Abstract
The impact of tides on the Bay of Biscay dynamics is investigated by means of an ocean model twin-experiment, consisted of two simulations with and without tidal forcing. The study is based on a high-resolution (1/36∘) regional configuration of NEMO (Nucleus for European Modelling of the Ocean) performing one-year simulations. The results highlight the imprint of tides on the thermohaline properties and circulation patterns in three distinct dynamical areas in the model domain: the abyssal plain, the Armorican shelf and the English Channel. When tides are activated, the bottom stress is increased in the shelf areas by about two orders of magnitude with respect to the open ocean, subsequently enhancing vertical mixing and weakening stratification in the bottom boundary layer. The most prominent feature reproduced only when tides are modelled, is the Ushant front near the entrance of the English Channel. Tides appear also to constrain the freshwater transport of rivers from the continental shelf to the open ocean. The spectral analysis revealed that the tidal forcing contributes to the SSH variance at high frequencies near the semidiurnal band and to the open ocean mesoscale and small-scale features in the presence of summer stratification pattern.
Highlights
Tides are a key physical process for understanding and modelling the 3D ocean circulation, especially in shelf seas and near the coast
As an illustration of the tidal forcing applied in the TON simulation, we present in Figure 2 the amplitude and phase of M2 and M4 tidal constituents
The M4 amplitude is more significant over the continental shelf than the abyssal plain, with maximum amplitudes localised in the Armorican shelf and the English Channel (Figure 2b)
Summary
Tides are a key physical process for understanding and modelling the 3D ocean circulation, especially in shelf seas and near the coast. The authors of [5] suggest that the inclusion of tides in global ocean models allows a better representation of processes at regional scales. Barotropic tide models are often used to calibrate observations derived from altimetry missions (see, e.g., in [6]). There are two common approaches to include tides in the ocean model simulations: either with direct simulation or parameterisation. We examine the prospects of the first method through the study of the impact of tides on a regional ocean model from a dynamical point of view
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