Fluctuation of temperature in the waters of the open Adriatic

Abstract

       Condensed data on temperature fluctuation in the Adriatic area during the period extending from 1911 till 1914 are given in the present paper.

       It folows from the survey that warmer bodies of water coming from the Mediterranean were flowing into the Adriatic at an increasing rate dining the mentioned period which caused a gradual rising of winter temperature of the Adriatic waters in the open areas, in spite of the very severe winter recorded in the Adriatic area in 1912/1913.

       This occurrence is in good agreement with the Adriatic ingressions which phenomenon was earlier found by the same author while processing the data on salinity fluctuation in the same area, particularly for the period from 1912 till 1914 (Buljan, 1953). The Adriatic ingression is the phenomenon consisting in the rising of salinity of the Adriatic water because of a growing inflow of Mediterranean water into the Adriatic basin.

       As shown by the data given in the present paper, the amplitude of annual temperature fluctuation of the waters of the open Adriatic - including both the South Adriatic Pit and the Jabuka Pit - dwindles when ingressions make their appearance.

      The conclusion can also be drawn now that temperature of the waters of the open and middle Adriatic areas is increasing during the ingression periods.

      It has been established that the amplitudes of variations - both of average and absolute temperatures, and both of minimum and maximum ones - reach higher values in the Jabuka Pit area than in the South Adriatic Pit area. The span between the absolute temperature minima and maxima found in the Jabuka Pit area over a series of years amounted to 15,78°C, while it did not go beyond 14,61°C in the South Adriatic Pit area.

       By pooling of data on the two areas, we find that the common span between the absolute temperature maxima and minima over a series of years reached 16,55°C.

      There is also another phenomenon established by the author, namely that whenever the inflow of Mediterranean water into the Adriatic grows more intense, i.e. with the occurrence of ingressions, the layers where the temperature maxima are found in winter are situated at the sea surface whereas such layers tend to descend whenever the influence of the Mediterranean waters upon the Adriatic basin lessens.

       The sea water layers where the minimum temperature is found in winter shows the opposite behaviour.

       The opinion has been expressed that the vertical convective thermo­haline displacements of water bodies normally play an important part in the Adriatic area during the winter season. It seems, however, that the importance of the advective displacements of water bodies increasing during the periods of ingression in winter in the Adriatic Sea, not only as regards the surface layers, but with respect to the deeper layers of this basin as well.