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Wave parameters set the base for the design of coastal structures. For this purpose, commonly modelled wave properties are employed. This approach is usually adequate in the open ocean conditions where variations in the wave properties are normally quite limited. The situation is different in the nearshore areas of basins of complicated shape where wave properties can be highly variable. Unfortunately, in many cases, long and sufficiently detailed wave measurements for model validation are not available. The use of default settings of wave models means that possible errors remain unknown. This approach could lead to overdimensioned structures or to structural failures. We address the magnitude of possible errors in such conditions by comparing the output of simple wave models (such as a fetch-based SMB model, the SWAN model forced with one-point homogenous wind, etc.) and a sophisticated multi-nested SWAN wave model forced with ERA-5 winds with recent wave measurements in various nearshore locations in the eastern Baltic Sea. We use records of different length over more than 10 years. While in some locations simple models or models forced with homogenous wind lead to acceptable results, in most areas more sophisticated models are needed to adequately replicate wave properties. The outcome of our analysis provides several site-specific hints for practical coastal engineering.

Analysis and prediction of water level extremes in the eastern Baltic Sea are difficult tasks because of the contribution of various drivers to the water level, the presence of outliers in time series, and possibly non-stationarity of the extremes. Non-stationary modeling of extremes was performed to the block maxima of water level derived from the time series at six locations in the Gulf of Riga and one location in the Baltic proper, Baltic Sea, during 1961–2018. Several parameters of the generalized-extreme-value (GEV) distribution of the measured water level maxima both in the Baltic proper and in the interior of the Gulf of Riga exhibit statistically significant changes over these years. The most considerable changes occur to the shape parameter ξ. All stations in the interior of the Gulf of Riga experienced a regime shift: a drastic abrupt drop in the shape parameter from ξ≈0.03±0.02 to ξ≈-0.36±0.04 around 1986 followed by an increase of a similar magnitude around 1990. This means a sudden switch from a Fréchet distribution to a three-parameter Weibull distribution and back. The period of an abrupt shift (1986–1990) in the shape parameters of GEV distribution in the interior of the Gulf of Riga coincides with the significant weakening of correlation between the water level extremes and the North Atlantic Oscillation (NAO). The water level extremes at Kolka at the entrance to the Gulf of Riga reveal a significant linear trend in shape parameter following the ξ≈-0.44+0.01(t-1961) relation. There is evidence of a different course of the water level extremes in the Baltic proper and the interior of the Gulf of Riga. The described changes may lead to greatly different projections for long-term behavior of water level extremes and their return periods based on data from different intervals. Highlights. Water level extremes in the eastern Baltic Sea and the Gulf of Riga are analyzed for 1961–2018. Significant changes in parameters of generalized-extreme-value distribution are identified. Significant linear trend in shape parameter is established at Kolka. The shape parameter changes in a step-like manner. The shape parameter of GEV has regime shifts around 1986 and 1990 in the gulf.

The phenomenon of wave set-up may substantially contribute to the formation of devastating coastal flooding in certain coastal areas. We study the appearance and properties of empirical probability density distributions of the occurrence of different set-up heights on an approximately 80 km long section of coastline near Tallinn in the Gulf of Finland, eastern Baltic Sea. The study area is often attacked by high waves propagating from various directions, and the typical approach angle of high waves varies considerably along the shore. The distributions in question are approximated by an exponential distribution with a quadratic polynomial as the exponent. Even though different segments of the study area have substantially different wave regimes, the leading term of this polynomial is usually small (between −0.005 and 0.005) and varies insignificantly along the study area. Consequently, the distribution of wave set-up heights substantially deviates from a Rayleigh or Weibull distribution (that usually reflect the distribution of different wave heights). In about three-quarters of the occasions, it is fairly well approximated by a standard exponential distribution. In about 25 % of the coastal segments, it qualitatively matches a Wald (inverse Gaussian) distribution. The Kolmogorov–Smirnov test (D value) indicates that the inverse Gaussian distribution systematically better matches the empirical probability distributions of set-up heights than the Weibull, exponential, or Gaussian distributions.

