Abstract
AbstractThe intensity and frequency of storms are projected to increase in many regions of the world because of climate change. Storms can alter environmental conditions in many ecosystems. In lakes and reservoirs, storms can reduce epilimnetic temperatures from wind‐induced mixing with colder hypolimnetic waters, direct precipitation to the lake's surface, and watershed runoff. We analyzed 18 long‐term and high‐frequency lake datasets from 11 countries to assess the magnitude of wind‐ vs. rainstorm‐induced changes in epilimnetic temperature. We found small day‐to‐day epilimnetic temperature decreases in response to strong wind and heavy rain during stratified conditions. Day‐to‐day epilimnetic temperature decreased, on average, by 0.28°C during the strongest windstorms (storm mean daily wind speed among lakes: 6.7 ± 2.7 m s−1, 1 SD) and by 0.15°C after the heaviest rainstorms (storm mean daily rainfall: 21.3 ± 9.0 mm). The largest decreases in epilimnetic temperature were observed ≥2 d after sustained strong wind or heavy rain (top 5th percentile of wind and rain events for each lake) in shallow and medium‐depth lakes. The smallest decreases occurred in deep lakes. Epilimnetic temperature change from windstorms, but not rainstorms, was negatively correlated with maximum lake depth. However, even the largest storm‐induced mean epilimnetic temperature decreases were typically <2°C. Day‐to‐day temperature change, in the absence of storms, often exceeded storm‐induced temperature changes. Because storm‐induced temperature changes to lake surface waters were minimal, changes in other limnological variables (e.g., nutrient concentrations or light) from storms may have larger impacts on biological communities than temperature changes.
Highlights
Climate change is increasing the frequency of extreme weather events such as droughts, heat waves, and storms in many regions of the world (Coumou and Rahmstorf 2012; Seneviratne et al 2012; Nielsen and Ball 2015)
Analysis 2: Storms and temperature in stratified period We evaluated the effects of storms on epilimnetic temperature by comparing the temperature changes between the top 5th percentile of observed wind and rain events to the bottom 95th percentile observed wind and rain events, on a lake-by-lake basis
We found that the most extreme changes in epilimnetic temperature often occurred on days without storms
Summary
Climate change is increasing the frequency of extreme weather events such as droughts, heat waves, and storms in many regions of the world (Coumou and Rahmstorf 2012; Seneviratne et al 2012; Nielsen and Ball 2015). Assessment of how extreme weather events impact environmental conditions and the resulting consequences for biotic interactions and ecosystem functions and services is critically important (e.g., Cardinale et al 2012). Storms can alter thermal stratification during the thermally stratified period (Jennings et al 2012; de Eyto et al 2016; Kasprzak et al 2017) and deepen the thermocline, sometimes resulting in complete mixing of the water column (Yount 1961; Klug et al 2012; Abell and Hamilton 2015). Epilimnetic temperatures may decrease because of colder water from the hypolimnion mixing into the epilimnion (Znachor et al 2008; Umaña-Villalobos 2014), upwelling, internal waves breaking at the shore, or heat flux at the lake surface altered by wind, rain, or changes in air temperature (e.g., Andreas et al 1995; Kasprzak et al 2017; Rooney et al 2018). What constitutes a storm and how storms may affect lake processes are highly variable, making comparisons across waterbodies difficult (Stockwell et al 2020)
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