Long-term heat flux variability and winter convection in the Adriatic Sea

Abstract

Calculations of the Adriatic heat fluxes have been carried out. The most appropriate expressions were used assuming that the Adriatic Sea on average loses heat, as shown by some previous studies. Interannual variations of the heat fluxes were analyzed for the period 1989-1999 using the European Centre for Medium-Range Weather Forecasts ERA-40 Reanalysis data set. One of the most relevant issues resulting from the climatological analysis is the presence of an interannual signal and a significant intra-annual variability during the whole period considered. Large year-to-year changes were evidenced, including a net heat gain in some years like in 1994. Interannual yearly heat flux variations largely depend on winter heat losses. Winter convection and dense water formation in the southern Adriatic are directly linked to winter heat loss, although the extent of the vertical mixing is also dependent on the characteristics of the preconditioning period, more specifically of December. Because of mild winter climatic conditions, in some years, winter convection was shown to be completely absent. Separate analyses of the southern and northern Adriatic heat fluxes were carried out as well to see whether the two subbasin fluxes change independently on an interannual timescale. This is especially important considering that the ventilation of the Southern Adriatic Bottom Water takes place through the combined influence of the Northern Adriatic Dense Water and a local vertical convection.