Ülo Suursaar

Decadal variations in mean and extreme sea level values along the Estonian coast of the Baltic Sea

ABSTRACT This study presents an overview of the Estonian sea level data set obtained from the coastal tide gauges over the period 1842–2005.Variations in the time-series of annual mean sea level, maxima and minima, as well as standard deviations are investigated and their relationships with variations in the North Atlantic Oscillation index are studied. After correcting the sea level series to spatially varying land uplift rates the series display increasing (1.5–2.7 mm yr−1) trends, which in case of Pärnu tide gauge evidently exceed the global sea level rise rate. The increase is larger in winter, which is in accordance with similar seasonal structures of the NAO index trends. The rise in mean sea level, standard deviations and particularly in maxima (3.5–11.2 mm yr−1) could be explained by the local response to the changing regional wind climate. Due to its windward location the sea level variations in the semi-enclosed study area are sensitive to the ongoing intensification of cyclones and prevailing westwinds. In case of the Pärnu Bay, the statistical fit of both the frequency distributions of hourly data and the maximum values distributions for 1923–2005 are inconsistent with the two highest storm surge values of 253 and 275 cm.

Coastal Damages on Saaremaa Island, Estonia, Caused by the Extreme Storm and Flooding on January 9, 2005

Abstract A cyclone known as Gudrun in the Nordic countries developed above the North Atlantic and traveled over the British Isles, Scandinavia, and Finland on January 7–9, 2005. As a result of high initial levels of the Baltic Sea, the fast-traveling cyclone with a favorable trajectory and strong SW–W winds created a record high storm surge (275 cm) in Pärnu, as well as in many other locations along the west Estonian coast. The January storm induced clearly visible changes in the development of shores and the dynamics of beach sediments over almost all of Estonia. The precondition for the profound changes observed from this storm—which has been observed in connection with some previous major storms—was a combination of the absence of protecting ice cover in the sea, relatively high sea level for a long period before the storm, and a very intensive storm surge taking place over the background of the already elevated sea level. Strong storm waves combined with the high sea level caused substantial changes in the coastal geomorphology of depositional shores on Saaremaa Island, Estonia. The most exceptional changes occurred in the areas that were well exposed to the storm winds and wave activity—for instance, in Kelba, where the high rate of erosion (<3000 m3) resulted in the elongation of a spit by 75 m. Our conclusion is that the January 2005 storm caused significantly larger changes to the depositional shores in west Estonia than the cumulative effects of ordinary storms over the preceding 10–15-year period.

Extreme sea level events in the coastal waters of western Estonia

Abstract Extraordinarily low and high sea level events are analysed on the basis of historical data and their mechanisms of occurrence are studied with the 1 km grid size 2D hydrodynamic model in the two almost tideless semi-enclosed sub-basins of the Baltic Sea, the Gulf of Riga and the Vainameri. The sea level is modelled with realistic meteorological forcing and comparison data from 1999 and 2001. Resonance properties of the sub-basins are studied and their possible role in the formation of extraordinary sea level events is discussed. While the extremely low levels (−1.23 m below the mean sea level) in the Estonian coastal waters do not generally originate locally, the high levels (up to 2.53 m above the mean as measured in the Parnu Bay) are short-term and local. They occur in combination with several forcing and morphometrical factors and are localised in the shallow and narrow bays exposed to the direction of the strongest possible storm winds, SW and W. Model simulations show that extremely high and low sea levels in some small bays of western Estonia can exceed the corresponding values in the Parnu Bay.

Past and current climate change

This section describes long-term observed climatic changes in atmospheric parameters. The focus is on surface climate conditions, but changes in atmospheric circulation are discussed as they often are behind climatic variability seen on regional and local scales. For a summary introduction on mean atmospheric states and conditions in the Baltic Sea Basin see Annex 1.2 with sections on the general atmospheric circulation (A.1.2.1), surface air temperature (A.1.2.2), precipitation (A.1.2.3), clouds (A.1.2.4), and global radiation (A.1.2.5).

