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1
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A simple tool for the early prediction of the cyanobacteria Nodularia spumigena bloom biomass in the Gulf of Finland

100%
Lilover M. J., Laanemets J.
Oceanologia
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2006
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tom 48
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nr S
A fuzzy logic model for predicting the maximum biomass of the toxic cyanobacteria Nodularia spumigena bloom in the Gulf of Finland is suggested. The model bloom biomass depends on the phosphate conditions up to 15 June, including the excess phosphate left over after the spring bloom and on the phosphate inputs parameterised by wind mixing and upwelling from 1 May to 15 June. The surface layer temperature, set to vary from 14 to 23◦C, is regarded as a bloom regulating parameter. The model simulations showed that the predicted N. spumigena biomasses differ markedly from year to year and clearly depend on phosphate conditions up to 15 June.
2
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Simulation of nutrient transport from different depths during an upwelling event in the Gulf of Finland

81%
Vali G., Zhurbas V., Laanemets J., Elken J.
Oceanologia
|
2011
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tom 53
|
nr (1-TI)
Numerical simulation experiments with a high-resolution circulation model were carried out to study nutrient transport from different depths to the surface 10-m layer during an upwelling event along the northern coast of the Gulf of Finland in July 1999. The initial nutrient distribution is based on field measurements performed in the north-western part of the Gulf. Wind forcing covering the period of the upwelling along the northern coast was turned through 180◦ to simulate an upwelling along the southern coast. The simulation results showed that the main phosphorus transport to the upper 10-m layer occurred from depths shallower than 30 m for the upwelling events along both the northern and the southern coasts. Nitrogen transport to the upper 10-m layer was the largest from depths of 40–55 m for the upwelling along the northern and 40–65 m for the upwelling along the southern coast. Simulated cumulative volume transports to the upper 10-m layer from different depths showed that the contribution from deeper layers was larger in the case of the upwelling along the southern coast. The reduction of wind stress had a bigger influence on water transport from the deeper layers.
3

Downwelling-related mesoscale motions at the entrance to the Gulf of Finland: observations and diagnosis

81%
Laanemets J., Pavelson J., Lips U., Kononen K.
Oceanological and Hydrobiological Studies
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2005
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tom 34
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nr 2
4
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
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Impact of ship-borne nitrogen deposition on the Gulf of Finland ecosystem: an evaluation

71%
Raudsepp U., Laanemets J., Maljutenko I., Hongisto M., Jalkanen J.-P.
Oceanologia
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2013
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tom 55
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nr 4
5
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
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Flow, waves and water exchange in the Suur Strait, Gulf of Riga, in 2008

61%
Raudsepp U., Laanemets J., Haran G., Alari V., Pavelson J., Kouts T.
Oceanologia
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2011
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tom 53
|
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.
6
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Monitoring the effect of upwelling on the chlorophyll a distribution in the Gulf of Finland (Baltic Sea) using remote sensing and in situ data

61%
Uiboupin R., Laanemets J., Sipelgas L., Raag L., Lips I., Buhhalko N.
Oceanologia
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2012
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tom 54
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nr 3
The spatio-temporal variability of chlorophyl a (Chl a) caused by a sequence of upwelling events in the Gulf of Finland in July–August 2006 was studied using remote sensing data and field measurements. Spatial distributions of sea surface temperature (SST) and Chl a concentration were examined using MODIS and MERIS data respectively. The MERIS data were processed with an algorithm developed by the Free University of Berlin (FUB) for case 2 waters. Evaluation of MERIS Chl a versus in situ Chl a showed good correlation (r2 = 0.67), but the concentration was underestimated. The linear regression for a 2 h window was applied to calibrate MERIS Chl a. The spatio-temporal variability exhibited the clear influence of upwelling events and related filaments on Chl a distribution in the western and central Gulf. The lowest Chl a concentrations were recorded in the upwelled water, especially at the upwelling centres, and the highest concentrations (13 mg m−3) were observed about two weeks after the upwelling peak along the northern coast. The areas along the northern coast of upwelled water (4879 km2) on the SST map, and increased Chl a (5526 km2) two weeks later, were roughly coincident. The effect of upwelling events was weak in the eastern part of the Gulf, where Chl a concentration was relatively consistent throughout this period.
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