OS Ocean Science OS Ocean Sci. 1812-0792 Copernicus Publications Göttingen, Germany 10.5194/os-6-311-2010 Seasonal variability of the Caspian Sea three-dimensional circulation, sea level and air-sea interaction Ibrayev R. A. 1 2 Özsoy E. 3 Schrum C. 4 Sur H. İ. 5 Institute of Numerical Mathematics, Russian Academy of Sciences, Moscow, Russia P. P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia Institute of Marine Sciences, Middle East Technical University, Erdemli-Mersin, Turkey Geophysical Institute, The University of Bergen, Bergen, Norway Institute of Marine Sciences and Operation, Istanbul University, Istanbul, Turkey 03 03 2010 6 1 311 329 Copyright: © 2010 R. A. Ibrayev et al. 2010 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://os.copernicus.org/articles/6/311/2010/os-6-311-2010.html The full text article is available as a PDF file from https://os.copernicus.org/articles/6/311/2010/os-6-311-2010.pdf

A three-dimensional primitive equation model including sea ice thermodynamics and air-sea interaction is used to study seasonal circulation and water mass variability in the Caspian Sea under the influence of realistic mass, momentum and heat fluxes. River discharges, precipitation, radiation and wind stress are seasonally specified in the model, based on available data sets. The evaporation rate, sensible and latent heat fluxes at the sea surface are computed interactively through an atmospheric boundary layer sub-model, using the ECMWF-ERA15 re-analysis atmospheric data and model generated sea surface temperature. The model successfully simulates sea-level changes and baroclinic circulation/mixing features with forcing specified for a selected year. The results suggest that the seasonal cycle of wind stress is crucial in producing basin circulation. Seasonal cycle of sea surface currents presents three types: cyclonic gyres in December–January; Eckman south-, south-westward drift in February–July embedded by western and eastern southward coastal currents and transition type in August–November. Western and eastern northward sub-surface coastal currents being a result of coastal local dynamics at the same time play an important role in meridional redistribution of water masses. An important part of the work is the simulation of sea surface topography, yielding verifiable results in terms of sea level. The model successfully reproduces sea level variability for four coastal points, where the observed data are available. Analyses of heat and water budgets confirm climatologic estimates of heat and moisture fluxes at the sea surface. Experiments performed with variations in external forcing suggest a sensitive response of the circulation and the water budget to atmospheric and river forcing.

 References Akhverdiev, I. O. and Demin, Y. L.: O structure sinopticheskih techeniy Kaspiiskogo morya v letniy sezon po rezultatam diagnosticheskih raschetov, in: Kaspiiskoe more. Struktura i dinamika vod, edited by: Kosarev, A. N., Nauka, Moscow, USSR, 5–15, 1989. Arpe, K. and Roeckner, E.: Simulation of the hydrological cycle over Europe: Model validation and impacts of increasing greenhouse gases, Adv. Water Resour., 23, 105–119, 1999. Badalov, A. B. and Rzheplinski, D. G.: Modelirovanie dinamiki deyatelnogo sloya Kaspiiskogo morya pod deystviem sinopticheskih atmosfernyh prosessov, in: Modelirovanie gidrofizicheskih prosessov i poley v zamknutyh vodoemah i moryah, Nauka, Moscow, edited by: Sarkisyan, A. S., USSR, 31–51, 1989. Baidin, S. S. and Kosarev, A. N.: Kaspiiskoe more, Gidrologiya a Gidrohimiya, Nauka, Moscow, USSR, 1986. Beron-Vera, F. J., Ochao, J., and Ripa, P.: A note on boundary conditions for salt and freshwater balances, Ocean Model., 1, 111–118, 1999. Bengtsson, L.: Climate modelling and prediction, Achievements and challenges, in: Proceedings of WMO/IOC/ICSU Conference On The WCRP Climate Variability And Predictability Study (CLIVAR), UNESCO, Paris, France, December 1998, 2–4, 1998. Betts, A. K., Ball, J. H., and Viterbo, P.: Basin-scale surface water and energy budgets for the Mississippi from the ECMWF reanalysis, J. Geophys. Res., 104(D16), 19293–19306, 1999. Bondarenko, A. L.: Techeniya Kaspiiskogo morya i formirovanie polya solenosti vod Severnogo