Abstract
Abstract. The paper documents seasonality, interannual-to-decadal variability, and trends in temperature, salinity, and density over a transect in the shallow northern Adriatic Sea (Mediterranean Sea) between 1979 and 2017. The amplitude of seasonality decreases with depth and is much larger in temperature and density than in salinity. Time series of temperature and salinity are correlated in the surface but not in the bottom layer. Trends in temperature are large (up to 0.6 ∘C over 10 years), significant through the area, and not sensitive to the sampling interval and time series length. In contrast, trends in salinity are largely small and insignificant and depend on the time series length. The warming of the area is more during spring and summer. Such large temperature trends and their spatial variability emphasize the importance of maintaining regular long-term observations for the proper estimation of thermohaline trends and their variability. This is particularly important in regions which are key for driving thermohaline circulation such as the northern Adriatic, with the potential to affect biogeochemical and ecological properties of the whole Adriatic Sea.
Highlights
It is shallow, with depths lower than 80 m and limited dimensions, the northern Adriatic shelf (Fig. 1) has been recognized early as an important area in the Mediterranean, as a number of important ocean processes occur there
The North Adriatic Dense Water (NAdDW) spreads over the deep Adriatic layers as a density current (Artegiani and Salusti, 1987) and ventilates the middle and southern Adriatic depressions (Vilibic, 2003; Bensi et al, 2013)
The Potential density anomalies (PDAs) seasonal variance is affected by both temperature and salinity and is largest in the subsurface layer of the eastern side of the transect (80 %–90 %), while it varies between 60 % and 70 % at the bottom of the western side of the transect
Summary
With depths lower than 80 m and limited dimensions (ca. 150 km × 250 km), the northern Adriatic shelf (Fig. 1) has been recognized early as an important area in the Mediterranean, as a number of important ocean processes occur there. The temperature and salinity trends in the last few decades have been found to be significant in different parts of or in the whole Mediterranean Sea (Shaltout and Omstedt, 2014; Grbec et al, 2018; Pastor et al, 2018; Bengil and Mavruk, 2019) This applies to the surface, but it applies to the deep layers to which warming induced by climate change propagates more slowly (Bethoux et al, 1990; Tsimplis and Baker, 2000; Millot et al, 2006; Cusinato et al, 2018).
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