Oxygen Variance and Meridional Oxygen Supply in the Tropical North East Atlantic Oxygen Minimum Zone

The distribution of the mean oceanic oxygen concentration, which results from a balance between ventilation and consumption, reveals extended oxygen minimum zones (OMZ) in the eastern tropical Pacific and Atlantic at intermediate depth (300m-700m). Here, we analyze hydrographic and velocity data from shipboard and moored observations, which were taken along the 23°W meridian cutting through the Tropical North East Atlantic (TNEA) OMZ, in order to study distribution and generation of oxygen variability as well as the isopycnal oxygen flux. By applying the extended Osborn-Cox model, the respective role of mesoscale stirring and diapycnal mixing in producing enhanced oxygen variability, found at the southern and upper boundary of the OMZ, is quantified. From the well-ventilated equatorial region toward the OMZ core a northward eddy-driven oxygen flux is observed whose divergence corresponds to an oxygen supply of about 2.4 μmolkg-1yr-1 at the OMZ core depth. Combining our results with recent studies, a refined oxygen budget for the TNEA OMZ is derived, in which the eddy-driven oxygen supply contributes more than 50% to the supply required to balance the estimated oxygen consumption