engleski

The relationship between the atmospheric variability and productivity in the Adriatic Sea area

Interannual variability of the primary production in the middle Adriatic Sea for the period 1961-2002 was examined and correlated to the various atmospheric and oceanographic parameters. The Locally-weighted scatter plot smoothing (LOWESS) method (Cleveland, 1979) and Sequential algorithm for regime shift detection (SARS, Rodinov, 2004) were applied to the primary production mean annual and spring-summer values, revealing the three periods with significantly different mean productivity rate: 1961-1979, 1980-1996 and 1997-2002. Moreover, the period from 1980 to 1996, with the highest primary production, consists of the two distinguished regimes: periods of increasing (1980-1986) and decreasing (1987-1996) primary production. Whereas in the first period the ecosystem was under the influence of warmer and nutrient richer Levantine Intermediate Water (LIW) intrusions into the Adriatic, in the second period, which started with cold winter 1987, the Eastern Mediterranean Transient (EMT) occurred in the Mediterranean. The new circulation regime prevented the LIW intrusions in the Adriatic, causing its reduced productivity. Weak ventilation in the Adriatic was evidenced in the lower than normal sea temperature and oxygen concentrations bellow the thermocline depth. Analysed atmospheric data: air temperature, precipitation, evaporation, air-sea fluxes and the North Atlantic Oscillation (NAO) index showed similar fluctuation pattern as oceanographic data. Changed regime in the ecosystem, observed around 1980s till the end of 1996 can be also associated to the lower than normal precipitation rate, which is connected with more clear days and higher solar radiation input in the sea. Our analysis connected the shifts in primary production with changes in the climate system via changes in the atmosphere and confirmed the hypothesis that atmospheric variability can trigger the ecosystem changes.

climate changes; regime shift; primary production; Adriatic Sea

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