In particular, the amount of calcium, relative to sodium and barium, is higher in the newly-thawed permafrost, and the ratio of the strontium isotope 87Sr to its counterpart 86Sr is lower. The researchers wondered if these chemical signatures of increasing thaw depth could be seen in local stream water.
Kling, who is the Robert G. Wetzel Collegiate Professor of Ecology and Evolutionary Biology, has conducted research at Toolik Lake for many years and obtained stream water samples that had been collected over an 11-year period.
When the samples were analyzed, "we saw really significant changes from year to year that were consistent with what you would predict from increasing thaw depth," Kling said.
Although the method can't reveal precisely how much permafrost thawing is occurring in particular localities, it still can be a useful adjunct to current methods, Blum said. "We'd love to be able to say that we see an increase in thickness of, say, 1 centimeter over the entire watershed, but we simply can't say where in the watershed thawing is occurring. Nevertheless, we think it's important to monitor streams in Arctic regions to keep track of these kinds of changes and follow the rate of change."
|Contact: Nancy Ross-Flanigan|
University of Michigan