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1
Content available remote The role of the spatial resolution of a three-dimensional hydrodynamic model for marine transport risk assessment
Andrejev O., Soomere T., Sokolov A., Myrberg K.
Oceanologia
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2011
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No. 53 (1-TI)
309-334
EN
The paper addresses the sensitivity of a novel method for quantifying the environmental risks associated with the current-driven transport of adverse impacts released from offshore sources (e.g. ship traffic) with respect to the spatial resolution of the underlying hydrodynamic model. The risk is evaluated as the probability of particles released in different sea areas hitting the coast and in terms of the time after which the hit occurs (particle age) on the basis of a statistical analysis of large sets of 10-day long Lagrangian trajectories calculated for 1987-1991 for the Gulf of Finland, the Baltic Sea. The relevant 2D maps are calculated using the OAAS model with spatial resolutions of 2, 1 and 0.5 nautical miles (nm) and with identical initial, boundary and forcing conditions from the Rossby Centre 3D hydrodynamic model (RCO, Swedish Meteorological and Hydrological Institute). The spatially averaged values of the probability and particle age display hardly any dependence on the resolution. They both reach almost identical stationary levels (0.67-0.69 and ca 5.3 days respectively) after a few years of simulations. Also, the spatial distributions of the relevant fields are qualitatively similar for all resolutions. In contrast, the optimum locations for fairways depend substantially on the resolution, whereas the results for the 2 nm model differ considerably from those obtained using finer-resolution models. It is concluded that eddy-permitting models with a grid step exceeding half the local baroclinic Rossby radius are suitable for a quick check of whether or not any potential gain from this method is feasible, whereas higher-resolution simulations with eddy-resolving models are necessary for detailed planning. The asymptotic values of the average probability and particle age are suggested as an indicator of the potential gain from the method in question and also as a new measure of the vulnerability of the nearshore of water bodies to offshore traffic accidents.
2
Content available remote Spatial patterns of the wave climate in the Baltic Proper and the Gulf of Finland
Soomere T., Räämet A.
Oceanologia
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2011
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No. 53 (1-TI)
335-371
EN
We make an attempt to consolidate results from a number of recent studies into spatial patterns of temporal variations in Baltic Sea wave properties. The analysis is based on historically measured and visually observed wave data, which are compared with the results of numerical hindcasts using both simple fetch-based one-point models and contemporary spectral wave models forced with different wind data sets. The focus is on the eastern regions of the Baltic Sea and the Gulf of Finland for which long-term wave data sets are available. We demonstrate that a large part of the mismatches between long-term changes to wave properties at selected sites can be explained by the rich spatial patterns in changes to the Baltic Sea wave fields that are not resolved by the existing wave observation network. The spatial scales of such patterns in the open sea vary from > 500 km for short-term interannual variations down to about 100 km for long-term changes.
3
Content available remote The progress in knowledge of physical oceanography of the Gulf of Finland: a review for 1997-2007
Soomere T., Myrberg K., Leppäranta M., Nekrasov A.
Oceanologia
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2008
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No. 50 (3)
287-362
EN
The main findings of studies of the physical oceanography of the Gulf of Finland (GoF) during 1997-2007 are reviewed. The aim is to discuss relevant updates published in international peer-reviewed research papers and monographs, bearing in mind that a comprehensive overview of the studies up to the mid-1990s is available (Alenius et al. 1998). We start the discussion with updates on the basic hydrographical and stratification conditions, and progress in the understanding of atmospheric forcing and air-sea interaction. Advances in the knowledge of basin-scale and mesoscale dynamics are summarised next. Progress in circulation and water exchange dynamics has been achieved mostly by means of numerical studies. While the basic properties of circulation patterns in the gulf have been known for a century, new characteristics and tools such as water age, renewal index, and high-resolution simulations have substantially enriched our knowledge of processes in the Gulf of Finland during the last decade. We present the first overview of both status and advances in optical studies in this area. Awareness in this discipline has been significantly improved as a result of in situ measurements. Our understanding of the short- and long-term behaviour of the sea level as well as knowledge of the properties of both naturally and anthropogenically induced surface waves have expanded considerably during these ten years. Developments in understanding the ice conditions of the Gulf of Finland complete the overview, together with a short discussion of the gulf's future, including the response to climate change. Suggestions for future work are outlined.
4
Content available remote Trends and extremes of wave fields in the north-eastern part of the Baltic Proper
Broman B., Hammarklint T., Rannat K., Soomere T., Valdmann A.
Oceanologia
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2006
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No. 48 (S)
165-184
EN
The paper analyses one of the longest contemporary wave measurements in the northern Baltic Sea, performed at Almagrundet 1978-2003. This record contains the roughest instrumentally measured wave conditions (significant wave height = c. 7.8 m) in the northern Baltic Proper until December 2004. The data for the years 1979-95, the period for which the data are the most reliable, show a linear rising trend of 1.8% per annum in the average wave height. The seasonal variation in wave activity follows the variation in wind speed. The monthly mean significant wave height varies from 0.5 m in May-July to 1.3-1.4 m in December-January. No corrections have been made in the analysis to compensate for missing values, for their uneven distribution, or for ice cover.
5
Content available remote The impact of fast ferry traffic on underwater optics and sediment resuspension
Erm A., Soomere T.
Oceanologia
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2006
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No. 48 (S)
283-301
EN
Wake waves produced by fast ferries bring about significant changes in the optical parameters of sea water in the c. 1 m thick near-bottom layer of the coastal areas of Tallinn Bay. The greatest of these changes occur at relatively small depths, but the duration of the influence increases with increasing depth. Rough quantitative estimates suggest that the overall influence of fast ferry traffic in Tallinn Bay may result in an annual loss of the order of several hundred litres of fine sediments from each metre of the coastline.
6
Content available remote Nonlinear ship wake waves as a model of rogue waves and a source of danger to the coastal environment: a review
Soomere T.
Oceanologia
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2006
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No. 48 (S)
185-202
EN
A substantial part of the energy of wake waves from high-speed ships sailing in shallow water is concentrated in nonlinear components which at times have a solitonic nature. Recent results of investigations into solitonic wave interactions within the framework of the Kadomtsev-Petviashvili equation and their implications for rogue wave theory are reviewed. A surface elevation four times as high as the counterparts occurs if the properties of the interacting waves are specifically balanced. The slope of the water surface may increase eightfold. The resulting structure may persist for a long time. Nonlinear wake components may exert a considerable influence on the marine ecosystem in coastal areas .
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