Monitoring vessel traffic in coastal regions is a key element of maritime security. For this reason, additional ways of detecting moving vessels are explored by using the unique structure of their wake waves based on pressure measurements at the seabed. The experiments are performed at a distance of about 2 km from the sailing line using novel multisensor devices called “hydromasts” that track both pressure and near-bed water flow current velocities. The main tool for the analysis is a windowed Fourier transform that produces a spectrogram of the wake structure. It is shown that time series from the pressure sensors, measured at a frequency of 100 Hz, 0.2 m above the seabed are a valid source of input data for the spectrogram technique. This technique portrays the properties of both divergent and transverse waves with an accuracy and resolution that is sufficient for the evaluation of the speed and distance of the detected vessels from the measurement device. All the detected passings are matched with vessels using automatic identification system (AIS) data. The use of several time series from synchronized multisensor systems substantially suppresses noise and improves the quality of the outcome compared to one-point measurements. Additional information about variations in the water flow in wakes provides a simple and reasonably accurate tool for rapid detection of ship passages.

Coastal environments, in particular heavily populated semi-enclosed marginal seas and coasts like the Baltic Sea region, are stongly affected by human activities. A multitude of human impacts, including climate change, affects the different compartments of the environment, and these effects interact with each other. As part of the Baltic Earth Assessment Reports (BEAR), we present an inventory and discussion of different human-induced factors and processes affecting the environment of the Baltic Sea region, and their interrelations. Some are naturally occurring and modified by human activities (i.e. climate change, coastal processes, hypoxia, acidification, submarine groundwater discharges, marine ecosystems, non-indigenous species, land use and land cover), some are completely human-induced (i.e. agriculture, aquaculture, fisheries, river regulations, offshore wind farms, shipping, chemical contamination, dumped warfare agents, marine litter and microplastics, tourism, coastal management), and they are all interrelated to different degrees. We present a general description and analysis of the state of knowledge on these interrelations. Our main insight is that climate change has an overarching, integrating impact on all of the other factors and can be interpreted as a background effect, which has different implications for the other factors. Impacts on the environment and the human sphere can be roughly allocated to anthropogenic drivers such as food production, energy production, transport, industry and economy. We conclude that a sound management and regulation of human activities must be implemented in order to use and keep the environments and ecosystems of the Baltic Sea region sustainably in a good shape. This must balance the human needs, which exert tremendous pressures on the systems, as humans are the overwhelming driving force for almost all changes we see. The findings from this inventory of available information and analysis of the different factors and their interactions in the Baltic Sea region can largely be transferred to other comparable marginal and coastal seas in the world.

We analyse the impact of ship traffic in the vicinity of navigation channels in a wide shallow waterbody. The crucial hydrodynamic driver in this situation is the depression (Bernoulli) wake that may be transferred into a long-living solitary wave of depression over the shoals. The analysis considers navigation channels in the Venice Lagoon using a new large dataset of approximately 600 measured wake events associated to specific ships whose data are provided by the AIS system. Since the development of the modern industrial port and the opening of the Malamocco–Marghera channel in the late 1960s, growing pressure on the lagoon caused by ship traffic has raised concerns about its physical integrity and habitat survival. The transit of large vessels has been shown to have serious impacts on the shallow water areas adjacent to waterways. Depression wakes created by such vessels can reach significant dimensions (water level dropdown of up to 2.45 m at the channel margin), causing unusually large retreat rates of several sections of the shoreline and which may adversely affect the lagoon morphology. The wakes are analysed in relation to ship and morphological parameters. A formulation is proposed to predict wake amplitude on the basis of ship characteristics and motion.

We analyse a two-step mechanism for the formation of extremely high water levels in a semi-enclosed sub-basin of the Baltic Sea with the pumping of large amounts of water first into this sea and then into the Gulf of Riga. The analysis is based on hourly water level recordings at two observations sites in the gulf (Parnu and Daugavgriva) and at one station (Liepaja) on the eastern shore of the Baltic Sea proper in the period 1961–2017. The empirical distributions of the probability of occurrence of different water levels have a classic quasi-Gaussian shape but are asymmetric: elevated water levels are more likely than negative surges. The highest recorded water levels in the interior of the Gulf of Riga exceed those on the open eastern coasts of the Baltic Sea proper by more than 1 m once in 5–10 years. The time scale of generation and relaxation of such elevated levels is about one day. There is no increase in the magnitude of episodes of strongly elevated water levels in the Gulf of Riga since the 1960s. The annual average number of episodes of significant differences between the water level at Liepaja and Parnu has decreased by a factor of 1.6 whereas differences between Liepaja and Daugavgriva did not change. This pattern of changes indicates an alteration of the directional structure of winds in this area.

