Lake Cold Spells Are Declining Worldwide

Abstract Extremes in lake surface water temperature can have profound impacts on ecosystems. Although extensive research has been conducted on lake heatwaves, little is known about cold-water extremes, referred to as lake cold spells. Here, we employ a numerical lake model to investigate global lake cold spell dynamics from 1979 to 2100. From 1979 to 2022, lake cold spells have become shorter-lasting and weaker. Change rates in the occurrence (i.e., total days) and intensity of lake cold spells are ?3.96 days decade?1 and 0.26°C decade?1, respectively. In Europe, the decline in lake cold spells is due to increases in the mean of surface water temperatures, whereas in North America, the reduction is due to decreases in the variance of surface water temperature. In the future, lake cold spells will shorten by 19.3 days and weaken by 1.97°C in the end of the 21st century under the high-greenhouse-gas-emission scenario, underscoring a shift in the surface temperature regime that may have an important influence on lake ecosystems.