LAUSR

ABSTRACT Tõnisson, H.; Suursaar, Ü.; Kont, A.; Muru, M.; Rivis, R.; Rosentau, A.; Tamura, T., and Vilumaa, K., 2018. Rhythmic patterns of coastal formations as signs of past climate fluctuations on uplifting coasts of Estonia, the 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. 611–615. Coconut Creek (Florida), ISSN 0749-0208. On uplifting and tideless Baltic Sea Coasts in Estonia, a number of elevated mid to late Holocene beach ridge systems with rhythmic patterns are identified. Such uplifted coastal formations serve as archives of past variations in sea level and climate, as well as extreme events. Luminescence dating and interpretation of airborne LiDAR elevation data were used to identify the main formation mechanisms of such beach ridge systems. More extensive (up to 100–150 ridges) and clearer ridge patterns were found on faster emerging (uplift rates around 3 mm/yr) and well-exposed western and northern coasts, where they were located on the heights of up to 18 m. The average temporal periodicity (30–40 years) in such ridge systems is in good agreement with 25–40 year cyclicity, which is detectable in Estonian tide-gauge records, wave hindcasts, regional storminess and the NAO indices. However, typical average ridge spacing was 2–3 times longer in the study areas with lower (0.5–2 mm/yr) uplift rates. It suggests that the cyclicity in ridges depends on uplift rate and is additionally enhanced or modified by decadal-scale variations in forcing conditions that is locally available.