We study the evolution of large systems of sticky patches of pollution that float on the sea surface and are moved around by realistic wind and simulated surface currents. The study area is the Gulf of Finland in the eastern Baltic Sea that hosts extremely heavy cargo and tanker traffic. It is assumed that patches merge at collision. Collisions are enhanced by wind impact that depends on the patch size. We implement a space partitioning algorithm for fast simulations of large systems of >8000 patches and perform a series of simulations with different initial size and location of the patches. The resulting empirical distribution of the number of patches of different size is governed universally by a stretched-exponential power law f(x) = A exp (−xb). This indicates that the evolution of large systems of pollution patches on the sea surface exhibits classic self-organization and scale invariance properties. This may be the key effect explaining how the patchiness of waste in marine environment is formed under the impact of different drivers.

Time series of water level at several sites of the eastern Baltic Sea contain statistically almost impossible outliers. Their presence may considerably modify the appearance of the relevant extreme value distributions. We analyse systematically the variation in the parameters of the Generalised Extreme Value (GEV), Gumbel and Weibull distributions for extreme water levels along a 600 km coastal stretch in the north-eastern Baltic Sea. The parameters of the distributions are evaluated using a) three different methods, b) the output of two different ocean models and c) two versions of block maxima (for calendar years and for stormy seasons), and compared with similar parameters retrieved for measured water level time series at five sites. The location and scale parameters of GEV and Gumbel distributions vary smoothly by about ±30% from their average values. The variation is modest along the open shores of the Baltic Sea proper. All these parameters increase almost linearly along the southern coast of the Gulf of Finland. The absolute values of the shape parameter of the GEV distribution are mostly

Wave heights in the Baltic Sea in 1992–2015 have predominantly increased in the sea's western parts. The linear trends in the winter wave heights exhibit a prominent meridional pattern. Using the technique of Empirical Orthogonal Functions (EOF) applied to the multi-mission satellite altimetry data, we link a large part of this increase in the wave heights with the climatic indices of the Scandinavian mode, North Atlantic Oscillation, and Arctic Oscillation. The winter trends show a statistically significant negative correlation (correlation coefficient –0.47±0.19) with the Scandinavian pattern and a positive correlation with the North Atlantic Oscillation (0.31±0.22) and Arctic Oscillation (0.42±0.20). The meridional pattern is associated with more predominant north-westerly and westerly winds driven by the Scandinavian and North Atlantic Oscillation, respectively. All three climatic indices show a statistically significant time-variable correlation with Baltic Sea wave climate during the winter season. When the Scandinavian pattern's influence is strong, North Atlantic and Arctic Oscillations' effect is low and vice versa. The results are backed up by simulations using synthetic data that demonstrate that the percentage of variance retrieved using EOF analysis from the satellite-derived wave measurements is directly related to the percentage of noise in the data and the retrieved spatial patterns are insensitive to the level of noise.

There are a large number of geophysical processes affecting sea level dynamics and coastal erosion in the Baltic Sea region. These processes operate on a large range of spatial and temporal scales and are observed in many other coastal regions worldwide. This, along with the outstanding number of long data records, makes the Baltic Sea a unique laboratory for advancing our knowledge on interactions between processes steering sea level and erosion in a climate change context. Processes contributing to sea level dynamics and coastal erosion in the Baltic Sea include the still ongoing viscoelastic response of the Earth to the last deglaciation, contributions from global and North Atlantic mean sea level changes, or contributions from wind waves affecting erosion and sediment transport along the subsiding southern Baltic Sea coast. Other examples are storm surges, seiches, or meteotsunamis which primarily contribute to sea level extremes. Such processes have undergone considerable variation and change in the past. For example, over approximately the past 50 years, the Baltic absolute (geocentric) mean sea level has risen at a rate slightly larger than the global average. In the northern parts of the Baltic Sea, due to vertical land movements, relative mean sea level has decreased. Sea level extremes are strongly linked to variability and changes in large-scale atmospheric circulation. The patterns and mechanisms contributing to erosion and accretion strongly depend on hydrodynamic conditions and their variability. For large parts of the sedimentary shores of the Baltic Sea, the wave climate and the angle at which the waves approach the nearshore region are the dominant factors, and coastline changes are highly sensitive to even small variations in these driving forces. Consequently, processes contributing to Baltic sea level dynamics and coastline change are expected to vary and to change in the future, leaving their imprint on future Baltic sea level and coastline change and variability. Because of the large number of contributing processes, their relevance for understanding global figures, and the outstanding data availability, global sea level research and research on coastline changes may greatly benefit from research undertaken in the Baltic Sea.

