O2 variance and meridional O2 supply in the Tropical North East Atlantic

Hahn, Johannes, Brandt, Peter, Greatbatch, R. J., Krahmann, Gerd and Körtzinger, Arne (2012) O2 variance and meridional O2 supply in the Tropical North East Atlantic [Talk] In: Tropical Atlantic Variability Meeting, PIRATA-17 Meeting , 10.09.-15.09.2012, Kiel.

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Abstract

The oxygen minimum zone (OMZ) of the tropical North East Atlantic (TNEA) is located in the region between the oxygen-rich equatorial band and the Cape Verde Frontal Zone at about 20°N at a depth of 300 – 600 m. The focus of our study is on the lateral ventilation of the OMZ across its southern boundary. This boundary is characterized by a maximum of the mean meridional oxygen gradient at about 5°N. In this region energetic mesoscale activity with periods from one to two months is present. The interaction of the mesoscale activity with the mean meridional oxygen gradient gives rise to a rich oxygen variance from finescale to mesoscale (O(1km) – O(100km)).
An intense measurement program along 23°W cutting through the TNEA OMZ has been executed during recent years. Oxygen variability on time scales of O(1h) to O(1month) was observed with moored optode sensors from PIRATA moorings at 4°N and 11.5°N as well as from moorings located at the equator, 2°N, 5°N and 8°N. High variability of the current field was measured via moored acoustic Doppler current profilers. Additionally, repeat ship sections along the 23°W meridian were performed with standard CTD, oxygen and shipboard current measurements.
The observed oxygen variability as a function of depth and latitude shows characteristic patterns consisting of an intermediate maximum at the upper boundary of the OMZ, a decay of oxygen variability with depth in the upper OMZ and a second weaker maximum in the lower OMZ. Comparing latitudes shows, that the oxygen variability at the OMZ core depth is strongest at about 4°N to 5°N and weaker towards the interior OMZ at 8°N and 11.5°N as well as towards the equator.
A high-resolution advection-diffusion model was developed to simulate oxygen fluxes as a result of the mesoscale eddy field acting on the mean meridional oxygen gradient. While this model is able to describe the production of oxygen variability on length and time scales as small as O(1km) and O(1h), respectively, it reproduces several characteristics of the observed oxygen variability pattern.

Document Type: Conference or Workshop Item (Talk)
Keywords: Oxygen Minimum Zone, OMZ, Oxygen Variance, Oxygen Variability, Oxygen Flux, Oxygen Supply, Tropical Atlantic
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
OceanRep > SFB 754
Related URLs:
Projects: CLIVAR, SFB754
Date Deposited: 04 Jan 2013 09:25
Last Modified: 10 Feb 2015 09:17
URI: http://eprints.uni-kiel.de/id/eprint/19892

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