Morphosedimentary evolution of Estonian coastline: role of climatic and hydrodynamic forcing over the past decades

Decadal trends in regional climate are investigated for their possible influence on the shoreline changes at a number of Baltic Sea sites in Estonia. Between 1951 and 2020, the annual mean surface air temperature at coastal stations has increased by 2.2–2.6°C, with no clear trends detected in the number of storm days during 1966–2020. However, a period of increased storminess was observed in the 1980s and 1990s. Due to post-glacial land uplift, with geocentric values between 1.3–3.5 mm yr–1, the mean relative sea level has been nearly stable or slightly falling during the study period, while the annual maxima have increased everywhere along the Estonian coast. Changes in wind regime and sea ice climate have caused temporal variations in sea level and wave conditions and, ultimately, manifested themselves in shoreline trends. Along the depositional segments, a relatively low activity of shore processes with slow erosion of the seabed and limited progradation of the beaches occurred before the 1980s. Following a clear shift in climatic conditions since the end of the 1980s and diminishing ice cover conditions along the coast, frequent storms accompanied with high sea levels resulted in increased activity of shore processes and substantial changes in alongshore morphology and beach profiles, and following an intense storm Gudrun (2005), minor events have not had substantial impact on the shore processes, with majority of the beaches attaining a new equilibrium morphodynamic state.