Wind induced impacts on hypolimnetic temperature and thermal structure of Candlewood Lake (Connecticut, U.S.A.) from 1985–2015

Abstract

Climate change has affected freshwater lakes in many ways, including shifts in thermal structure, stability, ice cover, annual mixing regimes and length of the growing season, all of which impact ecosystem structure and function. We examine the impacts climate variables, especially wind speed, had on water temperature and thermal stratification at three sites in Candlewood Lake (Connecticut, U.S.A.) between 1985 and 2015. Despite the lack of regional time-related trends in air temperature or precipitation over the 31 year period, there was a significant decline in wind speed during spring and summer months, with a mean decline of 31% over the study period. Even though a wide range in mean July epilimnetic temperature (22.8–28.2°C) was observed, there was no trend over time. In contrast, a significant cooling trend was recorded for the hypolimnion that was highly correlated with the declining wind speed. Decreasing wind speed was also correlated with an increase in the strength of the thermocline estimated from maximum RTRM values. Despite the lack of a warming trend in surface waters over the entire study period, the strength of summer thermal stability estimated using total RTRM scores was highly correlated with epilimnetic temperature. The potential consequences of declining wind speed, a cooling hypolimnion, and a stronger thermocline are discussed.