Twentieth Century Reanalysis version 3 as a source of information on long-term trends (1806–2022) in lake surface water temperature changes in Central Europe (Poland)

Water temperature is one of the fundamental characteristics of the hydrosphere, determining the functioning of its various components. In the case of lakes, surface water temperature shows a strong correlation with air temperature, and this relationship forms the basis for reconstructing the thermal regime of lakes. The study uses the Twentieth Century Reanalysis (20CRv3) meteorological dataset to reconstruct the surface water temperature of seven lakes in Poland for the period 1806–2022. This approach significantly expands the current state of knowledge, particularly for Central Europe, and includes periods predating significant human impact on the environment. Over the course of more than 200 years, an increase in water temperature has been observed, averaging 0.081 °C per decade across all studied lakes. Considering the changes in water temperature in the studied lakes, several distinct phases can be observed, which generally reflect changes in climatic conditions. Based on the results of the Pettitt test, the characteristic points include the 1840s, the 1940s, and the late 1980s. Rapid warming has been recorded in recent decades, and current studies suggest this trend is likely to continue in the future. This situation calls for multidisciplinary consultation and subsequent action to develop strategies for mitigating the impact of global warming on lake ecosystems.