We explore the basic properties of the “climate” of the field of subinertial motions with periods of 2–12 days in the Baltic Sea. The calculations are performed using the output of the Rossby Center Ocean Model RCO with a spatial resolution of 2 nautical miles for 1961–2005. The field of such motions in the Baltic Sea is strongly asymmetric, with much more energy present in the eastern regions of the sea. Spatial distributions of 5-yr average amplitudes of fluctuations of the main and seasonal pycnocline, near-bottom velocity and kinetic and potential energy reflect this asymmetry and also exhibit extensive variability on scales of a few tens of kilometers. The majority of potential energy of such motions is concentrated in a narrow nearshore strip of the sea with a typical width of

Coastal tidal estuaries are vital to the exchange of energy and material between inland waters and the open ocean. Debris originating from the land and ocean enter this environment and are transported by currents (river outflow and tide), wind, waves and density gradients. Understanding and predicting the source and fate of such debris has considerable environmental, economic and visual importance. We show that this issue can be addressed using the Lagrangian coherent structures (LCS) technique which is highly robust to hydrodynamic model uncertainties. Here we present a comprehensive study showing the utility of this approach to describe the fate of floating material in a coastal tidal embayment. An example is given from Moreton Bay, a semi-enclosed subtropical embayment with high morphologic, ecological and economic significance to Southeast Queensland, Australia. Transport barriers visualised by the LCS create pathways and barriers for material transport in the embayment. It was found that the wind field modified both the rate attraction and location of the transport barriers. One of the key outcomes is the demonstration of the significant role of islands in partitioning the transport of material and mixing within the embayment. The distribution of the debris sources along the shoreline are explained by the relative location of the LCS to the shoreline. Therefore, extraction of LCS can help to predict sources and fate of anthropogenic marine debris and thus, serve as a useful way for effective management of vulnerable regions and marine protected areas., 34 pages, 11 figures, In press with Science of the Total Environment

FLAG-ERA FP7/H2020 project FuturICT 2.0 (2017-2020) "Large scale experiments and simulations for the second generation of FuturICT" was aimed to promote collaboration among engineering and social sciences. The Proceedings of Annotations involves the abstracts of articles published by project research groups and indexed in Scopus and/or Web of Science.

This study focuses on time scales and spatial variations of interrelations between average weather conditions and sea surface temperature (SST), and long-term changes in the SST in south-eastern Baltic Sea. The analysis relies on SST samples measured in situ four times a year in up to 17 open sea monitoring stations in Lithuanian waters in 1960–2015. A joint application of non-metric multi-dimensional scaling and cluster analysis reveals four distinct SST regimes and associated sub-regions in the study area. The increase in SST has occurred during both winter and summer seasons in 1960–2015 whereas the switch from relatively warm summer to colder autumn temperatures has been shifted by 4–6 weeks over this time in all sub-regions. The annual average air temperature and SST have increased by 0.03°C yr–1 and 0.02°C yr–1, respectively, from 1960 till 2015. These data are compared with air temperatures measured in coastal meteorological stations and averaged over time intervals from 1 to 9 weeks. Statistically significant positive correlation exists between the SST and the average air temperature. This correlation is strongest for the averaging interval of 35 days.

The wind induced coastal upwelling process often contains a mid-phase that involves coherent long-living cross-shore surface jets of cooler water. These jets extend to 40–45 km from the coast and tend to start from particular coastal locations. We develop a simple method for evaluating the depth in the water column from where the upwelled water originates. We also test the hypothesis that the development of cross-shore surface jets may be triggered by some permanent characteristics such as the bathymetry or the slope of the nearshore seabed. The analysis is performed for a strong and well-documented upwelling in the Gulf of Finland, the Baltic Sea, using high resolution bathymetry data, satellite derived sea surface temperature, surface currents measured by in situ drifters, and properties of water masses in two sampling locations. The results indicate that the cross-shore jets originate exclusively from the shore sections with much steeper slopes (>0.0075) than in the rest of the study area. The cooler water most likely origins from intermediate water masses at depths between 15 and 30 m. The resulting identification of the source depth of the upwelled water and its spatial location assists in understanding the flux of nutrients during upwelling events and their link to the onset of cyanobacteria blooms.

