Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 13 11 2009 10.5194/hess-13-2265-2009 http://www.hydrol-earth-syst-sci.net/13/2265/2009/ http://www.hydrol-earth-syst-sci.net/13/2265/2009/hess-13-2265-2009.html http://www.hydrol-earth-syst-sci.net/13/2265/2009/hess-13-2265-2009.pdf 2265 2271 2009-11-26 Geodynamical processes in the channel connecting the two lobes of the Large Aral Sea E. Roget P. Zavialov V. Khan M. A. Muñiz Environmental Physics Group, Department of Physics, University of Girona, Catalonia, Spain Shirshov Institute of Oceanology, Moscow, Russia Hydrometeorological Research Center of the Russian Federation, Moscow, Russia Reasons for the existence of the channel connecting the two lobes of the present Large Aral Sea are discussed. In situ measurements in 2005 show that differences between the measured depths and those contained in the available digital bathymetry of the lake are considerably different at the channel (7.5±0.9 m, at nine measurement stations along it) and at the northern part of the eastern lobe (1.6±0.3 m, at six stations from the western to the eastern shore). Differences in the misfits observed in the two zones are discussed and thought to be a consequence of the variation of the transversal area of the channel as it enters the eastern lobe, which would affect the flow velocity and thus the strength of the erosion process at the bottom. Field data together with satellite images have been used to modify an original digital bathymetry of the lake and have been implemented into a 3-D hydrodynamical model. A numerical simulation shows that a wind of 12 m/s blowing from the east (112°) generates velocities of up to 45 cm/s in the channel, allowing denser water from the eastern lobe (salinity: 132 g/kg) to flow about 38 km towards the fresher western lobe (salinity: 98 g/kg) in one day. The effect of the inflow on the vertical structure of the western lobe is also illustrated. Although nowadays the channel will be soon a thing of the past, in a more general context, the Aral Sea is presented as an example showing that geomorphologic and geophysical processes, along with hydrological and atmospheric processes, must be taken into account for short-term predictions. Allen, M. R.: Possible or probable?, Nature, Sept 18, 425, 6955, p 242, 2003. Blumberg, A. F. and Mellor, G. L.: A description of a three-dimensional coastal ocean circulation model, in: Three-Dimensional Coastal Ocean Models edited by: Heaps, N., American Geophysical Union, 1–16, 1987. Bortnik, V. N. and Chistyaeva, S. P.: Hydrometeorology and Hydrochemistry of the seas of the USSR, The Aral Sea, Leningrad, Gidrometeoizdat, 7, 194~pp., 1990 (in Russian). Chase, T. N., Pielke, R. A., Knaff, J. A., Kittel, T. G. F., and Eastman, J. L.: A comparison of regional trends in 1979–1997 depth-averaged tropospheric temperatures, Int. J. Climatol., 20, 503–518, 2000. Crétaux, J. F., Kouraev, A. V., Papa, F., Berge-Nguyen, M., Cazenave, A., Aladin, N., and Plotinov, I. S.: Evolution of sea level of the big Aral Sea from satellite altimetry and its implications for water balance, J. Great Lakes Res., 31(4), 520–534, 2005. Crétaux, J. F., Létolle, R., and Calmant, S.: Investigations on Aral Sea Regressions from mirabilite deposits and remote sensing, Aquat. Geochem., 15, 277–291, 2009. Dunn, J. R. and Ridgway, K. R.: Mapping ocean properties in regions of complex topography, Deep-Sea Res. Pt. I, 49, 591–604, 2002. Filina, I. Y., Blankenship, D. D., Thoma, M., Lukin, V. V., Masolov, V. N., and Sen, M. K.: New 3D bathymetry and sediment distribution on Lake Vostok: Implication for pre-glacial origin and numerical modeling of internal processes within the lake, Earth Planet. Sc. Lett., 276, 106–114, 2008. Gökaşan, E., Tur, H., Ecevito\uglu, B., Görüm, T., Türker, A., Tok, B., Ça\uglak, F., Birkan, H., and Şimşek, M.: Evidence and implications of massive erosion along the Strait of Istanbul, Geo-Mar. Lett., 25, 324–342, 2005. Gómez-Gesteira, M., Decastro, M., Prego, R., and