Instrument-induced linear flow resistance in ضresund

It is shown that the previously studied linear component of flow resistance in ضresund is an artefact due to underestimates of current velocities obtained from Aanderaa RCM7 and InterOcean S4 in strong current environments. The analysis uses two datasets. The first set contains current observations from RCM7 and S4 whereas the second set was taken with ADCP. Data were fitted to two different strait flow models. In the first model, the flow resistance is proportional to the flow rate squared. The second model has an additional term accounting for a possible linear relation between flow resistance and flow rate. From the models, it is shown that the linear term is significant in the first dataset but not in the second. It is then proved that the linear term is an artefact caused by non-linear current meter response that, unfortunately, was overlooked in some previous analyses.