## 4 Discussion  
Local winds have the predominant influence on water circulation in small, shallow and micro-tidal estuaries and coastal bays. Such influence may lead to complex water circulation patterns due to bathymetric and geometric effects. For instance, [PERSON] [5] has found that geometric constrictions restrict wind-induced circulation, resulting in strong fronts between well-mixed reaches in two small Cape Cod (USA) estuaries. [PERSON] et al. [32] proposed appeared during NW strong wind periods: up-estuary wind weakens and even reverses the shear and reduces the stratification. [PERSON] et al. [33] suggested that wind mixing may dominate over wind straining under typical wind forcing conditions in Chesapeake Bay. More recently, [PERSON] et al. [34] tried to explain the apparent contradiction between these two studies and revealed opposite responses of the upper and lower bay regions to axial winds. Furthermore, [PERSON] et al. [35] have identified substantial transverse variability in Mobile Bay (USA), including the influence of the bathymetric effects previously postulated by [9]. Shallow depths accentuate the wind's influence, sometimes leading to complex water circulation according to observational investigations where the considerable variability of time series is observed [5; 7; 34]. [PERSON] et al. [6] have suggested that the origin of high variability of water currents corresponds to wind variability which is more effective in shallow depths in comparison to deep waters. For instance, the sea breeze represents a sequence covering a wide range of wind directions and intensities. Fangar Bay provides a good example of such estuaries (i.e. shallow and micro-tidal), where the bathymetry and the geometry are relevant, as well as being a small-scale bay, which accentuates the action of the wind. The data analysis conducted here, based on two intensive field campaigns, revealed a differentiated pattern in terms of the function of the location (mouth or inner part of the estuary) and the wind conditions (calm or intense). During calm conditions, estuarine circulation linked with strongly stratified conditions were identified in the mouth, associated with strongly stratified conditions. In the inner part, stratification in the water column also occurred, but water circulation did not show a clear pattern. Mixing in the water column occurs during intense wind with substantial modifications in temperature and salinity profiles as will be analyzed later. Particularly during up-bay wind episodes, outward flow conditions were observed in the mouth. The numerical experiments revealed an axially symmetric transverse structure due to laterally varying bathymetry: up-bay flow occurs in the lateral shoals and down-bay flow in the central channel for up-estuary wind pulses. Consequently, the numerical model's results supported the observed divergence between wind and water flow direction in the center of the mouth in Fangar Bay. This combination of observations and a numerical model confirm that there is a strong transverse  
Figure 12: Barotropic velocities (negative outflow) in the entrance section for selected simulations. variability on water flow when bathymetric effects are considered. Comparing the SIMU 1 and SIMU 2 numerical experiments provides an illustrative example of the influence of bathymetry (see Figure 11). These results are consistent with [PERSON] et al. [36] for a coastal lagoon in the Mediterranean Sea (opposite flow in comparison to wind direction in a central part of the lagoon). Moreover, [PERSON] and [PERSON] [10] and [PERSON] et al. [3] found similar results for large bays than the one cited in this paper, highlighting the value of numerical experiments seeking the fundamental role played by bathymetry in estuarine circulation. Complementing these contributions, we also focused on geometric stretching in the mouth as well as up-bay wind effects using a numerical model in idealized conditions.