Martins, F.: Influence of the Barrie de la Maza dock on the circulation pattern of the Ría of A Coruña (NW-Spain), Sci. Mar., 66(4), 337–346, 2002. Gorelkin, N. E. and Kudyshkin, T. V.: Modern hydrometeorological condition of Aral Sea. General Assembly of European Geosciences Unions, Vienna, Austria, collected abstracts in CD-ROM, 2006. Hasselmann, S.: The WAM model – a third generation ocean wave prediction model, J. Phys. Oceanogr., 18, 1775–1810, 1988. Holcombe, T. L., Warren, J. S, Taylor, L. A., Reid, D. F., and Herdendorf, C. E.: Lakefloor geomorphology of Western Lake Erie, J. Great Lakes Res., 23(2), 190–201, 1997. Khan, V. M., Vilfand, R. M., and Zavialov, P. O.: Long-term variability of air temperature in the Aral sea region, J. Marine Syst., 47(1–4), 25–33, 2004. Khan, V. M. and Holko, L.: Snow cover characteristics in the Aral Sea Basin from different data sources and their relation with river runoff, J. Marine Syst., 76, 254–262, doi:10.1016/j.jmarsys.2008.03.012, 2009. Medina, C. E., Gomez-Enri, J., Alonso, J. J., and Villares, M. P.: Water level fluctuations derived from ENVISAT Radar Altimeter (RA-2) and in-situ measurements in a subtropical waterbody: Lake Izabal (Guatemala), Remote Sens. Environ., 112, 2604–3617, 2008. Micklin, P. P.: Desiccation of the Aral Sea: A water management disaster in the Soviet Union, Science, 241, 1170–1176, 1988. Micklin, P. P.: The Aral Sea crisis, in: Dying and Dead Seas, edited by: Nihoul, J. C. J, Zavialov, P., and Micklin, P. P., Kluwer Academic Publishers, 99–123, 2004. Oberhänsli, H., Boroffka, N., Sorrel, Ph., and Krivonogov, S.: Climate variability during the past 2000~years and past economic and irrigation activities in the Aral Sea basin, Irrig. Drainage Syst., 21, 167–183, 2007. Ressl, R. and Micklin, P.: Morphological changes in the Aral Sea: satellite imagery and water balance model, in: Dying and Dead Seas, edited by: Nihoul, J. C. J., Zavialov, P., and Micklin, P. P., Kluwer Academic Publishers, 77–89, 2004. Roget, E. and Casamitjana, X.: Water exchanges between a coastal lagoon and the sea, International Association of Theoretical and Applied Limnology. Proceedings, ISBN~3-510-54034-4, 24, 92–96 1990. Roget, E., Muñiz, M. A., and Zavialov, P.: Mixing related to internal waves and gyres in the western lobe of the Large Aral Sea, Geophys. Res. Abstr., ISBN~1027-7006, EGU2008-A-07371, 2008. Rubanov, I. V., Ishniyazov, D. P., Baskakova, M. A., and Chistyakov, P. A.: Geology of the Aral Sea, FAN, Tashkent, USSR, 247~pp., 1986 (in Russian). Small, E. E., Sloan, L. C., and Nychka, D.: Changes in surface air temperature caused by desiccation of the Aral Sea, J. Climate, 14(3), 284–299, 2001. Winterbottom, S. J.: Medium and short-term channel planform changes on the Rivers Tay and Tummel, Scotland, Geomorphology, 34, 195–208, 2000. Zavialov, P. O., Arashkevich, A. G., Grabovskiy, A. B., Dikarev, S. N., Dzhalilov, G., Evdokimov, Yu. V., Kudyshkin, T. V., Kurbaniyazov, A. K., Kurbaniyazov, S. K., Matchanov, A. G., Ni, A. A., Sapozhnikov, F. V., and Tomashevskaya, I. G.: Quasi-synoptic field survey in the western and eastern basin of the Aral Sea (October 2005), Oceanology, 46(5), 750–754, 2006. Zavialov, P. O., Kostianoy, A. G., Emelianov, S. V., Ni, A. A., Ishniyazov, D., Khan, V. M., Kudyshkin, T. V.: Hydrographic survey in the dying Aral Sea, Geophys. Res. Lett., 30(13), 1659, doi:10.1029.2003GL017427, 2003. Zavialov, P. O., Ni, A. A., Kudyshkin, T. V., Kurbaniyazov, A. K., and Dikarev, S. N.: Five years of field hydrographic research in the Large Aral Sea (2002–2006), J. Marine Syst., 76(3), 263–275, 2008a. Zavialov, P. O., Ni, A. A., Ishniyazov, D. P., Kudyshkin, T. V., Kurbaniyazov, A. K., and Mukhamedzhanova, D.: Ongoing changes in salt composition and dissolved gases in the Aral Sea, Aquat. Geochem., 15(1–2), 263–275, doi:10.1007/s10498-008-9057-9, 2008b. Zavialov, P. O.: Physical Oceanography of the dying Aral Sea, Springer-Verlag, Berlin, ISBN~3-540-22891-8, 148~pp., 2005.