Hannes Tõnisson - Academia.edu (original) (raw)

Papers by Hannes Tõnisson

Baltica

A diverse suite of erosional features along the shoreline of Lehtma (Hiiumaa Island, Estonia) is ... more A diverse suite of erosional features along the shoreline of Lehtma (Hiiumaa Island, Estonia) is used to assess their morphodynamic context and preservation potential. The Holocene strandplain along the east-facing (leeward) shoreline has experienced rapid retreat due to the anthropogenically induced sediment deficit. The study site is located just updrift of the erosional-depositional fulcrum segment, with southerly longshore transport resulting in the accumulation of eroded sand along a drift-aligned spit. The most prominent erosional indicators are mature pine trees in different stages of undercutting, toppling, fragmentation, and burial. Morphological features include scarps in paleo-beach/dune ridges (height: > 1 m), as well as modern berm scarps. Mineralogical indicators are exemplified by heavy-mineral concentrations (HMCs) of variable thickness (some > 2 cm) and concentration. Representative samples show a substantial increase in bulk low-field magnetic susceptibility ...

This overview compares various environmental publications to find out the contrasts and similarit... more This overview compares various environmental publications to find out the contrasts and similarities in climatic conditions in the last 6000 years in Estonia and Svalbard.Both regions with their geographical differences are sensitive to climate change, Estonia on the meeting borderline with maritime and continental air masses and Svalbard at the end of the North Atlantic Cyclone track with very changeable climatic conditions. The study aims to find out how the colder and warmer periods differ in the larger time scale such as the Middle and Late Holocene.The Holocene in Estonia and Svalbard experienced dramatic climate changes including several cold and warm episodes. A variation of paleoclimatic records was compared with other geological proxies (lake sediments, glaciers, pollen, coastal and dune belt formation data presented in scientific publications) and a good correspondence between cold and warm climate periods was found in both areas. The climate conditions were warm and dry ...

Journal of Marine Science and Engineering

Coastal archives of changing hydrometeorological conditions include mineralogical anomalies, such... more Coastal archives of changing hydrometeorological conditions include mineralogical anomalies, such as heavy-mineral concentrations (HMCs) of variable thickness and intensity, which contain varying ferrimagnetic (e.g., magnetite) fractions. As an effective alternative to laborious mineralogical and granulometric analysis, we present the first set of bulk-volume low-field magnetic susceptibility (MS) databases from beach and dune lithosomes in the Western Estonian archipelago: Harilaid cuspate foreland (westernmost Saaremaa Island) and Tahkuna strandplain (northernmost Hiiumaa Island). Readings were conducted both in situ from trench walls and on core subsamples. At the Tahkuna site, late Holocene beach ridges reveal substantially lower values: quartz-dominated dune sequences grade from 5–20 μSI downward to diamagnetically dominated (−1–7 μSI) beach facies. Values are higher (20–140 μSI) in historically reactivated parabolic dunes that are encroaching southward over the strandplain. At...

EGU General Assembly Conference Abstracts, Apr 1, 2019

EGU General Assembly Conference Abstracts, Apr 1, 2017

Estonian Journal of Earth Sciences, 2017

Buried or elevated coastal ridges may serve as archives of past variations in sea level and clima... more 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.

Routledge eBooks, Mar 5, 2013

in 1990. 4 The Lithuanian émigré Vytautas Kavolis described intellectual culture as follows: "Int... more in 1990. 4 The Lithuanian émigré Vytautas Kavolis described intellectual culture as follows: "Intellectual cultures are traditions of unceasing concern with ideas of universal human significance. Intellectuals are individuals who participate intensely in these traditions. [...] A restricted mode of thought that does not transcend the limits of a particular field of specialization [...] does not belong to intellectual culture..." According to the scholar, the "intellectual … not only judges that which exists but also develops alternatives (political, scientific, or artistic) to that which in his surroundings is thought to be 'reality'." Kavolis, "On the Deformations of Intellectual Culture," 34-35. This definition of intellectual culture corresponds with conceptions of cultural opposition discussed earlier in this chapter. 5 Grinius, "Literature and the Arts in Captive Lithuania," 197-214. 6 Vardys, "The Role of Churches," 151-64. 7 Misiūnas and Taagepera, The Baltic States. 8 Kasekamp, A History of the Baltic States, X.