Recent Change—Sea Level and Wind Waves

This chapter describes observed changes in sea level and wind waves in the Baltic Sea basin over the past 200 years and the main climate drivers of this change. The datasets available for studying these are described in detail. Recent climate change and land uplift are causing changes in sea level. Relative sea level is falling by 8.2 mm year−1 in the Gulf of Bothnia and slightly rising in parts of the southern Baltic Sea. Absolute sea level (ASL) is rising by 1.3–1.8 mm year−1, which is within the range of recent global estimates. The 30-year trends of Baltic Sea tide gauge records tend to increase, but similar or even slightly higher rates were observed around 1900 and 1950. Sea level in the Baltic Sea shows higher values during winter and lower values during spring and this seasonal amplitude increased between 1800 and 2000. The intensity of storm surges (extreme sea levels) may have increased in recent decades in some parts of the Baltic Sea. This may be linked to a long-term shift in storm tracks.

Observation and analysis of coastal changes in the West Estonian Archipelago caused by storm Ulli (Emil) in January 2012

ABSTRACT Tõnisson, H., Suursaar, Ü., Rivis, R., Kont, A. and Orviku, K., 2013. Observation and analysis of coastal changes in the West Estonian Archipelago caused by storm Ulli (Emil) in January 2012. The study analyzes the meteorological parameters, hydrodynamic conditions and coastal changes at three practically tideless locations on Saaremaa Island caused by storm Ulli (sustained wind speed 20 m/s, gusts 28 m/s) which struck the Estonian coast on 4 January 2012. It was the last and the most influential storm of a series of storms which began on November 2011. Wind and sea-level data from nearby meteorological and hydrological stations were used to provide the forcing data for hydrodynamic study. Wave hindcast was performed using a semi-empirical SMB-type wave model. Shorelines, scarp positions and beach profiles were measured in August 2011, and again during each of storm Berit (in November) and storm Ulli (in January). Local storm surge height reached 1 m, significant wave height (Hs) was up to 2.8 m, the combined sea level and Hs reached 3.65 m, and local wave run-up reached 3.2 m during Ulli. At Cape Kiipsaare, recession of the sandy scarp reached 9 m (at the rate of nearly 1m per hour). The loss of sand was approximately 4–5 m3 per 1 m of shoreline. Erosion occurred on the shores exposed to the prevailing wind direction while accumulation was recorded on the leeward side of the spit. Erosion mostly occurred at the elevations between 1–3 m. Although the winter 2011/12 included a series of influential storms, nearly two-thirds of coastal erosion during the winter 2011/2012 was caused by storm Ulli, which featured the highest sea levels.

Multi-scale analysis of wave conditions and coastal changes in the north-eastern Baltic Sea

ABSTRACT Suursaar, Ü., Alari, V., Tõnisson, H., 2014. Multi-scale analysis of wave conditions and coastal changes in the northeastern Baltic Sea. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 223–228, ISSN 0749-0208. Temporal variations of shoreline changes have been analyzed and interpreted in three differently exposed Estonian coastal sections. Using coastline contours that have been recorded frequently over the last twelve years, as well as recently digitized aerial photographs, orthophotos and old topographic maps (some of them dating back to 1900), all overlaid in the Mapinfo software, areal changes over different sub-periods were calculated. To explain the shoreline changes, two different wave modelling approaches were used and mutually compared. Both the BaltAn65+ reanalysis (an ERA-40 refinement) forced SWAN model hindcast (1965–2005) and the point model runs (1966–2012), locally and independently calibrated against extensive wave measurements in these coastal study sites, confirmed specifically higher (and increasing) intensity of coastal processes in the westerly exposed study sites, and a decrease in northerly exposed sites. Some common quasi-periodic cycles with high stage approximately in 1985–1995, and probably also from 2007 can be found. However, the role of a few randomly occurring extreme winter storms (such as in 1967, 2005, 2007 and 2012) was often decisive within the sub-periods.

Natural Development and Human Activities on Saaremaa Island (Estonia) in the Context of Climate Change and Integrated Coastal Zone Management

The coastal zone is a crucial environment that is experiencing pressure from a wide variety of different agents and interests. Many sandy beaches high in recreation value are suffering from increasing erosion, and the shoreline is receding in these areas despite of tectonic land uplift. Sediment deficit is evident in many places. One key problem in recent decades has been a rapid increase in the number of holiday houses built as close as possible to the seashore. Unlike in the Nordic countries, where major coastal settlement expansion took place after WWII, almost the entire coast of Estonia was, until 1991, proclaimed a Soviet border zone in which activities were strongly restricted. A revival in coastal land use and a rapid increase in coastal settlement have occurred over the last 15–20 years. This paper focuses on Climate Change impacts, natural and artificial changes on the coast of Saaremaa Island associated with increasing pressure and conflicting interests. We also examine the advantages and disadvantages of existing legislation regulating land use within the Estonian coastal zone in the context of integrated coastal zone management. The paper ends with an outlook.

