Escalating Extremes over Descending Trends of the Northern Baltic Proper Wave Fields

Interannual variations of average wave conditions and extreme wave storms in the northern Baltic Sea are studied based on long-term time series from Almagrundet (1978–2003) and Vilsandi (1954–2005), wave statistics from the middle of the northern Baltic Proper, and simulations of wave properties in cyclone Gudrun in January 2005. The annual mean wave height varied insignificantly in the 1960s–1970s, increased considerably in the 1980s, was highest in the mid-1990s, and rapidly decreased between 1998–2005. The frequency of extreme wave conditions (H_s ⩾ 7 m) has not changed significantly since the end of the 1970s. The overall recorded maximum H_s between 1978–2005 is 7.8 m. The estimated maximum H_s in cyclone Gudrun was 9.5 m.