Climate Change and Teleconnections Amplify Lake Stratification With Differential Local Controls of Surface Water Warming and Deep Water Cooling

Temperate lakes are experiencing increases in warming and stratification duration while global-scale teleconnections potentially exacerbate effects of climate change. We examined interannual surface and deep water temperature change and stratification phenology in a long-term, weekly data set (1985-2017) from a dimictic lake in New York State, USA. We developed a metric, called mixing action, to capture multiple facets about the stratified period. We found warming in surface waters and cooling in deep water. Surface warming was positively correlated with air temperature. Deep water cooling was positively correlated with spring mixing period length and deep water spring temperature, indicating a lag effect. Mixing action was correlated with global temperature anomaly and spring North Atlantic Oscillation index. With increasing summer stratification strength and length, dimictic lakes like Mohonk may continue shifting toward monomictic mixing regimes with increasing summer hypolimnetic anoxia and changing lake biogeochemistry, productivity, and habitat for aquatic organisms.