A 2023 heat wave has turned tropical lakes in the Amazon into shallow, very hot pools. An effect of climate change.
Heat waves transform the lakes of the Amazon region into shallow, murky and bubbling basins. A climatic event of this type, in 2023, caused the temperatures of these bodies of water to rise to 41°C, brought their depths to their minimums and led to the collapse of their fauna, as well as isolating the human communities that move and fish in their waters.
The discovery, published on Scienceis worrying because heat waves are increasingly frequent in the Amazon region, and because, until now, the impacts of climate change on tropical lakes had been underestimated.
Like tubs in a spa
Aquatic ecosystems are warming regularly and lakes, very sensitive to variations in temperature increases, are considered sentinels of climate change. A collaboration of scientists led by the Mamirauá Institute for Sustainable Development in the Amazon presented an analysis of the water temperature of 10 lakes in the central Amazon during a heat wave that hit the region in 2023, based on satellite measurements and studies of alterations in their water levels.
Temperatures in 5 of the 10 lakes analyzed reached exceptionally high daytime values, above 37 °C. In one case – that of Lake Tefé, which reaches just a couple of meters at its lowest point – the waters reached 41°C, a temperature higher than that of a hot tub in a spa.
Still and boiling waters
The low depth of the water, the solar radiation in cloudless skies, the high turbidity but – above all – unusually calm winds, which slowed down the dispersion of heat through evaporation and during the night hours, contributed to the situation. This factor of air immobility was even more effective than the increase in temperatures.
The new normal?
2023 is not an isolated case. Similar temperature conditions occurred in September and October 2024, and the new study concludes that over the past 30 years or so, Amazon lakes have warmed by 0.3-0.8°C per decade, faster than the global average.
During the 2024 drought, Lake Tefé shrank by 75% in size, and another lake, Badajós, by 90%. The described droughts have caused mass deaths among the fish in the lakes and among the freshwater dolphins that populate their waters. Fish fauna is fundamental to the economy of these areas: the livelihood of local populations is based significantly on fishing.
