Streams are abruptly acidifying and turning orange or milky-white across vast regions of North America’s northwest. This is caused by permafrost thaw — an outcome of a warming climate that has immediate consequences for water and wildlife.

Stream acidification is driven by the weathering of naturally occurring sulphide minerals, which release acid, sulphate and toxic metals into groundwater and streams. This is known as acidic drainage. Water can become “rusty” for several kilometres downstream as iron and aluminium minerals enter streams.

Thawing permafrost means acidic groundwater can seep through the soil and react with water, oxygen and soils or bedrock containing sulphide minerals. The chemical reactions resulting from this interaction produce springs containing acid and metals.

We recently conducted a study on stream acidification with support from the Trʼondëk Hwëchʼin First Nation centred in the Tombstone Waters Observatory (TWO), a hydrological monitoring facility led by Prof. Sean Carey at McMaster University and located in central Yukon.

We found some bodies of water in the area have become highly acidic within only a few years. Such rapid shifts are rarely documented in natural watersheds and highlight how quickly permafrost thaw can alter water quality.

Rapidly changing northern environments

The emergence of acidic drainage is one example of the profound environmental changes underway across northern landscapes. Regions near the Arctic are warming more than three times faster than the global average, resulting in Arctic........

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