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1
Content available Case-Study Modelling Analysis of Hydrodynamics in the Nearshore of the Baltic Sea Forced by Extreme Along-shore Wind in the Case of a Cross-shore Obstacle
Sokolov A., Chubarenko B.
Archives of Hydro-Engineering and Environmental Mechanics
|
2018
|
Vol. 65, nr 3
163--176
EN
In the current study we use a three-dimensional model with hydrodynamic and spectral wave modules operating in a coupled mode to simulate the response of currents and wind wave fields to winds of 20–25 m/sec offshore of the protective structure of the Saint Petersburg Flood Prevention Facility Complex. The model was calibrated against field data, which allowed us to obtain a tool describing storm situations in the eastern part of the Gulf of Finland with a satisfactory accuracy. The numerical modeling showed that the protective dam did not have a noticeable effect on the levels of stormsurge, significantwave height, or current speed in areas seaward of the dam. The increase in erosion processes on the southern shore of the easternmost part of the Gulf of Finland in recent past has most probably been related to other factors. We found that if a west or south-west wind of at least 25 m/s blows over the Baltic Sea for at least 16 hours, the level of storm surges seaward of the dam may reach 3 or more meters. An artificial strengthening of the coastline and the creation of shore protection structures are recommended.
2
Content available remote Processes and factors influencing the through-flow of new deepwater in the Bornholm Basin
Stigebrandt A.
Oceanologia
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2017
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No. 59 (1)
69--80
EN
This paper is based on the idea that the hydrographical conditions in the Bornholm Basin, and any other basin, can be understood from knowledge of general hydromechanical principles and basin-specific factors. Published results on the variability of the vertical stratification are shown and discussed. Such analyses demonstrate the residence time of water at different depth levels. Different modes of currents forced by winds and by stratification gradients at open vertical boundaries are presented. Vertical mixing is discussed and published results for the Bornholm Basin are shown. An experiment demonstrates that the diffusive properties of the enclosed basin, i.e. below the sill depth of the Słupsk Furrow, can be computed quite well from the horizontal mean vertical diffusivity obtained from historical hydrographical observations. A published two decades long simulation of the vertical stratification shows that the through flow and modification of new deepwater in the Bornholm Basin can be well described based on existing knowledge regarding crucial hydromechanical processes. It also suggests, indirectly, that there should be a weak anticyclonic circulation above the sill depth, which is supported by current measurements.
3
Content available remote Current observations from a looking down vertical V-ADCP : interaction with winds and tide? The case of Giglio Island (Tyrrhenian Sea, Italy)
Cutroneo L., Ferretti G., Scafidi D., Ardizzone G. D., Vagge G., Capello M.
Oceanologia
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2017
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No. 59 (2)
139--152
EN
In the context of the environmental monitoring of the Concordia wreck removal project, measurements of currents, winds and sea level height were made along the eastern coast of the Giglio Island, Tyrrhenian Sea (Italy), during 2012–2013. The aim of the study was to investigate the effect of atmospheric forcing and periodic sea-level changes on the coastal currents. Normalised Cross-Correlation Function analysis allowed us to correlate these observations. A marked inter-seasonal variability was found in both current and local wind velocity observations but a significant level of correlation between the data was only found during strong wind events. Current and wind directions appeared to be uncorrelated and current measurements showed a predominant NW–SE direction, presumably linked to the shape and orientation of Giglio Island itself. During strong winds from the SSE, current flow was towards the NNW but it suddenly switched from the NNW to the SE at the end of wind events. The results show that, at Giglio Island, currents are principally dominated by the general cyclonic Tyrrhenian circulation, and, secondly, by strong wind events. The sea level had no effects on the current regime.
4
Content available Use of random walk in two-dimensional lattice graphs to describe influence of wind and sea currents on oil slick movement
Guze S., Mazurek J., Smolarek L.