Kaspiya, Nauka, Moscow, Russia, 1993. Bortnik, V. N. and Nikonova, R. E.: Vodnyi balans, in: Terziev, Gidrometeorologiya i Gidrohimiya Morey, Vol.6: Kaspiiskoe more, Iss.1: Gidrometeorologicheskie usloviya, edited by: Kosarev, F. S. and Kerimov A. A., Hydrometeoizdat, St. Petersburg, Russia, 211–221, 1992. Csanady, G. T.: Circulation in the Coastal Ocean, D. Reidel Publ. C., 1982. Esbensen, S. K. and Reynolds, R. W.: Estimating monthly averaged air-sea transfers of heat and momentum using bulk aerodynamic method, J. Phys. Ocean., 11, 457–465, 1981. Ibrayev, R. A., Sarkisyan, A. S., and Trukhchev, D. I.: Seasonal variability of the circulation of the Caspian Sea reconstructed from mean multi-year hydrological data, Izvestiya, Atmos. Ocean. Phys., 37(1), 103–111, 2001. Ibrayev, R. A.: Model of enclosed and semi-enclosed sea hydrodynamics, Russ. J. Numer. Anal. M., 16(4), 291–304, 2001. Kamenkovich, V. M.: Osnovy dinamiki okeana, Hydrometeoizdat, Leningrad, USSR, 1973. Kosarev, A. N.: Gidrologiya Kaspiiskogo i Aralskogo morey, Moscow University Press, Moscow, USSR, 1975. Kosarev, A. N. and Tuzhilkin, V. S.: Klimaticheskie termohalinnye polya Kaspiiskogo moray, Moscow University Press, Moscow, Russia, 1995. Kosarev, A. N. and Yablonskaya, E. A.: The Caspian Sea, SPB Academic Publishing, 1994. Launiainen, J. and Vihma, T.: Derivation of turbulent surface fluxes – an iterative flux-profile method allowing arbitrary observing heights, Environ. Softw., 5(3), 113–124, 1990. Lednev, V. A.: Techeniya Severnogo i Srednego Kaspiya, Morskoy Transport, Moscow, USSR, 1943. Martin, P. J.: Simulation of the mixed layer at OWS November and Papa with several models, J. Geophys. Res., 90(C0), 903–916, 1985. Munk, W. H. and Anderson, E. R.: Note on the theory of the thermocline, J. Mar. Res., 7, 276–295, 1948. Panin, G. N.: Isparenie i teploobmen Kaspiiskogo moray, Nauka, Moscow, USSR, 1987. Paulson, E. A. and Simpson, J. J.: Irradiance measurements in the upper ocean, J. Phys. Oceanogr., 7, 952–956, 1977. Rodionov, S. N.: Global and regional climate interaction: The Caspian Sea experience, Ser. Water and Technology Library, Kluwer Academic Publishers, 11, 1994. Roulett, G. and Madec, G.: Salt conservation, free surface, and varying levels: a new formulation for ocean general circulation models, J. Geophys. Res., 105(C10), 23927–23942, 2000. Samoilenko, V. S. and Sachkova, A. I.: Kompleksnye gidrometeorologicheskie atlasy Kaspiiskogo I Aralskogo morey, Hydrometeoizdat, Leningrad, USSR, 1963. Sarkisyan, A. S., Zaripov, B. R., Kosarev, A. N., and Rzheplinski, D. G.: Diagnosticheskie raschety techeniy v Kaspiiskom more, Izvestiya AN, Fizika Atmos. i Okeana, 12(10), 1106–1110, 1976. Schrum, C. and Backhaus, J. O.: Sensitivity of atmosphere-ocean heat exchange and heat content in North Sea and Baltic Sea, A comparitive Assessment, Tellus, 51A, 526–549, 1999. Schrum, C., Staneva, J., Stanev, E., and Ozsoy, E.: Air-sea exchange in the Black Sea estimated from atmospheric analysis for the period 1979–1993, J. Mar. Syst., 31, 3–19, 2001. Stockman, W.: Issledovaniya kinematiki techeniy u zapadnogo berega v sredney chasti Kaspiiskogo moray, Transactions of the Azerbaidjan Scientific-Investigative Fishery station, Baku, USSR, 1, p. 76, 1938. Sur, H. I., Ozsoy, E., and Ibrayev, R.: Satellite – Derived Flow Characteristcs of the Caspian Sea, in: Satellites, Oceanography and Society, edited by: Halpern, D., Elsevier Science B. V., 289–297, 1998. Terziev, F. S., Kosarev, A. N., and Kerimov, A. A.: Gidrometeorologiya i Gidrohimiya Morey, Kaspiiskoe more, Gidrometeorologicheskie usloviya, Hydrometeoizdat, St. Petersburg, Russia, 6, 1, 1992. Timofeev, N. A.: Radiacionnyi regim okeanov, Naukova Dumka, Kiev, USSR, 1983. Trukhchev, D., Kosarev, A., Ivanova, D. and Tuzhilkin, V.: Numerical analysis of the general circulation in the Caspian Sea, Comptes Rendus de l'Academie Bulgare des Sciences, Sofia, 48(10), 35–38, 1995. Tuzhilkin, V. S., Kosarev, A. N., Trukhchev, D. I., and Ivanova, D. P.: Sezonnye osobennosti obchey cirkulyacii vod glubokovodnoy chasti Kaspiiskogo moray, Meteorologiya I Gidrologiya, 1, 91–99, 1997. UNESCO: Seventh Report of the Joint Panel on Oceanographic Tables and Standards, UNESCO Techn. Papers, Mar. Sci., 24(1), 39–54, 1976.