediterranean Outflow Water
Intermediate Water
North Atlantic Oscillation
Mesoscale eddies
Abstract The detection of multi-decadal trends in the oceanic oxygen content and its possible attribution to global warming is protracted by the presence of a substantial amount of interannual to decadal variability, which hitherto is poorly known and characterized. Here we address this gap by studying interannual to decadal changes of the oxygen concentration in the Subpolar Mode Water (SPMW), the Intermediate Water (IW) and the Mediterranean Outflow Water (MOW) in the eastern North Atlantic. We use data from a hydrographic section located in the eastern North Atlantic at about 48°N repeated 12 times over a period of 19 years from 1993 through 2011, with a nearly annual resolution up to 2005. Despite a substantial amount of year-to-year variability, we observe a long-term decrease in the oxygen concentration of all three water masses, with the largest changes occurring from 1993 to 2002. During that time period, the trends were mainly caused by a contraction of the subpolar gyre associated with a northwestward shift of the Subpolar Front (SPF) in the eastern North Atlantic. This caused SPMW to be ventilated at lighter densities and its original density range being invaded by subtropical waters with substantially lower oxygen concentrations. The contraction of the subpolar gyre reduced also the penetration of IW of subpolar origin into the region in favor of an increased northward transport of IW of subtropical origin, which is also lower in oxygen. The long-term oxygen changes in the MOW were mainly affected by the interplay between circulation and solubility changes. Besides the long-term signals, mesoscale variability leaves a substantial imprint as well, affecting the water column over at least the upper 1000 m and laterally by more than 400 km. Mesoscale eddies induced changes in the oxygen concentration of a magnitude that can substantially alias analyses of long-term changes based on repeat hydrographic data that are being collected at intervals of typically 10 years.
DOI 10.1016/j.dsr.2014.10.009
Additional Notes Received 3 July 2014, Received in revised form 10 October 2014, Accepted 29 October 2014, Available online 7 November 2014
Document Type Article
Publication Status Published
Language English
Assigned Organisational Unit(s) 03731
Organisational Unit(s)
NEBIS System Number 000944022
Source Database ID SCOPUS-84911868746
WOS-000348628100008
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@article{Stndrd2015,
author = "Stendardo, Ilaria and Kieke, Dagmar and Rhein, Monika and Gruber, Nicolas and Steinfeldt, Reiner",
title = "{I}nterannual to decadal oxygen variability in the mid-depth water masses of the eastern {N}orth {A}tlantic",
journal = "Deep Sea Research Part I: Oceanographic Research Papers",
year = 2015,
volume = "95",
pages = "85--98",
month = jan,
}


E-Citations record created: Tue, 06 Jan 2015, 10:29:32 CET