The Barents Sea is one of the “hot spots” of the ocean-atmosphere energy system. Warm water spreads here from the North Atlantic, which causes an increase in turbulent heat exchange between the sea surface and the atmosphere. This process is especially pronounced during strong winds, the frequency of which over the Barents Seas is very high. Much attention is paid to this problem; however, the effect of mesoscale circulations, in particular, orographic winds, on the ocean-atmosphere heat exchange has been studied rather poorly so far. To investigate the influence of Novaya Zemlya bora (which is a frequent and very strong downslope windstorm) on turbulent heat exchange in the eastern Barents Sea, simulation of one late-autumn bora episode was carried out, when the wind gusts reached 45 m/s. A coupled model COAWST including atmosphere model WRF-ARW, ocean model ROMS (with the sea ice) and sea waves model SWAN with a grid spacing of 3 km was used. To distinguish the roles of different processes, both coupled and uncoupled experiments were carried out, as well as an idealized experiment with a flat topography (simulating thus the conditions without bora).
Based on the modeling results, three zones can be distinguished in which turbulent heat fluxes in numerical experiments with coupled models will differ from those in the uncoupled experiment. In a narrow strip near the coast, turbulent fluxes decrease (in some places by 20-30%) due to mixing and cooling (by 1°C in this episode) of the ocean. At a distance of 5-100 km from the coast turbulent fluxes increase (up to 50%) due to the formation of rough steep waves. In the open sea, the effect of coupling on turbulent fluxes is generally small. When averaged over the entire region, the difference in the turbulent heat fluxes between coupled and uncoupled simulations is 3%. In addition to ocean cooling and mixing near the coast, the bora also contributes to the strengthening of the southern coastal current (with a speed of up to 0.9 m/s on the surface). The heat content of the entire water column in the Novaya Zemlya region decreases by an average of 3% during the bora. However, in the experiment with a flat topography, i.e. excluding bora, these heat losses are even greater, 4%. Thus, bora in the considered episode reduces the heat exchange between the ocean and the atmosphere for the whole region (compared to similar conditions in the absence of bora), although heat transfer locally increases in the coastal region. The effect of bora on the ocean does not extend far from the coast. On the contrary, in the experiment without bora, the zone of more intense mixing extends further from the coast.