Changes on coasts of western Estonia and Russian Gulf of Finland, caused by extreme storm Berit in November 2011

The study is analyzing the meteorological parameters, hydrodynamic conditions and coastal changes caused by extreme storm known as Berit, which travelled across the Baltic Sea from 27th to 29th of November in 2011. Wind speed on West Estonian islands reached to 19,7 m/s (gusts 29 m/s), 20,4 m/s on the northern coast (gusts 27 m/s) and 15 m/s (gusts 20 m/s) on the Russian Gulf of Finland coast. Sea level at Pärnu reached to 110 cm, 142 cm at Narva-Jõesuu and +190 cm near St Petersburg (outside from the Flood Protection Facility). Shorelines, scarp positions and beach profiles were measured at the end of summer in several sites along Estonian coast and Russian Gulf of Finland coast. Two researchers spent the whole duration of the storm in Harilaid Peninsula and recorded changes in shoreline, scarp positions and beach profiles. Wave run-up and sea-levels were also recorded. All the measurements were carried out using DGPS with the accuracy of 1 cm in vertical and horizontal scale. Russian study site was measured a few days after the storm. In order to assess variations in forcing conditions during the storm a wave hindcast was performed using a SMB-type wave model. Calibrated against the field measurements, the model is forced by wind data, and it calculates significant wave parameters for a chosen location. Significant wave height 1.5 km off the Kelba study site was 2.8 m and maximum waves reached to 4.4 m. The first results indicate that 1.5 m high sandy scarp in Cape Kiipsaare receded up to 4 m. The loss of sand was ca 6 m3 per 1 m of shoreline. The speed of recession was around 0.6 m/h during the peak of the storm. The length of gravel-pebble spit at Kelba increased and new gravel ridges in the proximal part reached to 2.8 m. In the Russian part of the eastern Gulf of Finland as a result of storm and flood the scarp up to 2 m high was formed along 15 km of dunes of the northern coast (Komarovo, Repino). It was the first strong erosion event observed after extreme dunes damage during autumn 2006-winter 2007.

Regional Environmental Sensitivity Index (RESI) Classification of Estonian Shoreline (Baltic Sea)

ABSTRACT Aps, R.; Tõnisson, H.; Suursaar, Ü., and Orviku, K, 2016. Regional Environmental Sensitivity Index (RESI) Classification of Estonian Shoreline (Baltic Sea). In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 972 - 976. Coconut Creek (Florida), ISSN 0749-0208. Despite improving navigation safety measures, there is a growing risk of accidental oil spills and associated oil pollution on the Baltic Sea, an area which has been designated as a Particularly Sensitive Sea Area by the International Maritime Organization. Environmental Sensitivity Index (ESI) maps have been an integral component of oil-spill contingency planning and response in the United States since 1979, serving as a quick reference for oil spill responders. The ESI ranks shoreline into 10 classes in relation to sensitivity, natural persistence of oil, and ease of clean-up. Some countries outside the US have adopted the ESI approach to classify their own shorelines for similar oil spill contingency planning, the resulting maps being referred to as Regional Environmental Sensitivity Index (RESI) maps. However, problems arise when applying the classification system. This article highlights the difficulties of applying the standard ESI classification to the Estonian shoreline and suggests a potential RESI classification scheme for Estonia that would divide cliff shores among sensitivity classes 1 and 5, with most of them into class 5, the designation for those that are the most difficult to clean up (mixed sediments on the beach and no access from the land). An Estonian RESI map layers are integrated into the SmartResponse Web - an analytical tool for emergency response and recovery that is used to combine the information related to the accident, development of an oil spill and information on environmental sensitivity of the Baltic Sea shoreline. The SmartResponse Web enables the identification and dynamic assessment of environmental risks as a continuous process for purposes of determining best practices for reducing or even eliminating the risks, and it is used by the Estonian oil spill response authorities for contingency planning, training and in emergency situation.