Encyclopedia of the World's Coastal Landforms, …, 2010

As a result of rapid coastal zone urbanization, many sand dunes in Europe are currently at risk o... more As a result of rapid coastal zone urbanization, many sand dunes in Europe are currently at risk of degradation by their overuse, misuse or poor management. In this context, using examples from the coastal zones in Bulgaria and Estonia, the present paper is designed to illustrate and analyze critical problems of dune destruction caused by expanding human impact. Sand beaches and associated dune systems are under increasing pressure as the population along the coastlines of both countries is continuously growing. The primary focus of the study is to assess the current state of dunes in the subject countries and to identify the leading human-induced threats to the natural dune systems. Two case study sites were selected: an area around the Sunny Beach Resort and the Nessebar Peninsula, on the southern Bulgarian coast, and an area of Võsu Resort on the southern coast of the Gulf of Finland, northern Estonia. Available data from field surveys, topographic maps, aerial photographs and orthophotos taken at different times were used in order to identify changes in dune landscape. Data processing and analysis were performed in GIS environment. Despite different types of sand dunes and different management measures along the Bulgarian and Estonian coastlines, the results obtained clearly show irreversible alterations to the dune areas and human-induced reduction of the area of dune landscape in general. Nevertheless, the extent of identified damage to the dunes is different in Bulgaria and Estonia. Given the pace and scope of such damage, there is an urgent need to work out recommendations for dune preservation and their proper management in both countries.

Materials of XXIV International Coastal Conference, devoted to the 60th anniversary of the “Sea Coasts” Working Group of RAS Council SEA COASTS – EVOLUTION, ECOLOGY, ECONOMY, 2018

The Baltic Sea region is characterized by variable winter weather conditions. Sea ice forms near ... more The Baltic Sea region is characterized by variable winter weather conditions. Sea ice forms near the Estonian coast almost every winter and is characterized by large temporal and spatial variability [1, 2].

&lt;p&gt;Leisure boating is increasing all over the world, including in the Balti... more &lt;p&gt;Leisure boating is increasing all over the world, including in the Baltic Sea region. The highest increase is expected on its eastern coast &amp;#8211; in countries of the former Soviet Union. Until the beginning of the 1990s, it was not possible to own a leisure boat in the USSR. After gaining independence, access to the sea was no longer restricted but it has taken a long time to get used to the idea that the sea is open for everyone. The economy of the Baltic countries has improved significantly over the last 30 years and the number of people affording leisure boats is rapidly growing. As a result, we need more marinas for safe and tourist-friendly boating. However, most of the old ports and their infrastructures were destroyed by the Soviet regime. Therefore, we needed to start from almost zero.&lt;/p&gt;&lt;p&gt;Developing small marinas is expensive. Many things can go wrong, especially when natural conditions are not thoroughly analyzed.&amp;#160; That is why scientific research during the planning process is an important investment.&amp;#160; An example is taken from a very small marina that had major problems with siltation. This marina is located on the northern coast of Estonia, in the region where dynamic sandy beaches quickly alternate with stable till shores.&lt;/p&gt;&lt;p&gt;The aim of the work was to find solutions to stop the siltation of the marina, to enlarge the volume of the marina without affecting the nearby sandy shores and to create the preconditions for Natura 2000 habitats while preserving the initial environment as much as possible. We developed a research methodology including: a) analysis of old maps showing historical coastal changes and processes; b) geophysical research accompanied with sediment coring and taking sediment samples for laboratory analysis; c) modeling the effects of shore processes to the marina and vice versa.&lt;/p&gt;&lt;p&gt;After several modeling exercises with different configurations of the marina, we reached satisfying solutions. Due to very fine-grained sand, it is impossible to completely avoid sediment influx into the marina. However, the final configurations need slight dredging only once in 6-8 years. We also found a solution how jetties can contribute to the healthy state of the nearby public sandy beach. The marina is located on the western side of a small peninsula with till shores. Just west from the marina is a natural sandy beach where sands are moving back and forth along the coast depending on storms. We designed the western jetties to look and function like the initial peninsula and the new marina is like an extension of the peninsula. The extracted sand from the aquatic area should be placed on the sandy beach. The added sand combined with reduced sediment movement would leave the natural beach in a more or less stable state even in the case of global sea level rise. The outer boundaries of the marina jetties look like a natural till shore. It absorbs waves&amp;#8217; energy, inhibits sand transportation to the open sea and creates preconditions similar to natural till shore habitats.&lt;/p&gt;

