References

Ocean Science

Ocean Sci.

1812-0792

Copernicus Publications

Göttingen, Germany

10.5194/os-9-917-2013

Estuarine circulation reversals and related rapid changes in winter near-bottom oxygen conditions in the Gulf of Finland, Baltic Sea

Liblik

¹ Laanemets

¹ Raudsepp

¹ Elken

https://orcid.org/0000-0003-3362-2730

¹ Suhhova

Marine Systems Institute, Tallinn University of Technology, Akadeemia Road 15a, 12618 Tallinn, Estonia

30 10 2013

9 5 917 930

2013

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/9/917/2013/os-9-917-2013.html

The full text article is available as a PDF file from https://os.copernicus.org/articles/9/917/2013/os-9-917-2013.pdf

The reversal of estuarine circulation caused by southwesterly wind forcing may lead to vanishing of stratification and subsequently to oxygenation of deep layers during the winter in the Gulf of Finland. Six conductivity, temperature, depth (CTD)+oxygen transects (130 km long, 10 stations) were conducted along the thalweg from the western boundary to the central gulf (21 December 2011–8 May 2012). Two bottom-mounted ADCP were installed, one near the western border and the second in the central gulf. A CTD with a dissolved oxygen sensor was deployed close to the western ADCP. Periods of typical estuarine circulation were characterized by strong stratification, high salinity, hypoxic conditions and inflow to the gulf in the near-bottom layer. Two circulation reversals were observed: one in December–January and one in February. The first reversal event was well developed; it caused the disappearance of the stratification and an increase in the oxygen concentration from hypoxic values to 270 μmol L−1 (to 6 mL L−1) throughout the water column along the thalweg and lasted approximately 1.5 months. Shifts from estuarine circulation to reversed circulation and vice versa were both associated with strong longitudinal (east–west) gulf currents (up to 40 cm s−1) in the deep layer. The change from oxygenated to hypoxic conditions in the western near-entrance area of the gulf occurred very rapidly, within less than a day, due to the intrusion of the hypoxic salt wedge from the NE Baltic Proper. In the eastern part of the gulf, good oxygen conditions caused by reversals remained for a few months.

References 1

Alenius, P., Myrberg, K., and Nekrasov A.: The physical oceanography of the Gulf of Finland: a review, Boreal Environ. Res., 3, 97–125, 1998.

Alenius, P., Nekrasov, A., and Myrberg K.: Variability of the baroclinic Rossby radius in the Gulf of Finland, Cont. Shelf Res., 23, 563–573, 2003.

Almroth, E., Tengberg, A., Andersson, J. H., Pakhomova, S., and Hall P. O. J.: Effects of resuspension on benthic fluxes of oxygen, nutrients, dissolved inorganic carbon, iron and manganese in the Gulf of Finland, Baltic Sea, Cont. Shelf Res., 29, 807–818, 2009.

Bergström, S. and Carlsson, B.: River runoff to the Baltic Sea: 1950–1990, Ambio, 23, 280–287, 1994.

Butterworth, S.: On the theory of filter amplifiers, Experimental Wireless and the Wireless Engineer, 7, 536–541, 1930.

Conley, D. J., Humborg, C., Rahm, L., Savchuk, O. P., and Wulff, F.: Hypoxia in the Baltic Sea and basin-scale changes in phosphorus biogeochemistry, Enviro. Sci. Technol., 36, 5315–5320, 2002.

Conley, D. J.; Björck, S.; Bonsdorff, E.; Carstensen, J.; Destouni, G.; Gustafsson, B. G.; Hietanen, S.; Kortekaas, M.; Kuosa, H.; Meier, H. E. M.; Müller-Karulis, B.; Nordberg, K.; Norkko, A.; Nürnberg, G.; Pitkänen, H.; Rabalais, N. N.; Rosenberg, R.; Savchuk, O. P.; Slomp, C. P.; Voss, M.; Wulff, F.; Zillén, L.: Hypoxia-related processes in the Baltic Sea, Environ. Sci. Technol., 43, 3412–3420, 2009.

Diaz, R. J. and Rosenberg, R.: Spreading Dead Zones and Consequences for Marine Ecosystems, Science, 321, 926–929, <a href="http://dx.doi.org/10.1126/science.1156401">https://doi.org/10.1126/science.1156401</a>, 2008.

Elken, J., Raudsepp, U., and Lips, U.: On the estuarine transport reversal in deep layers of the Gulf of Finland, J. Sea Res., 49, 267–274, 2003.

Elken, J., Mälkki, P., Alenius, P., and Stipa, T.: Large halocline variations in the Northern Baltic Proper and associated meso – and basin-scale processes, Oceanologia, 48, 91–117, 2006.

