Stream temperatures don't parallel warming climate trend in Pacific continental United States

Network News Spring 2012, Vol. 25 No. 2
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A new analysis of streams in the western United States with long-term monitoring programs has found that despite a general increase in air temperatures over the past several decades, streams are not necessarily warming at the same rate.

Several factors may influence the discrepancy, researchers say, including snowmelt, interaction with groundwater, flow and discharge rates, solar radiation, wind and humidity. But even after factoring out those elements, the scientists were surprised by the cooler-than-expected maximum, mean and minimum temperatures of the streams.

Ivan Arismendi, a postdoc with the Andrews Forest LTER program, and coauthors analyzed long term stream temperature data from streams at the Andrews Forest as well as throughout the Pacific Northwest. Results of the research, which was supported by the U.S. Geological Survey, the U.S. Forest Service and Oregon State University, have been published online in Geophysical Research Letters (Vol. 39, L10401, 7 PP., 2012; doi:10.1029/2012GL051448): "The paradox of cooling streams in a warming world: Regional climate trends do not parallel variable local trends in stream temperature in the Pacific continental United States" (

The study also points out the value of long-term data from streams that have had minimal human impacts, such as the streams being monitored at the Andrews Forest.

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Study finds stream temperatures don’t parallel warming climate trend