Journal of KONES
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2016
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Vol. 23, No. 2
147--153
EN
The concept of oil slick movement being influenced by wind and sea currents is elementary for the decision model of the distribution of large oil spill emergency control means at sea. The analysis of water area conditions such as wind and sea currents is elementary for the concept of oil slick movement. The article presents the model of oil slick movement under the influence of wind and sea currents. In building the model, random walk in two-dimensional lattice graphs has been used. The movement of oil slick is analysed in two ways. In the paper, the movement of the oil slick is analysed in two ways without wind and focus on surface sea currents and with wind and currents. Case one assumes no wind and focuses on surface sea currents only using random walk in a two-dimensional square grid graph. Case two assumes that wind is in place, so oil slick is moving due to surface sea currents and wind currents. The description of movement in case two is based on a two-dimensional lattice graph, which is a combination of a triangular grid graph and a hexagonal grid graph. The article also describes the basic assumptions of oil slick model: the definition of water area, oil slick and algorithm for rescue action to contain the oil spill. Oil slick movement concept is elementary for the decision model of oil spill control at sea. The model allows estimating the distance of oil slick from coastal areas.
5
Content available remote Formation and species composition of stormcast beach wrack in the Gulf of Riga, Baltic Sea
Suursaar Ű., Torn K., Martin G., Herkül K., Kullas T.
Oceanologia
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2014
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No. 56 (4)
673--695
EN
The aim of the study was to investigate hydrodynamic effects on the formation of beach wrack at three locations in the northern Baltic Sea and to quantify the differences between the composition of species found in the beach wrack and in the neighbouring sea. Hydrodynamic measurements and modelling indicated that the beach wrack was mostly of local origin and that it was formed during high sea level and wave events. Comparison of the methods of beach wrack sampling and seabed sampling (diver, underwater video) demonstrated that beach wrack sampling can be considered an alternative tool for describing the species composition of macrovegetation in near-coastal sea areas. Although the hydrodynamic variability is greater in autumn and more biological material is cast ashore, the similarity between the two sampling methods was higher in spring and summer.
6
Content available remote Influence of landfast ice on the hydrography and circulation of the Baltic Sea coastal zone
Merkouriadi I., Leppäranta M.
Oceanologia
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2013
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No. 55 (1)
147-166
EN
The influence of landfast ice on hydrography and circulation is examined in Santala Bay, adjacent to the Hanko Peninsula, Gulf of Finland. Three-dimensional electromagnetic current meters and conductivity-temperature-depth (CTD) sensors were deployed in winters 1999-2000 and 2000-2001 during the Finnish-Japanese "Hanko 9012" experiment. In each winter, data collection started one month before the initial ice formation and lasted until one month after the ice had melted completely. Temperature and salinity are compared with long-term data from the Tvärminne Zoological Station, also located on the Hanko Peninsula. The water temperature was 2°C less than the long-term average. Ice formation and melting show up in the salinity evolution of the water body, which makes salinity a good indicator of ice formation and breakup in Santala Bay. The circulation under the ice became weaker by almost 1 cm s-1.
7
Content available Wind influence on the formation of nearshore currents in the southern Baltic: mumerical modelling results
Sokolov A., Chubarenko B.
Archives of Hydro-Engineering and Environmental Mechanics
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2012
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Vol. 59, nr 1-2
37-48
EN
A two-dimensional numerical model was used for a simulation of vertical average longshore currents generated by both wind friction and wind-wave action in the nearshore zone. The modelling domain includes the southern part of the Baltic Proper (all boundaries were closed). Wind, uniform in space and varying in time, was the only forcing in the model. The correlation coefficient higher than 0.8 was obtained by model calibration versus the field measurements of currents conducted at the Lubiatowo field station (southern Baltic) during about 1.5 months in 2006. Comparative simulations of total currents including both wind-induced drift and wave components, and of total currents including only a wind-induced drift component, showed that the input of the drift component into currents in the nearshore zone is greater than commonly believed. Wind-induced drift strongly dominates outside the zone of wave transformation, and its input into the total resulting currents remains noticeable even in a zone between the shoreline and the depth of the first wave breaking. Thus, wind-induced drift constitutes up to 50% of the resulting longshore currents for longshore winds and no less than 20% of the longshore component of currents for winds at 45 degrees to the longshore direction.
8
Content available Variability of Hydrodynamic and Lithodynamic Coastal Processes in the East Part of the Gulf of Gdańsk
Ostrowski R., Pruszak Z., Skaja M., Szmytkiewicz M.