The present study focuses on the quantification of coastal risks associated with erosion and inundation accelerated by sea level rise and extreme storms events in the specific conditions of micro-tidal semi-enclosed seas. The main objective is to develop a measure that characterises climate-related external hazards, the exposure (of people and assets at risk of being damaged) and vulnerability of human and natural systems. This is accomplished by means of adaption of the concept of nondimensional coastal risk (or resilience) index (CRI), as a function of coastal vulnerability and exposure indices, to the conditions of sedimentary shores of the eastern Baltic Sea and testing its suitability for low-lying coastal zones considering their environmental and socio-economic characteristics. The study area is an about 45 km long coastal section of Lithuania in the south-eastern Baltic Sea. We introduce a set of locally relevant coastal vulnerability and exposure variables, apply an Analytical Hierarchy Process to calculate the criteria weights and GIS multi-criteria evaluation approach to calculate the CRI values. The coastal segments with high vulnerability often have low values of the exposure index. About 11% of the study area is under very high risk. The largest CRI values occur at a certain distance from the touristic or industrial spots near Klaipėda, around the Palanga pier and to the north of Sventoji. These coastal sectors are highly populated areas that suffer from sediments deficit due to coastal engineering structures.

Giudici, A.; Kalda, J., and Soomere, T., 2018. Joint Impact of Currents and Winds on the Patch Formation Near the Coasts of the Gulf of Finland. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 1156–1160. Coconut Creek (Florida), ISSN 0749-0208. Both coastal and offshore areas worldwide are greatly affected by the impact of large patches of floating pollution. The main mechanism of clustering of floating litter into patches is the ability of water masses to dive (e.g. during a downwelling event) whereas the litter remains on the surface. This property is quantified in terms of compressibility of the surface velocity field. When this quantity increases over a certain threshold, patchiness of floating litter may increase explosively. However, for quasi-two-dimensional flows such as typical fields of currents over shallow areas, the compressibility is typ...

Delpeche-Ellmann, N. and Soomere, T., 2018. Possible Presence of Shear Instabilities at Steep Slopes during an Upwelling Event in the Gulf of Finland, Baltic Sea. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 481–485. Coconut Creek (Florida), ISSN 0749-0208.The cooler water jets that are present during wind-induced coastal upwellings are known to become unstable after some time and develop into sub-mesoscale phenomena that contribute to the overall mixing. In this study we examine the possibility of vertical shear instabilities, in particular the Kelvin–Helmholtz instability existing in an area where steep bottom slopes are present during an upwelling event in the Gulf of Finland, Baltic Sea. The study utilizes a combination of in-situ sampling stations, satellite derived sea surface temperature (SST) data and the HIROMB model for the Baltic Sea. Examination of the velocity shear and stratification shows that it is possible for the KHI instabilities to exist most popularly at the thalweg section of the study area at a depth of 10–16 m. It is also at this exact location that the cross-shore jets were found to develop into meanders and filaments and the greatest gradient in the SST were observed. Thus these observations signal the possibility of the KHI developing in the vicinity of steep slopes and contributing to the overall mixing.

Kelpsaitė-Rimkienė, L.; Soomere, T.; Bagdanaviciūtė, I.; Nesteckitė, L., and Žalys, M., 2018. Measurements of long waves in Port of Klaipėda, Lithuania. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 761–765. Coconut Creek (Florida), ISSN 0749-0208.Port of Klaipėda is in Klaipėda Strait that connects the Curonian Lagoon with the south-eastern Baltic Sea. Its quays are well sheltered from open sea waves but the port area still hosts dangerous water level oscillations that are apparently generated in the system consisting of the Curonian Lagoon and a strait that connects the lagoon with the Baltic Sea proper. The analysis of spectral composition of these oscillations is based on continuous pressure recordings with a frequency of 4 Hz in Port of Klaipėda during the stormy season December 2016–January 2017. The majority of the energy of oscillations is concentrated in three frequencies bands. Considerable water level changes occurred owing to infragravity motions with periods >30 s ( 0.5 m, were created at lower frequencies. The recording reveals the presence of harbor oscillations with periods 30–200 s (0.005–0.03 Hz) and seiches of the Curonian Lagoon with periods >1200 s (

