Variability of the CO2 Flux on the Water-Atmosphere Interface in the Black Sea Coastal Waters on Various Time Scales in 2010–2014

D. S. Khoruzhii

Marine Hydrophysical Institute, Russian Academy of Sciences, Sevastopol, Russian Federation

e-mail: khoruzhiy@mhi-ras.ru

Abstract

Due to the present tendency to the increased carbon dioxide content in the atmosphere, one of the priorities in hydrochemical research consists in studying the gas exchange in the water-atmosphere system. At that, quantity assessment of the marine areas’ role in the CO2 transport requires taking into account water spatial heterogeneity based on its ability to invade or evacuate carbon dioxide. Represented are the results of estimating intensity and direction of the CO2 flux between the sea and the atmosphere in the Black Sea coastal waters in 2010–2014 executed based on the in situ hydrochemical studies and reanalysis of meteorological data. The results of direct measurements of the CO2 equilibrium partial pressure in the water surface layer and in the atmosphere near-surface layer were used for the first time for calculating the CO2 flux in the Black Sea waters. The results of analysis of the CO2 flux variability on different time scales are represented. The performed calculations show that the CO2 evacuation prevails in a warm season, whereas its invasion – in a cold season. During the off-season transitions, the water area state is close to equilibrium. The timing limits of the seasons are not constant and vary practically each year. Probable reasons of a CO2 flux seasonal variability are considered. Possible role of the abiogenic, biogenic and anthropogenic factors is assessed as a cause of the observed intensity fluctuations of the CO2 exchange between the sea and the atmosphere. It is shown that on the synoptic time scale, the CO2 flux is characterized by a narrower oscillations’ amplitude as compared to its seasonal and inter-annual variability. It is noted that small-scale temporal variability of the CO2 flux is more pronounced during the cold season. The features of the carbon cycle in the Black Sea coastal waters are considered. Possibility of using information on the CO2 flux intensity and direction for assessing the water area ecological state is discussed.

Keywords

CO2 flux, equilibrium partial CO2 pressure, CO2 evaporation, CO2 invasion, seasonal variability of CO2 flux, CO2 flux daily variation, inter-daily variations of CO2 flux, coastal waters, upwelling

Acknowledgements

The author is grateful to the scientist of the Oceanography Department A.V. Garmashov, the leading research engineer of the Shelf Hydrophysics Department S.A. Shutov and the junior scientist of the Sea Biogeochemistry Department E.V. Medvedev for the provided meteorological data, determination of hydrological parameters and general alkalinity during the studies. The investigation is carried out within the framework of the section "The factors and processes determining the present state and evolution of the biogeochemical structure in the Azov-Black Sea basin under the conditions of changing climate and anthropogenic impact" of the theme № 0827-2018-0003 "Fundamental studies of the oceanologic processes conditioning the marine environment state and evolution under the effect of natural and anthropogenic factors based on the observational methods and modeling (code “Oceanological processes”).

Original russian text

Original Russian Text © D. S. Khoruzhii, 2018, published in MORSKOY GIDROFIZICHESKIY ZHURNAL, Vol. 34, Iss. 5, pp. 434–445 (2018)

For citation

Khoruzhy, D.S., 2018. Variability of the CO2 Flux on the Water-Atmosphere Interface in the Black Sea Coastal Waters on Various Time Scales in 2010–2014. Physical Oceanography, [e-journal] 25(5), pp. 401-411. doi:10.22449/1573-160X-2018-5-401-411

DOI

10.22449/1573-160X-2018-5-401-411

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