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A phenomenological approach shows a high coherence of warming patterns in dimictic aquatic systems across latitude
- Wagner, Annekatrin, Hülsmann, Stephan, Paul, Lothar, Paul, Rüdiger J., Petzoldt, Thomas, Sachse, René, Schiller, Thomas, Zeis, Bettina, Benndorf, Jürgen, Berendonk, Thomas U.
- Marine biology 2012 v.159 no.11 pp. 2543-2559
- cold, irradiation, lakes, latitude, prediction, spring, summer, surface water, temperature profiles, Baltic Sea, North Sea
- To predict the coherence in local responses to large-scale climatic forcing among aquatic systems, we developed a generalized approach to compare long-term data of dimictic water bodies based on phenomenologically defined hydrographic events. These climate-sensitive phases (inverse stratification, spring overturn, early thermal stratification, summer stagnation) were classified in a dual code (cold/warm) based on threshold temperatures. Accounting for a latitudinal gradient in seasonal timing of phases derived from gradients in cumulative irradiation (2.2 days per degree latitude), we found a high spatial and temporal coherence in warm–cold patterns for six lakes (84 %) and the Baltic Sea (78 %), even when using the same thresholds for all sites. Similarity to CW-codes for the North Sea still was up to 72 %. The approach allows prediction of phase-specific warming trends and resulting instantaneous or time-delayed ecological responses. Exemplarily, we show that warming during early thermal stratification controls food-web-mediated effects on key species during summer.