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

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Author(s): Urmas Raudsepp | Jaan Laanemets | Getli Haran | Victor Alari | Juss Pavelson | Tarmo Kõuts

Journal: Oceanologia
ISSN 0078-3234

Volume: 53;
Issue: 1;
Start page: 35;
Date: 2011;
Original page

Keywords: Flow | Water exchange | Waves | Modelling | Shear velocity | Strait | Baltic Sea

ABSTRACT
Wind, flow and wave measurements were performed in November-December in 2008 in the relatively narrowand shallow Suur Strait connecting the waters of the Väinameri and the Gulf of Riga.During the measurement period wind conditions were extremely variable, including a severe storm on 23 November. The flow speedalong 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 sealevel gradient. The mean and maximum significant wave heights were 0.53 m and 1.6 m respectively. Because of their longer fetch, southerlywinds generated higher waves in the strait than winds from the north. All wave events caused by the stronger southerly windsinduced sediment resuspension, whereas the current-induced shear velocity slightly exceeded the critical value for resuspensiononly when the current speed was 0.4 m s-1. A triple-nested two-dimensional high resolution (100 m in the Suur Strait) circulation model and the SWANwave 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 grossannual outflow of 23 km3 from the Gulf of Riga. The horizontal distribution of wave-induced shear velocityduring the strong southerly wind event indicated large shear velocities and substantial horizontal variability. The shearvelocities were less than the critical value for resuspension in the deep area of the Suur Strait.
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