Monday, May 14, 2012

Warming experiment update

The heat exchanger continues to do a great job. Below is a plot of the latest data, showing mean daily temperatures in the upstream reference reach and experimentally warmed reach. The arrow indicates the start of the manipulation on 22 October 2011. A couple of things to note. One can see the effect of the heat exchanger freezing up for ten days in December 2011 when temperatures returned to baseline levels. Second, temperatures were very variable in both reaches during the first winter, presumably because of rainfall and snowmelt. During this last winter, a thick snowpack buffered temperatures upstream of the warm water diffuser, resulting in much less variability. Our mean warming is 2.25 C as of the end of April 2012. That should be creeping up slowly now that snowmelt is over and discharge in the stream decreases.

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