Estimates of tidal energy dissipation and diapycnal diffusivity in the Kuril Straits using TOPEX/POSEIDON altimeter data

Abstract

The Kuril Straits separating the Okhotsk Sea from the North Pacific Ocean are representative regions of strong tidal mixing in the world's oceans. In the present study, we first carry out numerical simulation of the barotropic tidal elevation field in the Okhotsk Sea using a horizontally two‐dimensional primitive equation model. It is found that, to reproduce realistic tidal elevations in the Okhotsk Sea, the energy lost by the incoming barotropic tides to internal waves within the Kuril Straits should be taken into account. The numerical experiments show that the model predicted tidal elevations in the Okhotsk Sea best fit the TOPEX/POSEIDON altimeter data when we take into account the baroclinic energy conversion in the Kuril Straits ∼16 GW for the K1 tidal constituent and ∼37 GW for the major four tidal constituents (K1, O1, M2, S2). For this baroclinic energy conversion, diapycnal diffusivity averaged over the whole area of the Kuril Straits is estimated to be ∼8 × 10−4 m2s−1. This value is about 1 order of magnitude less than assumed for the Kuril Straits in previous ocean general circulation models. We offer this study as a warning against using diapycnal diffusivity just as a tuning parameter to reproduce large‐scale phenomena.