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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

Currents and waves in the Northern Gulf of Riga: measurement and long-term hindcast

84%

Suursaar U., Kullas T., Aps R.

Oceanologia

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2012

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tom 54

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nr 3

Based on measurements of waves and currents obtained for a period of 302 days with a bottom-mounted RDCP (Recording Doppler Current Profiler) at two differently exposed locations, a model for significant wave height was calibrated separately for those locations; in addition, the Gulf of Riga-Vainameri 2D model was validated, and the hydrodynamic conditions were studied. Using wind forcing data from the Kihnu meteorological station, a set of current, water exchange and wave hindcasts were obtained for the period 1966–2011. Current patterns in the Gulf and in the straits were wind-dependent with characteristic wind switch directions. The Matsi coast was prone to upwelling in persistent northerly wind conditions. During the hindcast period, currents increased along the Koiguste coast and in the Suur Strait, waves decreased noticeably off Koiguste but fluctuated without a clear linear trend near Matsi. The spatially contrasting results for differently exposed coasts were related to the corresponding variations in local wind conditions and to changes in atmospheric circulation patterns over northern Europe.

3

Baltic herring prey selectively on older copepodites of Eurytemora affinis and Limnocalanus macrurus in the Gulf of Riga

84%

Livdane L., Putnis I., Rubene G., Elferts D., Ikauniece A.

Oceanologia

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2016

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tom 58

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nr 1

4

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

5

On the buoyant sub-surface salinity maxima in the Gulf of Riga

84%

Liblik T., Skudra M., Lips U.

Oceanologia

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2017

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tom 59

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nr 2

Thermohaline structure in the Gulf of Riga (GoR) was investigated by a multiplatform measurement campaign in summer 2015. Stratification of the water column was mainly controlled by the temperature while salinity had only a minor contribution. Buoyant salinity maxima with variable strength were observed in the intermediate layer of the Gulf of Riga. The salinity maxima were likely formed by a simultaneous upwelling—downwelling event at the two opposite sides of the Irbe strait. The inflowing salty water did not reach the deeper (> 35 m) parts of the gulf and, therefore, the near-bottom layer of the gulf remained isolated throughout the summer. Thus, the lateral water exchange regime in the near bottom layer of the Gulf of Riga is more complicated than it was thought previously. We suggest that the occurrence of this type of water exchange resulting in a buoyant inflow and lack of lateral transport into the near-bottom layers might contribute to the rapid seasonal oxygen decline in the Gulf of Riga

6

Nutrient turnover at the hypoxic boundary: flux measurements and model representation for the bottom water environment of the Gulf of Riga, Baltic Sea

84%

Eglite E., Lavrinovics A., Muller-Karulis B., Aigars J., Poikane R.

Oceanologia

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2014

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tom 56

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nr 4

7

Characteristics and inter-annual changes in temperature, salinity and density distribution in the Gulf of Riga

84%

Skudra M., Lips U.

Oceanologia

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2017

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tom 59

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nr 1

Available CTD profiles from the Gulf of Riga (May—August, 1993—2012) were analyzed to study inter-annual and long-term changes in temperature, salinity and density in relation to river runoff and atmospheric forcing (e.g. Baltic Sea Index). To describe temporal changes in vertical stratification, the upper mixed layer (UML) and deep layer (DL) parameters were estimated. On average the UML depth increases from 8.7 m in May to 9.0, 11.5 and 13.7 m in June, July and August, respectively, and the UML temperature increases from 8.08C to 12.5, 18.7 and 18.68C (May, June, July and August) while the UML salinity increases from 4.90 g kg1 to 5.14, 5.28 and 5.38 g kg1, respectively. High correlation (r = 0.82) was found between the inter-annual changes in river runoff (spring) and mean salinity in the UML in August as well as between DL mean salinity (r = 0.88) and density (r = 0.84) in the Irbe Strait and DL mean salinity and density in the Gulf of Riga. Inter-annual changes in the UML depth as well as in DL salinity and density had a significant correlation with the changes in Baltic Sea Index. The strongest stratification (August) can be observed in the years with the highest UML temperature and the highest river run-off in spring. We suggest that the predicted increase in water temperature and changes in river run-off due to the climate change would result in faster development of the seasonal thermocline in spring and stronger vertical stratification in summer.

