Decomposition of Relative Sea Level Variations at Tide Gauges Using Results From Four Estonian Precise Levelings and Uplift Models

Abstract

Variations in Estonian sea level records (1842–2016) are interpreted using harmonic and sliding window trend analysis together with the latest findings on the crustal movements in the region of the Baltic Sea. Considering the most recent relative-to-geoid land uplift (LU) rates from the semiempirical LU model NKG2016LU_lev, it was possible, probably for the first time, to properly interpret the climate-related sea level variation components in the Estonian tide gauges. The LU relative to geoid in Estonia (0.3–3.4 mm/yr) partly compensates for the global sea level rise (GSLR). Trends in Estonian relative sea level vary site dependently between –1.05 and 1.14 mm/yr (in 1954–2016) or between –0.17 and 1.14 mm/yr (in 1900–2010), yielding a “local sea level rise” (approximately 2.2 to 2.8 mm/yr in 1900–2010), which is faster by ∼0.8 mm/yr than the GSLR over similar period. This gap mainly originates from local land subsidence and variations in water exchange processes between the Baltic Sea and the World Ocean. Moreover, due to high intra- and inter-annual variability (standard deviations in detrended monthly data series from 20 to 22 cm), the sea level trend estimates are not stable enough and the usability of Estonian time series is relatively low for contributing to GSLR estimations.