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Coherent current oscillations and water exchange in the straits of the Gulf of Riga

100%

Talpsepp L.

Oceanologia

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2005

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tom 47

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nr 2

The water exchange processes through the Irbe and Virtsu (Suur) Straits were investigated in 1993–1997 within the framework of a five-year study programme – the Gulf of Riga Project. Simultaneous current measurement data from autonomous mooring stations in both straits were available for the analysis in two periods. In addition to the dominant signals – inertial oscillations in the Virtsu Strait and diurnal oscillations in the Irbe Strait – low-frequency oscillations were found in both straits. During the experiment in July–August 1994, 12–14-day oscillations were observed in both straits: the maximum phase lag in the Virtsu Strait was 1 day. The other important low-frequency periodic component in both straits was 88 hours. In this case, the phase lag in the Virtsu Strait was about 20 hours. In the 1995 experiment in the Irbe Strait, 42-hour oscillations were observed with a phase lag of 10–12 hours. The amplitude was about 30 cm s−1 in both straits. As in Lilover et al. (1998), where the flow regime in the Irbe Strait was observed, we can interpret these oscillations as being wind-generated. The present work shows the existence of these disturbances also in the Virtsu Strait. The 88-hour oscillations observed in July–August 1994 can be interpreted as the first mode of the basin’s eigenoscillations according to the concept of Otsmann et al. (1997) of a basin with two separate outlets. The lowest frequency oscillation with the period of 12–14 days seemed to propagate to the Gulf of Riga from the Baltic Proper, but the generating force could not be established because there was no noticeable variability between depressions and anticyclones during that period. Based on the current measurements, two types of water exchange through the Irbe strait were established: the outflow over the whole cross-section of the strait, and a bidirectional flow with an inflow near the southern shore and increasing inflow in the near-bottom layers and an outflow in the northern part of the strait.

2

Formation and species composition of stormcast beach wrack in the Gulf of Riga, Baltic Sea

84%

Suursaar U., Torn K., Martin G., Herkul K., Kullas T.

Oceanologia

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2014

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tom 56

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nr 4

3

Influence of landfast ice on the hydrography and circulation of the Baltic Sea coastal zone

84%

Merkouriadi I., Lepparanta M.

Oceanologia

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2013

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tom 55

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nr 1

4

Periodic variability of currents induced by topographically trapped waves in the coastal zone in the Gulf of Finland

84%

Talpsepp L.

Oceanologia

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2006

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tom 48

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nr S

The aim of this paper is to examine the water exchange regime between the bays of northern Estonia (Pakri Bay, Ihasalu Bay and Muuga Bay) and the open part of the Gulf of Finland. To this end, the current measurements and CTD-castings performed at the border of the bays and the open part of the Gulf of Finland in summer 1994, 1995–96 and 1997 are analysed. All the current measurements displayed one feature in common: the existence of periodic variability with a current amplitude of between 5 and 25 cm s−1 and a variability period of 3–4 days (68 hours in Pakri Bay, 72 hours in Muuga Bay and 78 hours in Ihasalu Bay). The amplitudes of this variability differed during different time periods of the experiment and in different parts of the southern Gulf of Finland. The hypothesis was propounded that this variability is the result of bottom-trapped waves, as had been found in many other regions of the Baltic Sea (Aitsam & Talpsepp 1982, Talpsepp 1983). To interpret the results of the measurements, a model of bottom-trapped waves for this region was used. This was the short-wave version of Huthnance’s (1978) numerical model of coastal-trapped waves, according to which the wave parameters for the experimental regions were calculated. Comparison of the model and the measurements implies that coastal-trapped waves do exist off the southern coast of the Gulf of Finland.

5

Large halocline variations in the Northern Baltic Proper and associated meso- and basin-scale processes

84%

Elken J., Malkki P., Alenius P., Stipa T.

Oceanologia

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2006

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tom 48

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nr S

The Northern Baltic Proper is a splitting area of the Baltic Sea saline water route towards the two terminal basins – the Gulf of Finland and the Western Gotland Basin. Large halocline variations (vertical isopycnal displacements of more than 20 m, intra-halocline current speeds above 20 cm s−1) appear during and following SW wind events, which rapidly increase the water storage in the Gulf of Finland and reverse the standard estuarine transport, causing an outflow in the lower layers. In the channel of variable topography, basin-scale barotropic flow pulses are converted into baroclinic mesoscale motions such as jet currents, sub-surface eddies and lowfrequency waves. The associated dynamics is analysed by the results from a special mesoscale experiment, routine observations and numerical modelling.

Ograniczanie wyników

5 Oceanologia

2 Talpsepp L.

1 Alenius P.

1 Elken J.

1 Herkul K.

1 Kullas T.

1 Lepparanta M.

1 Malkki P.

1 Martin G.

1 Merkouriadi I.

1 Stipa T.

1 Suursaar U.

1 Torn K.

1 2014

1 2013

2 2006

1 2005

Coherent current oscillations and water exchange in the straits of the Gulf of Riga

Formation and species composition of stormcast beach wrack in the Gulf of Riga, Baltic Sea

Influence of landfast ice on the hydrography and circulation of the Baltic Sea coastal zone

Periodic variability of currents induced by topographically trapped waves in the coastal zone in the Gulf of Finland

Large halocline variations in the Northern Baltic Proper and associated meso- and basin-scale processes