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| Titel |
Estuarine circulation reversals and related rapid changes in winter near-bottom oxygen conditions in the Gulf of Finland, Baltic Sea |
| VerfasserIn |
T. Liblik, J. Laanemets, U. Raudsepp, J. Elken, I. Suhhova |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 9, no. 5 ; Nr. 9, no. 5 (2013-10-30), S.917-930 |
| Datensatznummer |
250085249
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| Publikation (Nr.) |
 copernicus.org/os-9-917-2013.pdf |
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| Zusammenfassung |
| 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. |
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