[MCN] PNAS September 22, 2025 -- Riverine heat waves on the rise, outpacing air heat waves

[Lance Olsen]

PNAS September 22, 2025

Riverine heat waves on the rise, outpacing air heat waves
Kayalvizhi Sadayappan <https://www.pnas.org/doi/10.1073/pnas.2503160122#con1>  and Li Li <https://www.pnas.org/doi/10.1073/pnas.2503160122#con2> 

https://doi.org/10.1073/pnas.2503160122

Significance

Riverine heat wave events—periods of abnormally high riverine water temperatures (WT)—can substantially impair aquatic ecosystems, water quality, and food and energy production. However, comprehensive analysis of riverine heat waves is still emerging, long hindered by fragmented and discontinuous WT data. Here, we used a deep learning model and reconstructed consistent daily WT in 1471 U.S. river sites (1980–2022). Results show that riverine heat wave events occur less frequently and intensively but last nearly twice as long as air heat waves. Alarmingly, riverine heat waves have risen at much faster rates than air heat waves. Results here underscore the need for coordinated monitoring and data consolidation efforts for riverine heat waves, and their incorporation into global climate risk assessment and adaptation policies.

Abstract

While air heat waves often grab headlines, riverine heat waves have gone quietly unnoticed because rivers are commonly perceived as cool refuges. Analysis of riverine heat waves has been hindered by fragmented datasets, despite a proliferation in water-temperature monitoring with sensors and satellites. Here, we analyze riverine heat wave events by training one single deep learning (long short-term memory) model and reconstructing consistent and continuous daily water temperatures (WT) in 1471 sites in the Contiguous United States (1980–2022). We show that riverine heat waves occur at about half the frequency (2.3 versus 4.6 events/year), a third intensity (2.6 versus 7.7 °C/event), but almost double the duration (7.2 versus 4.0 d/event) of air heat waves. Riverine heat wave events have increased at double to quadruple rates of air heat wave events, amounting to an additional 1.8 events/year in frequency, 0.43 °C/event in intensity, 3.4 d/event in duration, and 7 to 15 additional thermal stress days for aquatic ecosystems in 2022 compared to 1980. Rising riverine heat waves have outpaced those of air heat waves in 65 to 76% of the sites, particularly in regions experiencing accelerated warming (e.g., the Rockies). Riverine heat wave trends are driven predominantly by climate-induced changes such as warming and dwindling snowpacks and water flow. Human activities do play important roles: large dams elongate, whereas agriculture reduces heat waves. These results highlight anthropogenic climate change as the primary external driver, whereas human-induced structural changes as the secondary internal modulators of river response to heat disturbance. The widespread rise of riverine heat waves threatens aquatic ecosystems and water-energy-food security, underscoring the need for their global characterization and risk assessment.




=————————————————————------===-------------------------------------------------=

“Full of recent references and statistics, Harvesting the Biosphere adds to the growing chorus of warnings about the current trajectory of human activity on a finite planet, of which climate change is only one dimension. 

“One can quibble with some assumptions or tweak Smil’s calculations, but the bottom line will not change, only the time it may take humanity to reach a crisis point.”

Stephen Running. “Approaching the Limits” Science 15 March 2013.

Book review. Harvesting the Biosphere: What we have taken from Nature. by Vaclav Smil .  MIT Press, Cambridge, MA, 2012. 315 pp. $29, £19.95. ISBN 9780262018562.

=————————————-----------------------===—----------------------------—————————=

“Man …  is alone, abandoned on earth in the midst of his infinite responsibilities, without help, with no other aim than the one he sets himself, with no other destiny than the one he forges for himself on this earth.”

Jean-Paul Sartre (1905-1980)


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://bigskynet.org/pipermail/missoula-community-news_bigskynet.org/attachments/20250924/9479e02c/attachment.htm>