Decadal variations in wave heights off Cape Kelba, Saaremaa Island, and their relationships with changes in wind climate

Based on wind data from the Vilsandi meteorological station and a 5-month calibration measurement with a bottom-mounted Recording Doppler Current Profiler (RDCP), a semi-empirical hindcast of wave parameters near the quickly developing accumulative Kelba Spit is presented for the period 1966-2006. The significant wave heights with a gross mean value of 0.56 m exhibited some quasiperiodic cycles, with the last high stage in 1980-95 and a decreasing overall trend of $-0.001$ m per year. At the same time, both the frequency and intensity of high wave events showed rising trends, and the mean wave heights during winter (December to February) increased as well. As the study area has the longest fetches in westerly directions, the discussed tendencies in wave conditions are sensitive to regional changes in the wind climate and can be related to a decrease in the local average wind speed on the one hand, but an intensification of westerly winds, storm events and the wintertime NAO index on the other. The roughest wave storms on record were associated with prominent W-storms on 2 November 1969 and 9 January 2005; a few other extreme wind events (e.g. in 1967, 1999, 2001), however, did not yield equally prominent waves

Waves, currents and sea level variations along the Letipea - Sillamäe coastal section of the southern Gulf of Finland

Variations in the hydrodynamic conditions were studied on the basis of 336 days of measurements with a Doppler current profiler. With wave data as a calibration reference, a semi-empirical hindcast of wave parameters is presented in the fetch-limited near-shore area for the period 1966-2008. A resultant 4-6 cm s-1 westward current dominated along the coast. Occasional fast sub-surface westward currents under modest wind forcing, as well as asymmetrical vertical profiles for westward and eastward currents indicated the influence of upwelling-related baroclinic coastal jets. The average frequency of upwelling was estimated at 17%; some of the events were identified in near-homothermic winter conditions on the basis of salinity and multi-layer flow records. While the mean sea level trend at Narva-Jõesuu roughly approximated the global estimates for 1899-2009, the annual maximum sea level increase was 5-8 mm yr-1. Both mean and maximum wave heights declined as a result of decreasing winds from the north

Analysis of wave time series in the Estonian coastal sea in 2003–2014

Statistics of hindcast wave series were studied at eight differently exposed fetch-limited Estonian coastal sea locations (Harilaid, Kihnu, Kõiguste, Matsi, Neugrund, Sundgrund, Suurupi and Letipea). Based on episodic wave measurements obtained with the bottom mounted Recording Doppler Current Profiler in 2006–2014, a model for significant wave height was calibrated separately for those locations; using wind forcing data from Estonian coastal meteorological stations, a set of hourly hindcasts were obtained over the period from September 2003 to December 2014. Fourier analysis of monthly time series with regard to both average wave conditions and high wave events showed a distinct seasonality with specific amplitudes and the phases that differed by about a month between the locations. In addition, spectra of hourly time series indicated diurnal variations (24 and 12 h harmonics) and a consistent background noise following – 5/3 power law between the periods of 2 h and 4 days. Deseasonalized monthly data were used to analyse trends and extreme deviations (wavestorms). The possible trends, being obviously parts of longer variations, were not statistically significant over the studied 11 years. The lists of the most outstanding storms were different depending on the site

Variations in wind velocity components and average air flow properties at Estonian coastal stations in 1966–2021; Sõrve Peninsula case study

Despite considerable differences in local conditions, the average air flow parameters at coastal stations had similar seasonal and interannual patterns. The decreasing trends in average wind speeds were not reliable due to inhomogeneity in the long-term series. Being less sensitive to inhomogeneities, both the zonal and meridional components and the average air flow estimates increased in 1966â2021. The changes in flow direction and in other wind characteristics were better described as quasi-cyclic rather than using a linear trend. In the Sõrve coastal case study, the wind velocity components were separated into opposite subsets, which were one-sidedly analysed by ignoring the other direction. Both westerly and easterly sub-components increased by 0.5 m/s in 2004â2021. Regarding wind-driven coastal processes along the peninsula, the changes in the westerly component, but not in the easterly component, are important on the western coast, and vice versa for the eastern coast. Assuming the potential impacts of winds via waves and currents, the influence of long-term changes in sea ice conditions were considered. Although the forcing load was more than twice as high on the western coast, the relative effect of the âice maskâ was smaller, as ice conditions were milder there. Along the eastern coast of the Sõrve Peninsula, the prevalence of SW-directed forcing can be expected, because the westerly forcing is shaded there by land. The SW-directed flow has strengthened over the study period because of an increase in the easterly and northerly wind speed subset and a decrease in the ice cover on the Gulf of Riga

