Observations of oxygen variability in the eastern tropical North Atlantic.

Hahn, Johannes , Brandt, Peter , Karstensen, Johannes and Körtzinger, Arne (2017) Observations of oxygen variability in the eastern tropical North Atlantic. [Poster] In: PIRATA 22 - PREFACE - TAV Meeting. , 05.-10.11.2017, Fortaleza, Brasil .

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A vast data set of long-term oxygen records from moored and shipboard observations in the eastern tropical North Atlantic (ETNA) is presented. The data set also includes oxygen observations from the current PIRATA mooring period, which were successfully implemented for the first time in the online data stream of the PIRATA T-Flex buoys.
Time series of moored instruments reveal characteristic regimes of dominant oxygen variability on different time scales. Above about 200m, anomalous low oxygen events on intraseasonal time scales frequently occur, which are associated with mesoscale eddies and baroclinic Rossby waves. Below about 500m at the horizontal core position of the oxygen minimum zone, the intraseasonal variability is relatively weaker and a well-defined seasonal cycle in oxygen is observed. The seasonal cycle calculated at the fixed depths of the moored instruments was found to be mainly driven by horizontal transport variability along isopycnal surfaces, with vertical excursions of isopycnals representing only a minor contribution. Using repeat shipboard hydrography, a decadal oxygen change was observed below 200m with a well-defined oxygen decrease/increase above/below 400m, which could be mainly associated with weakened/intensified circulation at the different depth levels. Such gradual long-term changes in oxygen are best captured by repeat hydrography, while moored observations are ideal means to study short-term processes and associated oxygen variability.

Document Type: Conference or Workshop Item (Poster)
Keywords: oxygen, oxygen variability, oxygen time series, oxygen minimum zone, eastern tropical North Atlantic
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Projects: SFB754, AtlantOS, PIRATA
Date Deposited: 04 Jan 2018 11:48
Last Modified: 04 Jan 2018 11:48
URI: http://oceanrep.geomar.de/id/eprint/41121

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