A stream.
The image shows evidence of acid inputs resulting from the weathering of sulfide minerals, which leach into a stream from a hillslope. The red color is due to the precipitation of iron and aluminum oxides in the stream as added acidity is buffered. Although these processes remove some metals, rivers downstream of such point sources have higher levels of sulfate and metals, including manganese, zinc, nickel, cadmium and rare earths. Credit: Evinger et al. [2026], Figure S1e
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: AGU Advances

In the September 2026 issue of AGU Advances, Evinger et al. [2026] describe abrupt changes in the chemistry of streams and rivers that drain the Brooks Range in Alaska. Long-term observations of rivers reveal an increase in sulphate and zinc concentrations following an unusually warm winter in 2019. The authors investigate potential sources and find that the changes could be attributed to accelerated oxidative weathering of sulfide minerals exposed by thawing permafrost.

The accompanying Viewpoint, Skierszkan [2026], discusses how similar shifts in stream chemistry have been observed in the Yukon region, and the potential regional scope associated with permafrost areas underlain by sedimentary rocks containing sulfide minerals. Together, these contributions highlight the unexpected impact of melting Arctic permafrost and elaborate on how this new environmental concern can affect regional water quality, ecosystems, and human populations.

Citations:

Evinger, T. G., O’Donnell, J. A., Carey, M. P., Koch, J. C., Baughman, C. A., Hill, K. R., et al. (2026). Abrupt onset and persistent downstream effects of acid rock drainage on rivers across northwest Arctic Alaska. AGU Advances, 7, e2026AV002407. https://doi.org/10.1029/2026AV002407

Skierszkan, E. K. (2026). Permafrost-thaw driven acid-rock drainage threatens Arctic aquatic ecosystems. AGU Advances, 7, e2026AV002822. https://doi.org/10.1029/2026AV002822

—Susan Trumbore, Editor, AGU Advances

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Text © 2026. The authors. CC BY-NC-ND 3.0
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