Physical Oceanography Physical Oceanography 1573-160X 20250204 Analysis of observations and methods of calculating Hydrophysical fields in the ocean Research Article Long-Term Dynamics of the Annual Average Wave Heights in the Baltic Sea https://orcid.org/0000-0002-7593-9739 B-4523-2017 56998131000 2884-6132 Sokolov A. N.
Russian Federation
tengritag@gmail.com https://orcid.org/0000-0001-7988-1717 I-6118-2016 6507102508 2691-5872 Chubarenko B. V.
Russian Federation
chuboris@mail.ru Shirshov Institute of Oceanology, Russian Academy of Sciences Moscow Russian Federation Immanuel Kant Baltic Federal University Kaliningrad Russian Federation 30 04 2025 32 2 197 210 01 10 2024 16 10 2024 29 01 2025 Copyright ©; 2025, A. N. Sokolov, B. V. Chubarenko 2025 A. N. Sokolov, B. V. Chubarenko https://creativecommons.org/licenses/by-nc/4.0/ https://physical-oceanography.ru/repository/issues/2025/02/04/

Purpose. The paper is purposed at revealing the time periods since the mid-20th century when the annual average wave heights in the Baltic Sea tended to increase or decrease, assessing the statistical significance of potential time trends, as well as analyzing the statistical relationship between annual average wave heights in the Baltic Sea and the North Atlantic Oscillation.

Methods and Results. The analysis is based on several points located in different parts of the Baltic Sea, in which the data on annual average wave heights cover the time intervals of several decades and are obtained by instrumental methods (one point), from field observations (two points) and modeling results (six points). The time series of annual average wave heights at these points are divided into the time segments of conditional monotony with predominant tendencies towards increase or decrease. The rates of change in wave heights at each segment and statistical significance of potential time trends are assessed using the non-parametric techniques. In the majority of cases, the trends within the segments under consideration are found to be statistically significant at the 90% level or more and the rates of change in the trend can range from 5 to 20 mm per year. The statistical relationship between annual average wave heights and the North Atlantic Oscillation is evaluated using the Pearson and Spearman correlation analysis. The correlation coefficients between the North Atlantic Oscillation indices and the annual average wave heights are statistically significant at the 90% level or more. Their numerical values within the interannual variability range constitute 0.3–0.6 and those between the five-year moving averages – 0.4–0.8.

Conclusions. The increasing and decreasing phases in wave heights in the Baltic Sea alternate, at that each phase lasts ∼ 20 years. The time trends for each phase are statistically significant at least at some points in the sea. The correlation between the North Atlantic Oscillation index and the annual average wave heights is statistically significant but not high. Such correlation can account for ∼ 30–65% of the variations in wave characteristics.

 Baltic Sea significant wave height NAO index time trend statistical significance correlation coefficient The work was carried out within the framework of state assignment of IO RAS (theme FMWE-2024-0025).

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