Kudryavtseva, N.; Pindsoo, K., and Soomere, T., 2018. Application of Non-stationary Extreme Value Modeling to Account for Trends in Extreme Water Level Changes Along the Baltic Sea Coast. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 586–590. Coconut Creek (Florida), ISSN 0749-0208. The classic approach to extreme water levels and their return periods relies on the choice of a convenient extreme value distribution and the subsequent evaluation of its parameters. However, there is increasing evidence that these parameters vary with time owing to climate change. A novel non-stationary modeling of parameters of a generalized extreme value (GEV) distribution is implemented based on the block maximum approach, looking for linear trends in the location parameter of the GEV distribution. The analysis is performed for simulated NEMO-Nordic water level data ...

Coasts worldwide are facing enormous challenges relating to extreme water levels, inundation and coastal erosion. These challenges need to be addressed with consideration given to the need for infrastructure such as for ports and other socio-economic developments, especially for coastal tourism. Choosing the optimal decision support tools (DSTs) for coastal vulnerability and resilience assessment is a major challenge for decision-makers and coastal planners. The robustness and flexibility of coastal decision-making can be improved by using effective DSTs, particularly for the management of coastal hazards. This study provides an overview of the construction and use of decision support systems (DSSs) as combinations of DSTs, such as the commonly used multi-criteria decision analysis (MCDA) methods and an artificial neural network (ANN), integrated with a geographical information system (GIS). The experience of many researchers is that the combination of MCDA techniques based on fuzzy logic, analytical hierarchy process (AHP) and weighted linear combination (WLC), with GIS, and possibly also incorporating ANN, provides decision-makers with a comprehensive tool for efficiently calculating decision support indices (DSIs). Hybrid tools are becoming more popular and relevant among experts due to their multiple functionalities that facilitate decision-making. An integration of DSTs in a DSS and further development of DSIs provides a path for the integration of quantitative and qualitative parameters into the decision-making process, and providing materials to be used in consultation processes. An integrated DSS is more likely to produce high-quality results for decision-makers, handle the uncertainty of analysis, and extend the long-term applicability of tools employed by coastal managers.

Coastal and estuarine ecosystems are heavily influenced through floating debris pollution. This often leads to low-quality coastal water and a negative impact on ecosystem health. The fate of debris, mostly originating from land is impacted by factors including river/tidal currents, winds, waves, and density gradients. The ability to predict hotspots of accumulation of debris has a strong socio-economic importance particularly in efficient debris clean-up operations. We show this can be done using Lagrangian coherent structures (LCSs), a technique highly robust to hydrodynamic model uncertainties. Here we present a comprehensive study showing the utility of this approach to predict areas of spontaneous material accumulation in Moreton Bay, a semi-enclosed subtropical embayment on the southeast Queensland of Australia. The backward finite-time Lyapunov exponent (FTLE) is used as a diagnostic for attracting LCSs, which identifies 11 debris accumulation hotspots. The material accumulation in these identified areas is asymmetric with most events occurring during the ebb tide and most pronounced in the spring tidal cycle, indicating a strong role of outflow in debris accumulation. The impact of wind enhances a high concentration of material accumulation in 8 identified areas of Moreton Bay. Importantly, the identified hotspots, mostly in the vicinity of islands and headland, match the areas in which there is a high level of historical debris collection. This approach thus provides a useful tool for effective clean-up management of vulnerable regions and marine protected areas.

Vessel detection and localization based on wake measurements have been used extensively in aerial and satellite reconnaissance. Here, a wake-based approach for vessel localization and speed estimation is developed using a grid of pressure sensors on the seabed. The sensor array consisted of 9 devices in a 3 × 3 rectangular grid with 2.5 m spacing between the instruments. The array was deployed at a depth of 3 m approximately 2.5 km from the fairway. The pressure time series from all sensors were used to estimate vessel speed and the travelling distance of the wake by interpreting the geometry of its time-frequency representation. The wake direction and an estimate of the vessel course are calculated from the delays of the incoming wake between the sensor locations, equivalently, based on cross-correlations of the signal at neighbouring sensors. Results for single events are compared with data collected from the vessels self-reporting systems (AIS). It is concluded that a grid of pressure sensors can provide a reliable estimation of the vessel location and its speed. The presented technique makes it possible to locate ships, and their speed and course, as the next step towards a vessel traffic monitoring system based on wake recordings.

