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.
The article discusses the possibility of protecting the shore by disposing of dredged material at shallow depths. An example of a permanently eroded open marine shore segment located south of the Vistula Lagoon inlet (south-eastern part of the Baltic Sea) is considered. This shore segment is permanently caused by downstream erosion due to the moles bordering the entrance to the Vistula Lagoon (Baltiysk Strait) and interrupting longshore sediment transport. Changes of sediment distribution resulting from a demonstration disposal of clean fine sand at depths of seven to nine metres opposite the eroded segment of the shore are examined. A supplementary numerical modelling analysis of sediment transport for different winds showed that the disposed material is transported northward or southward alongshore depending on the wind direction, and almost none of it is stored at the shore slope. The demonstration disposal and numerical modelling results demonstrate that the only way to use the dredged material to protect the eroded shore near the inlet of the Vistula Lagoon is to dispose it directly onto the beach and not into the shallow water nearby.
Abstract. The Curonian Lagoon is the largest coastal lagoon of the Baltic Sea. The Curonian Lagoon is a hypereutrophic water body beset with two major problems: eutrophication and algal blooms. Biological and chemical data for the study of water eutrophication and algal blooms were collected from 4 sampling points in the coastal and off-shore areas at distances of 1 km and 4-5 km from the Curonian Spit during the period from April 2007 to November 2016. The ratio of mineral nitrogen/phosphorus forms created conditions for regular Cyanobacteria hyperblooms during the summer and early autumn. Such blooms are followed by an increase in the concentration of ammonia nitrogen, pH and BOD 5, their values exceeding the threshold limits for fishery water reservoirs. A distinct peak of chlorophyll a concentration was observed in the period of freshwater Cyanobacteria hyperbloom from July to September or October. During the "hyperbloom" of Cyanobacteria, their accumulation and decomposition, which was caused by a constant wind direction, also led to the local oxygen deficit and fish mortality in the coastal zone. Chlorophyll a concentration was always at the level of intensive bloom (10-100 μg/l) and over the period of 6 years (2008, 2010, 2011, 2012, 2014, 2016) it reached the hyperbloom state (above 100 μg/l). Water temperature appeared to be one of the key factors determining seasonal and long-term variability in phytoplankton abundance and, therefore, the level of eutrophication in the Curonian Lagoon.
Formation of the passive continental margin of the Laptev Sea (Laptev Plate), which was part of the Siberian Platform till the Late Cretaceous, was related to the Late Mesozoic–Cenozoic rifting of the Arctic geodepression. The regime of the passive continental margin still continues. The maximum thickness of the deposits of this age seems to exceed 6 km in the northeastern part of the shelf. The hydrocarbon resources of the Late Precambrian–Cenozoic deposits forming the Laptev Plate cover are evaluated. Based on the concept of the similar evolution of the Laptev Plate and Vilyui syneclise, the geochemical characteristics of dispersed organic matter of the coeval deposits of the Vilyui syneclise are used.
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