Climate Change and Teleconnections Amplify Lake Stratification With Differential Local Controls of Surface Water Warming and Deep Water Cooling. Issue 5 (5th March 2021)

• Record Type: Journal Article
• Authors: Oleksy, Isabella A.; Richardson, David C.
• Is Part Of: Geophysical research letters. Volume 48:Issue 5(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-03-05
• Subjects: global change -- ice phenology -- mixing action -- North Atlantic Oscillation -- stability -- stratification phenology; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL090959
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: 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. Plain Language Summary: Lakes are responding to global, regional, and local drivers of climate change, resulting in widespread lake warming and more stable layering of summer surface waters over cool deep waters. At the same time, global‐scale ocean circulation patterns are driving regional weather patterns that can enhance the effects of climate change. Using weekly observations (1985–2017) from a lake in New York State, USA, that fully mixes twice a year, we found long‐term trends of warming in surface waters and cooling in deep waters. Summer surface warming was directly controlled by rising air temperatures, but deep water cooling was associated with spring conditions, suggesting a delayed response. The overall trend of increasingly stable summer water conditions could be explained by increasing global temperatures and the spring circulation patterns in the North Atlantic Ocean, such that in years with unusually warm springs, the effects of climate change were intensified. Trends toward more extreme temperature differences between surface and deep water in relatively small lakes can be detrimental for oxygen levels and chemical cycling that ultimately support freshwater plants and animals. Key Points: Surface water warming was positively correlated with air temperature while deep water cooling was related to preceding spring conditions The stratified season length and strength has increased due to climate change and has been exacerbated by teleconnections Thermal stratification is expanding with the possibility of shifting mixing regimes from dimixis to monomixis in the future