Bittig, Henry C., Körtzinger, Arne and Claustre, Herve (2014) Sub-surface production in the Atlantic subtropical gyres - How biogeochemical floats yield estimates of the O2 and NO3 cycle on sub-annual scales. [Talk] In: Ocean Sciences Meeting 2014. , 23.-28.02.2014, Honululu, Hawaii, USA .

Abstract

A number of state-of-the art biogeochemical floats featuring CTD, biooptical, oxygen, and/or nitrate sensors have been recently deployed in various regions of the Atlantic and Indian Ocean during the RemOcean project. In this presentation, we want to focus on the chemical data from five floats located in the North and South Atlantic subtropical gyres, for which a full seasonal cycle is available. Their data, especially O2 and NO3, are presented and analyzed using a 1-D model to estimate primary production as well as elemental budgets and fluxes for the productive layer in-situ and on seasonal scales. The same model is used to shed light on the observed approx. 50 m upward displacement of the sub-surface O2 maximum relative to the deep chlorophyll a maximum by analyzing source/sink terms required within the model to reproduce the observations. Finally, sequences of float profiles acquired within 24 hours at dawn, noon, dusk, and the next dawn were used to investigate diel variations, i.e., photosynthetic production vs. respiration signals over a full 24-hour cycle. To be able to distinguish these processes, thresholds to O2 data accuracy are presented and a recommendation for a extension of the standard Argo sampling scheme to provide such process information is made based on these results.

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