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A new U.S. Geological Survey study provides a larger window into the future for understanding how seasonal stream temperatures may change in one of the most ecologically diverse ecosystems in North America – the Crown of the Continent Ecosystem, USA and Canada.

Profile of the North Fork of the Flathead River, Montana.
Profile of the North Fork of the Flathead River, Montana.(Credit: Jonny Armstrong. Public domain.)

Summary:  Climate warming is expected to increase stream temperatures in mountainous regions of western North America, yet the degree to which future climate change may influence seasonal patterns of stream temperature is uncertain. Much of the scientific and management focus of future changes in stream temperatures has focused instead on average summer temperatures.  This new study used a comprehensive database of stream temperature records (~4 million bi-hourly recordings) and high-resolution climate and land surface data to estimate monthly stream temperatures and potential change under future warming scenarios. Results imply increasing trends in stream temperature warming during spring, summer, and fall, with the largest increases predicted during summer. Additionally, stream temperatures characteristic of current August temperatures, the warmest month of the year, may be exceeded during July and September, suggesting an earlier onset and extended duration of warm summer stream temperatures.  The study provides the first broad scale analysis of seasonal climate effects on stream temperature in this internationally important ecosystem for better understanding climate change impacts on freshwater habitats and guiding conservation and climate adaptation strategies for aquatic species.  

The study, “Projected warming portends seasonal shifts of stream temperatures in the Crown of the Continent Ecosystem, USA and Canada”, was published in the journal Climate Change

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