engleski

Climatology of desert dust depoistion in the Adriatic area (Rogoznica Lake)

One of the most abundant atmospheric aerosols is desert dust of which 55 % originates from North Africa (1), and 10 % is transported by air to the Mediterranean (2). It contains nutrients and, when deposited in the sea, a phytoplankton bloom occurs which regulates the balance of CO2 and O2 through photosynthesis. The aim of the study is to investigate for the first time the climatology of desert dust deposition in the Adriatic sea, with an emphasis on Rogoznica Lake. For that purpose, the daily averaged MERRA-2 reanalysis data (3) for dry, wet, and convective deposition and sedimentation in the period 1989-2019 were used. Spatially averaged time series showed that the main maximum of deposition is in spring and the weaker maximum in autumn. The deposition is more pronounced for the central and southern Adriatic, with highest activity in the second decade. The trend is 0.2-0.27 dkg km^-2 yr-1 for the Adriatic and parts, the highest is in winter, over 3 dkg km-2 yr-1. Wet deposition accounts for 63-92 % of total deposition and 75 % of data contains less than 1.5 % of the mass. Intensity classes are defined for the remaining 25 % and each refers to about 30 % of the mass. On average, over 73 days per year is of weak, 14.6 of moderate, and 3.65 of extreme intensity, which varies spatially. For moderate intensity, the highest trend is 4.5 hours in the northern, and slightly negative (<1 h) in the middle and south Adriatic. For extreme intensity, there is an increasing trend everywhere up to 2 hours per year. Lake Rogoznica is a unique, isolated marine system in the central Adriatic (43° 32’ N, 15° 58’ E) with no direct connection to the open sea. Weak connection with the sea exists through cavities in the karst, but the only supply of freshwater to the lake is atmospheric precipitation, which directly affects the salinity of the surface layer. Given the stable seasonal physicochemical stratification (4) and relatively small volume, the lake is proved to be ideal for monitoring desert dust deposition events, by monitoring nutrient concentration in the surface layer (0–2 m). By analyzing the concentration of nutrients in the surface layer of the lake in the period 2000-2012 no correlation with the MERRA-2 deposition series was found, but several significant events of deposition into the lake were observed during water column stratification when an increase in surface layer nutrients and consequent biological activity was observed. Literature: 1. Ginoux, P., J. M. Prospero, T. E. Gill, N. C. Hsu, and M. Zhao (2012), Rev. Geophys., 50, RG3005. 2. Israelevich, P., E. Ganor, P. Alpert, P. Kishcha, and A. Stupp (2012), J. Geophys. Res., 117, D02205. 3. Global Modeling and Assimilation Office (GMAO) (2015), MERRA-2 tavg1_2d_adg_Nx: 2d, 1- Hourly, Time-averaged, Single- Level, Assimilation, AerosolDiagnostics (extended) V5.12.4, Greenbelt, MD, USA, Goddard Earth Sciences Data and Information Services Center (GES DISC), Accessed: [Feb 19. 2020], 10.5067/HM00OHQBHKTP 4. Ciglenečki, I., Ljubešić, Z., Janeković, I. i Batistić, M. (2017.), u: Gulati, R.D., Zadereev, E.S., Degermendzhi, A.G. (ur.). Ecology of Meromictic Lakes. Springer, 228, 125-154.

desert dust ; Adriatic ; Rogoznica lake ; MERRA reanalysis

nije evidentirano