Quantification of dissolved oxygen dynamics in a semi-enclosed sea - A comparison of observational platforms

It was found that in comparison to a classical standard CTD system, a towed undulating CTD system (ScanFish) is better suited to resolve the meso- and submeso-scale distribution patterns of DO concentrations. In particular, in the sub-halocline layers where the variability of DO concentrations was consistently high (1-70 µM). The highly dynamic post-inflow situation was also observed by the glider and the profiling mooring. For comparison purposes four different sub-halocline layers in a depth range from 80 m to 180 m depth were defined and the mean oxygen content of these layers was calculated for both platforms. It turned out, that the mean DO concentrations for the different layers, which were determined from glider and mooring measurements, differ only slightly from each other. Differences were greatest (up to 7 µM) below the halocline (80-120m) and could be explained by the spatial and temporal variability of DO concentrations in this area and by the large response time of the gliders oxygen optode. However, the temporal development of inflow events could be determined and investigated in more detail by using autonomous platforms. The frequency and size of smaller inflows, for instance, that move along the halocline or in deeper layers thus could be evaluated.