8

Primary productivity in the Gulf of Riga (Baltic Sea) in relation to phytoplankton species and nutrient variability

84%

Purina I., Labucis A., Barda I., Jurgensone I., Aigars J.

Oceanologia

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2018

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tom 60

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nr 4

9

Flow, waves and water exchange in the Suur Strait, Gulf of Riga, in 2008

67%

Raudsepp U., Laanemets J., Haran G., Alari V., Pavelson J., Kouts T.

Oceanologia

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2011

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tom 53

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nr 1

Wind, flow and wave measurements were performed in November–December in 2008 in the relatively narrow and shallow Suur Strait connecting the waters of the V¨ainameri and the Gulf of Riga. During the measurement period wind conditions were extremely variable, including a severe storm on 23 November. The flow speed along the strait varied between ±0.2 m s−1, except for the 0.4 m s−1 that occurred after the storm as a result of the sea level gradient. The mean and maximum significant wave heights were 0.53 m and 1.6 m respectively. Because of their longer fetch, southerly winds generated higher waves in the strait than winds from the north. All wave events caused by the stronger southerly winds induced sediment resuspension, whereas the current-induced shear velocity slightly exceeded the critical value for resuspension only when the current speed was 0.4 m s−1. A triplenested two-dimensional high resolution (100 m in the Suur Strait) circulation model and the SWAN wave model were used to simulate water exchange in 2008 and the wave-induced shear velocity field in the Suur Strait respectively. Circulation model simulations demonstrated that water exchange was highly variable, that cumulative transport followed an evident seasonal cycle, and that there was an gross annual outflow of 23 km3 from the Gulf of Riga. The horizontal distribution of waveinduced shear velocity during the strong southerly wind event indicated large shear velocities and substantial horizontal variability. The shear velocities were less than the critical value for resuspension in the deep area of the Suur Strait.

10

Comparison of heavy metal load in the Gulf of Riga and open Baltic

67%

Seisuma Z., Legzdina M., Kulikova I.

Archiwum Ochrony Środowiska

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1995

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nr 3-4

11

A new predatory cladoceran Cercopagis (Cercopagis) pengoi (Ostroumov 1891) in the Gulf of Gdańsk

67%

Bielecka L., Zmijewska M. I., Szymborska A.

Oceanologia

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2000

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tom 42

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nr 3

Cercopagis pengoi, a species native to the Ponto-Caspian area, was recorded for the first time in the Baltic Sea in the Gulf of Riga and in the open Gulf of Finland in 1992. Sampling in the shallow coastal area of the western part of the Gulf of Gdańsk at weekly intervals between April 1999 and April 2000 revealed the presence of C. pengoi in the zooplankton community. The species was recorded twice, at densities of 1369 indiv. m−3 on 30 July 1999 and 421 indiv. m−3 on 5 August 1999, when the water temperature was at its maximum, in excess of 21.7◦C and 23.9◦C respectively. C. pengoi had never been recorded in the Gulf of Gdańsk prior to 1999.

12

Studies on beached birds and oil pollution in Latvia

59%

Kurochkin A.

The Ring

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1993

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tom 15

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nr 1-2

Ograniczanie wyników

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

Currents and waves in the Northern Gulf of Riga: measurement and long-term hindcast

Baltic herring prey selectively on older copepodites of Eurytemora affinis and Limnocalanus macrurus in the Gulf of Riga

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

On the buoyant sub-surface salinity maxima in the Gulf of Riga

Nutrient turnover at the hypoxic boundary: flux measurements and model representation for the bottom water environment of the Gulf of Riga, Baltic Sea

Characteristics and inter-annual changes in temperature, salinity and density distribution in the Gulf of Riga

Primary productivity in the Gulf of Riga (Baltic Sea) in relation to phytoplankton species and nutrient variability

Flow, waves and water exchange in the Suur Strait, Gulf of Riga, in 2008

Comparison of heavy metal load in the Gulf of Riga and open Baltic

A new predatory cladoceran Cercopagis (Cercopagis) pengoi (Ostroumov 1891) in the Gulf of Gdańsk

Studies on beached birds and oil pollution in Latvia