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Twenty years of spatially coherent deepwater warming in lakes across Europe related to the North Atlantic Oscillation
Author(s) -
Dokulil Martin T.,
Jagsch Albert,
George Glen D.,
Anneville Orlane,
Jankowski Thomas,
Wahl Bernd,
Lenhart Brigitte,
Blenckner Thorsten,
Teubner Katrin
Publication year - 2006
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2006.51.6.2787
Subject(s) - hypolimnion , north atlantic oscillation , environmental science , trophic level , thermal stratification , climate change , oceanography , climatology , atlantic multidecadal oscillation , physical geography , geology , nutrient , geography , eutrophication , ecology , thermocline , paleontology , biology
Twenty to fifty years of annual mean deepwater (hypolimnetic) temperature data from twelve deep lakes spaced across Europe (2°95'W to 14°0'E, 46°27' to 59°00'N) show a high degree of coherence among lakes, particularly within geographic regions. Hypolimnetic temperatures vary between years but increased consistently in all lakes by about 0.1–0.2°C per decade. The observed increase was related to the weather generated by largescale climatic processes over the Atlantic. To be effective, the climatic signal from the North Atlantic Oscillation (NAO) must affect deep lakes in spring before the onset of thermal stratification. The most consistent predictor of hypolimnetic temperature is the mean NAO index for January–May (NAO J–M ), which explains 22–63% of the interannual variation in deepwater temperature in 10 of the 12 lakes. The two exceptions are remote, less wind‐exposed alpine valley lakes. In four of the deepest lakes, the climate signal fades with depth. The projected hypolimnetic temperature increase of approximately 1°C in 100 yr, obtained using a conservative approach, seems small. Effects on mixing conditions, thermal stability, or the replenishment of oxygen to deep waters result in accumulation of nutrients, which in turn will affect the trophic status and the food web.