Basin-wide variations in trends in water level maxima in the Baltic Sea. (15th January 2020) - Pindsoo, Katri
Abstract: Extreme water levels in the Baltic Sea have increased much faster than the global sea level rise. We employ long-term simulations with the Rossby Centre Ocean (RCO) circulation model in 1961–2005 for the quantification of (i) spatial variability of the increase rate of water level maxima in this water body and (ii) the contribution from different water level components to this increase. The increase rates of water level maxima vary from about 1.5 to 10 mm/yr. These values do not involve the vertical crust movements. The fastest increase in water level maxima occurred in the eastern Gulf of Finland (8–10 mm/yr), Gulf of Riga (6–9 mm/yr), near Klaipėda (6–8 mm/yr) and in the south-western Baltic Sea (5–7 mm/yr). Most of the increase in these locations stems from stronger local storm surges. The upsurge of the water level maxima on the shores of Sweden and in the eastern Gulf of Bothnia is typically 3–4 mm/yr and is almost fully governed by the joint impact of global sea level rise and increase in the maximum water volume of the entire sea. Highlights: Spatial variability of the increase in the Baltic Sea water level maxima quantified. Annual water level maxima increased at a rate from 1.5 to 10 mm/yr in 1961–2005. The fastest increase occurs in the eastern and south-western parts of the sea. The contribution of different drivers to water level extremes is established. The increase in water volume maxima contributes 3–4 mm/yr to water level extremes.