Spatial variability in the drag coefficient and its role in tidal dynamics and energetics, a case study: The surface M 2 tide in the subsystem of the Barents and Kara Seas

Abstract

The QUODDY-4 three-dimensional finite-element hydrostatic model is modified by including a module for the drag coefficient calculated from external determining parameters of the bottom boundary layer (BBL). The modified model is used to evaluate changes in dynamic characteristics (the amplitude and phases of tidal elevations and the maximum barotropic tidal velocity), as well as some components of the barotropic tidal energy budget in the Barents and Kara Seas, induced by the spatial variability in the drag coefficient. It has been shown that the changes in all tidal characteristics, except for the direction of the averaged (over a tidal cycle) horizontal wave transport of barotropic tidal energy, are significant in the sense that they are either greater than the rms absolute vector error or have identical (or near-identical) orders of magnitude when compared to the tidal characteristics themselves. This implies that the concept of a “constant drag coefficient” should be revised.