We analyze the main properties of soliton solutions to the generalized KdV equation u t + [ F ( u ) ] x + u x x x = 0 , where the leading term F ( u ) ∼ q u α , α > 0 , q ∈ R . The far field of such solitons may have three options. For q > 0 and α > 1 the analysis re-confirmed that all traveling solitons have “light” exponentially decaying tails and propagate to the right. If q 0 and α 1 , the traveling solitons (compactons) have a compact support (and thus vanishing tails) and propagate to the left. For more complicated F u and α > 1 (e.g., the Gardner equation) standing algebraic solitons with “heavy” power-law tails may appear. If the leading term of F u is negative, the set of solutions may include wide or table-top solitons (similar to the solutions of the Gardner equation), including algebraic solitons and compactons with any of the three types of tails. The solutions usually have a single-hump structure but if F u represents a higher-order polynomial, the generalized KdV equation may support multi-humped pyramidal solitons.

We explore the possibility to identify areas of intense patch formation from floating items due to systematic convergence of surface velocity fields by means of a visual comparison of Lagrangian Coherent Structures (LCS) and estimates of areas prone to patch formation using the concept of Finite-Time Compressibility (FTC, a generalisation of the notion of time series of divergence). The LCSs are evaluated using the Finite Time Lyapunov Exponent (FTLE) method. The test area is the Gulf of Finland (GoF) in the Baltic Sea. A basin-wide spatial average of backward FTLE is calculated for the GoF for the first time. This measure of the mixing strength displays a clear seasonal pattern. The evaluated backward FTLE features are linked with potential patch formation regions with high FTC levels. It is shown that areas hosting frequent upwelling or downwelling have consistently stronger than average mixing intensity. The combination of both methods, FTC and LCS, has the potential of being a powerful tool to identify the formation of patches of pollution at the sea surface., 25 Pages, 5 Figure, Accepted to be published in the Journal of Marine Systems

We employ in-situ surface drifters and satellite derived sea surface temperature data to examine the impact that an upwelling event may have on mixing and Lagrangian transport of surrounding surface waters. The test area is located near the southern coast of the Gulf of Finland where easterly winds are known to trigger intense coastal upwellings. The analysis is based on the comparison of motions of three drifters that follow the currents in the uppermost layer with a thickness of 2 m with MODIS-based sea surface temperature data and high-quality open sea wind time series. The presence of an upwelling event superseded the classic Ekman-type drift of the surface layer and considerably slowed down the average speed of surface currents in the region affected by the upwelled cold water jet and its filaments. The drifters tended to stay amidst the surrounding surface waters. The properties of mixing were evaluated using the daily rate of temperature change along several transects. The upwelled cooler water largely kept its identity during almost the entire duration of the upwelling event. Intense mixing started at a later stage of the upwelling and continued after the end of the event when the winds that have driven the entire process began to subside.

Even though semi-sheltered sea areas usually have limited wave energy resources, some regions of such basins may still be suitable for wave energy production. We provide a review of the existing wave energy studies in the Baltic Sea basin and discuss specific features and limitations for wave energy production in this water body and possible types of small-scale wave energy converters. We also extend the numerical analysis of wave energy resources in the Baltic Sea to some semi-sheltered nearshore sections that may host large levels of wave energy flux because of a specific combination of the wind regime and geometry of the sea. The test areas are located in the vicinity of the Bay of Gdansk and in the eastern Gulf of Finland. The estimates of wave energy flux rely on numerically reconstructed time series of wave properties with a spatial resolution of 5.5 km along a >200 km long coastal section. The average wave energy resource in the test areas is much lower than at the open eastern Baltic Sea coast. However, several sections of the test regions have wave energy potential comparable to fully-open nearshore areas. The onshore wave energy flux reaches 1.79 kW/m at the coast of the Sambian (Samland) Peninsula and 1.61 kW/m in selected sections of the north-eastern Gulf of Finland. These levels provide reasonable options for local wave energy production.