Emerging changes in lake temperature extremes and variability in South America.

Area of Science:

• Freshwater Ecology
• Climate Science
• Limnology

Background:

• South America's freshwater systems are vital yet vulnerable to climate change.
• Understanding lake surface water temperature (LSWT) variability is crucial but limited.

Purpose of the Study:

• Analyze LSWT trends and thermal dynamics in 2,406 South American lakes.
• Investigate meteorological drivers of lake thermal behavior.
• Project future LSWT changes and heatwave dynamics.

Main Methods:

• Analysis of historical (1981-2020) and future (2021-2099) LSWT data.
• Assessment of diurnal and interannual temperature variability.
• Identification of meteorological drivers (air temperature, shortwave radiation).
• Development of a novel lake thermal typology.

Main Results:

• 97.0% of lakes show significant warming trends (+\u20090.11 K decade -1).
• 86.2% of lakes exhibit increasing diurnal temperature variability (+\u20090.02 K decade -1).
• Air temperature and shortwave radiation are key drivers, varying by region.
• Lake heatwaves are projected to intensify in frequency, duration, and intensity.

Conclusions:

• Widespread warming and altered thermal dynamics observed in South American lakes.
• Future climate change will exacerbate heatwave events.
• A new thermal typology reveals differential lake sensitivities, informing conservation efforts.