Oxygen Minimum Zone of the tropical North Atlantic - Cruise MSM22 - October 24, 2012 - November 23, 2012 - Mindelo (Cape Verde Islands) - Mindelo (Cape Verde Islands) (English)

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Cruise MSM22 is a joint effort of the Kiel Collaborative Research Centre SFB 754 ("Climate - Biogeochemistry Interactions in the Tropical Ocean") involving the BMBF joint projects NORDATLANTIK/RACE and SOPRAN as well as of the German-French-African Cooperative Project AWA. The main goal within the framework of the SFB 754 was the quantification of oxygen supply to the oxygen minimum zone (OMZ) of the Eastern Tropical North Atlantic (ETNA). Ventilation processes to be investigated include lateral and vertical mixing and oxygen advection (SP A3 and A4). The role of zooplankton for oxygen consumption and biogeochemical cycles (SP B8) was another focus of this cruise. All planned hydrographic and current data could be acquired as planned, including the successful recovery of all moorings with an overall very large data gain. The glider swarm experiment at the southern rim was performed as planned after deploying the mooring array. By the combined analysis of glider and mooring data (after mooring recovery in 2014) regarding spatial and temporal variability of water properties and currents we expect new inside into the lateral ventilation by mesoscale and submescale processes. An additional objective was the identification and investigation of mesoscale eddies which are generated in the coastal upwelling region off West Africa and then migrate westward. Unfortunately, although several eddies were investigated during the cruise, they did not show similar extreme biogeochemical properties as those found occasionally at the CVOO mooring site. At the equator, the cruise focussed on the equatorial current system, its interannual to decadal variability and its role in the zonal transport of heat, freshwater, and oxygen (BMBF NORDATLANTIK/RACE, SFB 754). Important long-term moored time series at the equator, 23°W could be successfully extended and provide the basis together with top-to-bottom hydrographic station and current data for the study of the role of multi-year ocean variability in the tropical Atlantic climate.