Elken, J., Raudsepp, U., Laanemets, J., Passenko, J., Maljutenko, I., Pärn, O., and Keevallik, S.: Increased frequency of wintertime stratification collapse events in the Gulf of Finland since the 1990s, J. Marine Syst., <a href="http://dx.doi.org/10.1016/j.jmarsys.2013.04.015">https://doi.org/10.1016/j.jmarsys.2013.04.015</a>, 2013.

Eremina, T. R., Maximov, A. A., and Voloshchuk, E. V.: The influence of climate's variability on the deep-water oxygen conditions in the east of the Gulf of Finland, Oceanology, 52, 771–779, 2012.

Feistel, R., Nausch, G., Matthäus, W., and Hagen, E.: Temporal and Spatial Evolution of the Baltic Deep Water Renewal in Spring 2003, Oceanologia, 45, 623–642, 2003.

Fofonoff, N. P. and Millard, Jr., R. C.: Algorithms for computation of fundamental properties of seawater, Unesco Tech. Pap. Mar. Sci., 44, 1–58, 1983.

Fonselius, S. and Valderrama, J.: One hundred years of hydrographic measurements in the Baltic Sea, J. Sea Res., 49, 229–241, 2003.

Gilbert, D., Sundby, B., Gobeil, C., Mucci, A., and Tremblay, G. H.: A seventy-two-year record of diminishing deep-water oxygen in the St. Lawrence estuary: the northwest Atlantic connection, Limnol. Oceanogr., 50, 1654–1666, 2005.

Haapala, J. and Alenius, P.: Temperature and salinity statistics for the northern Baltic Sea 1961–1990, Finnish Mar. Res., 262, 51–121, 1994.

Håkansson, B., Alenius, P., and Brydsten, L.: Physical environment in the Gulf of Bothnia, Ambio Spec. Rep., 8, 5–12, 1996.

Hansen, D. V. and Rattray, M.: New dimensions in estuary classification, Limnol. Oceanogr., 11, 319–326, 1966.

HELCOM (Helsinki Commission): Eutrophication in the Baltic Sea: an integrated thematic assessment of the effects of nutrient enrichment in the Baltic Sea region, Baltic Sea Environment Proceedings, 115, 2009.

Hietanen, S. and Lukkari, K.: Effects of short-term anoxia on benthic denitrification, nutrient fluxes and phosphorus forms in coastal Baltic sediment, Aquat. Microb. Ecol., 49, 293–302, <a href="http://dx.doi.org/10.3354/ame01146">https://doi.org/10.3354/ame01146</a>, 2007.

Jäntti, H. and Hietanen, H.: The Effects of Hypoxia on Sediment Nitrogen Cycling in the Baltic Sea, AMBIO, 41, 161–169, <a href="http://dx.doi.org/10.1007/s13280-011-0233-6">https://doi.org/10.1007/s13280-011-0233-6</a>, 2012.

Jones, P. D., Jonsson, T., and Wheeler, D.: Extension to the North Atlantic Oscillation using early instrumental pressure observations from Gibraltar and South-West Iceland, Int. J. Climatol., 17, 1433–1450, 1997.

Keevallik, S. and Soomere, T.: Towards quantifying variations in wind parameters across the Gulf of Finland, Est. J. Earth Sci., 59, 288–297, 2010.

Kullenberg, G.: Physical oceanography, in: The Baltic Sea, Elsevier Publishing Company, Amsterdam, 135–182, 1981

Lagemaa, P., Suhhova, I., Nõmm, M., Pavelson, J., and Elken, J.: Comparison of current simulations by the state-of-the-art operational models in the Gulf of Finland, in: IEEE Conference Proceedings, IEEE/OES Baltic 2010 International Symposium, 25–27 August 2010, Riga, Latvia, 1–11, 2010.

Laine, A. O., Andersin, A.-B., Leiniö, S., and Zuur, A. F.: Stratification-induced hypoxia as a structuring factor of macrozoobenthos in the open Gulf of Finland (Baltic Sea), J. Sea Res., 57, 65–77, 2007.

Launiainen, J. and Saarinen, J.: Marine wind characteristics in the northern Baltic Sea, Finnish, Mar. Res., 250, 52–86, 1984.

Li, Y. and Li, M.: Effects of wind on stratification and circulation in a partially mixed estuary, J. Geophys. Res., 116, C12012, <a href="http://dx.doi.org/10.1029/2010JC006893">https://doi.org/10.1029/2010JC006893</a>, 2011.

Liblik, T. and Lips, U.: Characteristics and variability of the vertical thermohaline structure in the Gulf of Finland in summer, Boreal Environ. Res., 16, 73–83, 2011.

Liblik, T. and Lips, U.: Variability of synoptic-scale quasi-stationary thermohaline stratification patterns in the Gulf of Finland in summer 2009, Ocean Sci., 8, 603–614, <a href="http://dx.doi.org/10.5194/os-8-603-2012">https://doi.org/10.5194/os-8-603-2012</a>, 2012.