Archives of Hydro-Engineering and Environmental Mechanics
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2010
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Vol. 57, nr 2
139-153
EN
The paper presents new findings concerning motion of water and sediment in the coastal zone of the east part of the Gulf of Gdańsk, from the Vistula River mouth at Świbno (Poland) to Cape Taran (Russia, Kaliningrad Oblast). The presented study deals with spatial variability of parameters of hydrodynamic and lithodynamic processes which have been subject to theoretical modelling. For the considered coastal segment, deep-water wave conditions reconstructed for a 44-year period have been analysed and transformed to the nearshore zone. Next, velocities of wave-driven longshore currents for the mean statistical year have been calculated, along with the longshore sediment transport rates. Regarding the net longshore sand motion, its detected direction is from Cape Taran towards the Vistula Spit. Very high annual rates of longshore sediment transport have been obtained for the coastal segment at Sambian Peninsula. These rates decrease considerably along the Vistula Spit, reaching zero at a distance of about one third of the Polish part of the Spit, measured from its root. At this location, the net longshore sediment transport (resulting from net longshore wave-current impact) reverses from westward to eastward.
9
Content available Hydrodynamics and Lithodynamics of Dissipative and Reflective Shores in View of Field Investigations
Ostrowski R., Pruszak Z., Skaja M., Szmytkiewicz M., Trifonova E., Keremedchiev S., Andreeva N.
Archives of Hydro-Engineering and Environmental Mechanics
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2010
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Vol. 57, nr 3-4
199-218
EN
The paper presents a comparative analysis of physical processes occurring at two different coasts, which belong to two different European seas. The first coast under examination comprises the sandy shore nearby Lubiatowo, located at the south Baltic Sea in Poland. The second site is represented by the sandy coast in Shkorpilovtsi, located at the west Black Sea in Bulgaria. Both sites are equipped with field research facilities ensuring extensive and precise in situ investigations. The study is focused on differences and similarities of hydro- and lithodynamics as well as the nearshore morphology between the above coastal zones. The present analysis is based on the results of the field campaigns carried out in recent years at the research facilities in Lubiatowo and Shkorpilovtsi. Considering the way in which wave energy transforms on the cross-shore profile, the sea shore at Lubiatowo is found distinctly dissipative while the shore at RB Shkorpilovtsi has a reflective character. This fact implies some differences in the features of wave-current motion and sediment transport.
10
Wybrane elementy i czynniki ryzyka związanego z prądami błądzącymi przy robotach strzelniczych
Gawor P.
WUG : bezpieczeństwo pracy i ochrona środowiska w górnictwie
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2007
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nr 9/1
26-27
PL
W artykule zdefiniowano elementy i czynniki ryzyka oraz przedstawiono zasady analizy niektórych z nich. Szczególną uwagę zwrócono na elementy zależne od osób organizujących i wykonujących roboty strzelnicze. Przedstawione zasady mogą być wykorzystane w analizie i ocenie ryzyka związanego z wykonywaniem robót strzelniczych w zakładach górniczych.
EN
Elements and factors of hazards associated with shooting works are defined and analyzed, with special focus on the elements dependent on the staff organizing and performing shooting works. Principles applicable to the analysis and assessment of the hazards associated with the shooting works conducted in coal companies are presented.
11
Content available remote Periodic variability of currents induced by topographically trapped waves in the coastal zone in the Gulf of Finland
Talpsepp L.
Oceanologia
|
2006
|
No. 48 (S)
75-90
EN
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.
12
Content available remote Large halocline variations in the Northern Baltic Proper and associated meso- and basin-scale processes
Elken J., Mälkki P., Alenius P., Stipa T.
Oceanologia
|
2006
|
No. 48 (S)
91-117
EN
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 low-frequency waves. The associated dynamics is analysed by the results from a special mesoscale experiment, routine observations and numerical modelling.
13
Content available remote Coherent current oscillations and water exchange in the straits of the Gulf of Riga
Talpsepp L.
Oceanologia
|
2005
|
No. 47 (2)
115-127
EN
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 -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.
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