EGU General Assembly Conference Abstracts, Apr 1, 2019

Supplemental material, Nirgi_etal_-_HOLSEA_Radiocarbon_form for Holocene relative shore-level cha... more Supplemental material, Nirgi_etal_-_HOLSEA_Radiocarbon_form for Holocene relative shore-level changes and Stone Age palaeogeography of the Pärnu Bay area, eastern Baltic Sea by Triine Nirgi, Alar Rosentau, Hando-Laur Habicht, Tiit Hang, Tõnno Jonuks, Argo Jõeleht, Kersti Kihno, Aivar Kriiska, Mario Mustasaar, Jan Risberg, Sten Suuroja, Peeter Talviste and Hannes Tõnisson in The Holocene

Vilumaa K., Ratas U., Tõnisson H., Kont A. & Pajula R. 2017: Multidisciplinary approach to studyi... more Vilumaa K., Ratas U., Tõnisson H., Kont A. & Pajula R. 2017: Multidisciplinary approach to studying the formation and development of beach-ridge systems on non-tidal uplifting coasts in Estonia. Boreal Env. Res. 22: 67-81. The coastal ridge-swale systems in the west Estonian archipelago (Röögu, Lõimastu) and on the northern coast (Juminda), where wave and wind-built ridges are separated from each other by wet depressions, contain the records on ancient shoreline positions, major storm events and forest fires. The results are based on cartographic analysis, ground-penetrating radar survey, coring and radiocarbon dating. Seaward tilted layers in lower parts of the ridges refer to storm scarps. Water level rise and acidic waters flowing from ridges favour the accumulation of Sphagnum peat in swales. The main soil-forming processes are podzolization on ridges and paludification in swales. The obtained results show a clear dependence of soil-forming conditions and development of peat lay...

The Estonian shoreline is approximately 3800 km long and classified into five shore types (cliff,... more The Estonian shoreline is approximately 3800 km long and classified into five shore types (cliff, till, gravel, sandy, silty); approximately 95% of it is still in the natural condition. One fact which makes Estonian coastal management quite unique is that during the Soviet time most of the Estonian shoreline was a restricted zone for all civilians and all the activities in few settlements were performed under strict supervision of Soviet authorities. After independence coastal recreation and development has been part of the major national political debates. The aim of the study was to investigate the values of the coastal landscapes using two methodologies about the same shore types. The representative survey (N = 1519) among Estonian adult population was conducted with the purpose to identify: (1) public preferences for shore types; (2) annual willingness-to-pay (WTP) separately for all shore types in Estonia (a contingent valuation study). The contingent valuation survey identifie...

Baltica

Journal of Marine Science and Engineering

EGU General Assembly Conference Abstracts, Apr 1, 2019

EGU General Assembly Conference Abstracts, Apr 1, 2017

Estonian Journal of Earth Sciences, 2017

Routledge eBooks, Mar 5, 2013

Encyclopedia of the World's Coastal Landforms, …, 2010

Materials of XXIV International Coastal Conference, devoted to the 60th anniversary of the “Sea Coasts” Working Group of RAS Council SEA COASTS – EVOLUTION, ECOLOGY, ECONOMY, 2018

EGU General Assembly Conference Abstracts, Apr 1, 2019