Lips, I., Lips, U., and Liblik, T.: Consequences of coastal upwelling events on physical and chemical patterns in the central Gulf of Finland (Baltic Sea), Cont. Shelf Res., 29, 1836–1847, 2009.

Lips, U., Lips, I., Liblik, T., and Elken, J.: Estuarine transport versus vertical movement and mixing of water masses in the Gulf of Finland (Baltic Sea), in: IEEE Conference Proceedings, US/EU-Baltic Symposium "Ocean Observations, Ecosystem-Based Management & Forecasting", Tallinn, 27–29 May, 2008, IEEE, 2008, (IEEE Conference Proceedings), 1–8, 2008.

MacCready, P. and Geyer., W. R.: Advances in estuarine physics, Annual Reviews of Marine Science, 2, 35–58, 2010.

Matthäus, W.: Climatic and seasonal variability of oceanological parameters in the Baltic Sea, Beiträge zur Meereskunde, 51, 29–49, 1984.

Matthäus, W. and Lass, H. U.: The recent salt inflow into the Baltic Sea, J. Phys. Oceanogr., 25, 280–286, 1995.

Meccia, V. L., Simionato, C. G., and Guerrero, R. A.: The Rio de la Plata estuary response to wind variability in synoptic timescale: salinity fields and salt wedge structure, J. Coastal Res., 29, 61–77, 2013.

Millero, F. J., Feistel, R., Wright, D. G., and McDoughall, T. J.: The composition of Standard Seawater and the definition of the Reference-Composition Salinity Scale, Deep-Sea Res. Pt. I, 55, 50–72, <a href="http://dx.doi.org/10.1016/j.dsr.2007.10.001">https://doi.org/10.1016/j.dsr.2007.10.001</a>, 2008.

Reissmann, J. H., Burchard, H., Feistel, R., Hagen, E., Lass, H. U., Mohrholz, V., Nausch, G., Umlauf, L., and Wieczorek, G.: Vertical mixing in the Baltic Sea and consequences for eutrophication – A review, Prog. Oceanogr., 82, 47–80, 2009.

Sanay, R. and Valle-Levinson, A.: Wind-induced circulation in semienclosed homogeneous, rotating basins, J. Phys. Oceanogr., 35, 2520–2531, 2005.

Sato, C., Nakayama, K. and Furukawa, K.: Contributions of wind and river effects on DO concentration in Tokyo Bay, Est. Coast. Shelf Sci., 109, 91–97, 2012.

Savchuk, O. P.: Large-scale dynamics of hypoxia in the Baltic Sea, in: Chemical Structure of Pelagic Redox Interfaces: Observation and Modelling, Hdb., Springer Verlag, Berlin Heidelberg, Germany, Env. Chem., 22, 137–160, 2010.

Scully, M. E., Friedrichs, C., and Brubaker, J.: Control of estuarine stratification and mixing by wind-induced straining of the estuarine density field, Estuaries, 28, 321–326, 2005.

Seifert, T., Tauber, F., and Kayser, B.: A high resolution spherical grid topography of the Baltic Sea – 2nd edition, Baltic Sea Science Congress, Stockholm 25–29 November 2001, Poster #147, <a href="www.io-warnemuende.de/iowtopo">www.io-warnemuende.de/iowtopo</a>, 2001.

Simpson, J. H., Brown, J., Matthews, J., and Allen, G.: Tidal straining, density currents, and stirring in the control of estuarine stratification, Estuaries, 13, 125–132, 1990.

Vahtera, E., Conley, D. J., Gustafsson, B. G., Kuosa, H., Pitkänen, H., Savchuk, O. P., Tamminen, T., Viitasalo, M., Voss, M., Wasmund, N., and Wulf, F.: Internal ecosystem feedbacks enhance nitrogen-fixing cyanobacteria blooms and complicate management in the Baltic Sea, Ambio, 36, 186–194, 2007.

Viktorsson, L., Almroth-Rosell, E., Tengberg, A., Vankevich, R., Neelov, I., Isaev, R., Kravtsov, V., and Hall, P. O. J.: Benthic Phosphorus Dynamics in the Gulf of Finland, Aquat. Geochem., 18, 543–564, <a href="http://dx.doi.org/10.1007/s10498-011-9155-y">https://doi.org/10.1007/s10498-011-9155-y</a>, 2012.

Whitney, M. M. and Codiga, D.: Response of a large stratified estuary to wind events: observations, simulations, and theory for Long Island Sound, J. Phys. Oceanogr., 41, 1308–1327, 2011.

Zillén, L., Conley, D. J., Andrén, T., Andrén, E., and Björck, S.: Past occurrences of hypoxia in the Baltic Sea and the role of climate variability, environmental change and human impact, Earth-Sci. Rev., 91, 77–92, 2008.