Storminess-related rhythmic ridge patterns on the coasts of Estonia

Buried or elevated coastal ridges may serve as archives of past variations in sea level and climate conditions. Sometimes such ridges or coastal scarps appear in patterns, particularly on uplifting coasts with adequate sediment supply. Along the seacoasts of Estonia, where relative-to-geoid postglacial uplift can vary between 1.7 and 3.4 mm/yr, at least 27 areas with rhythmic geomorphic patterns have been identified from LiDAR images and elevation data. Such patterns were mainly found on faster emerging and well-exposed, tideless coasts. These are mostly located at heights between 1 and 21 m above sea level, the formation of which corresponds to a period of up to 7500 years. Up to approximately 150 individual ridges were counted on some cross-shore sections. Ten of these ridge patterns that formed less than 4500 years ago were chosen for detailed characterization and analysis in search of possible forcing mechanisms. Among these more closely studied cases, the mean ridge spacing varied between 19 and 28 m. Using land uplift rates from the late Holocene period, the timespans of the corresponding cross sections were calculated. The average temporal periodicity of the ridges was between 23 and 39 years with a gross mean value of 31 years. Considering the regular nature of the ridges, they mostly do not reflect single extreme events, but rather a decadal-scale periodicity in storminess in the region of the Baltic Sea. Although a contribution from some kind of self-organization process is possible, the rhythmicity in ancient coastal ridge patterns is likely linked to quasi-periodic 25−40-year variability, which can be traced to Estonian long-term sea level records and wave hindcasts, as well as in regional storminess data and the North Atlantic Oscillation index

Influence of wind climate changes on the mean sea level and current regime in the coastal waters of west Estonia, Baltic Sea

The response of semi-realistic wind speed increase scenariosto the mean sea level and current regime of semi-enclosed sub-basinsin the Baltic Sea is studied with a 2D hydrodynamic model. Accordingto the model output of spatial mean sea levels, an increase inthe westerly wind component by 2 m s-1 leads, for example,to a mean sea level rise of up to 3 cm in windward locationsin the study area. The sea level change patterns depend on thewind scenario and coastline configuration. The increases in windspeed considered here also lead to enhanced water exchange throughthe straits, strengthening of the basin-scale circulation, enhancementof up- and downwelling, and increased bottom stresses near coasts

Spatio-temporal variations in hydro-physical and -chemical parameters during a major upwelling event off the southern coast of the Gulf of Finland in summer 2006

The objective of the paper is to document and examine the majorupwelling event that occurred along the northern coast of Estoniain August 2006. With a horizontal extension of 360 km, the eventwas caused by persistent easterlies and was noticed by a largenumber of holidaymakers, as it turned the temperature of thecoastal sea to a chilly 5-10&deg;C for about a month. <i>Insitu</i> measurements from an RDCP current profiler revealed an along-windcoastal jet of up to 60 cm s^-1 and a weak near-bottom countercurrent.The depths of the pycnocline and nutricline rose. The maximumdrop in water temperature was 16&deg;C, that of salinitywas 3.6 PSU. Analysis of satellite images confirmed the largeextension and the prominence of the event

Formation and species composition of stormcast beach wrack in the Gulf of Riga, Baltic Sea * The study was supported by the EU Life+project MARMONI ‘Innovative approaches for marine biodiversity monitoring and assessment of conservation status of nature values in the Baltic Sea’, ESF grant No. 8980, Estonian target financed project SF0180104s08 and Institutional research funding IUT2-20 of the Estonian Research Council.

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

Projected Changes in Wave Conditions in the Baltic Sea by the end of 21st Century and the Corresponding Shoreline Changes

The aim of the study is to analyse possible future changes in the Baltic Sea wave conditions and to project coastal changes in six differently exposed Estonian coastal sections resulting from changing wind climates. In the open parts of the Baltic Sea, the SWAN model with 3 NM spatial resolution was used for simulation of wave fields in 1966–2100. Regional climate projection EUR-11 assuming the RCP4.5 greenhouse gas scenario was used as wind forcing. In addition, using a site-dependently calibrated fetch-based wave model, a set of semi-realistic scenario calculations was obtained by modifying the baseline wind input data in order to investigate the reaction of wave climates and coastal developments. For coastal change, past developments in the shoreline and accumulation-erosion areas were tracked using repeated GPS measurements and GIS-overlaid cartographic and photographic material. The projections showed spatially and temporally varying wave fields and a slight overall increase, which corresponds to increased south-westerly winds. Depending on exposition, the wave climates would change differently even within a single semi-enclosed sea. Using the previously established empirical relationships between wave parameters and shoreline changes, we predict that erosion will probably increase in transitional zones while accumulation increases within bays. Sea-level rise and shortening of the sea-ice duration will probably have a remarkable contribution