July 24, 2013 12:20 pm
The temperature in the Arctic is rising, the snow is melting, and the landscape is getting greener—that is, when it’s not on fire. In the 10,000 years since the end of the last ice age, says a new study lead by Ryan Kelly, the severity of Arctic fires—the damage they do to the areas, particularly the soil, that they burn—is the highest it’s ever been. The closest match, the researchers say, was a 500-year stretch known as the Medieval Climate Anomaly, a period that ended around 750 years ago and was defined by warm, dry conditions in the Northern Hemisphere.
The modern boreal forest of Alaska, where the scientists did their study, took shape around 3,000 years ago. Along with the sharp increase in fire severity, the frequency of Arctic wild fires has been increasingly recently, too. Kelly and the others write that the frequency of fires is the highest it has been in this 3,000 year stretch.
Predictions of future Arctic wildfires, say the scientists, “almost ubiquitously suggest increased frequency, size, and/or severity of burns in coming decades as a result of future warming.” But Kelly and colleagues point out that making these sorts of predictions might not be quite so simple. They say that some trees are more flammable than others, and just like during the Medieval Climate Anomaly, an increase in strong fires may be increasing the prevalence of less flammable species. During the Medieval Climate Anomaly, this type of shift capped the extent of the fires, and, the scientists write, a similar change that seems to be going on now “may stabilize the ﬁre regime, despite additional warming.”
So, Arctic greening and changes in the types of plants might put a damper on the recent increases in Arctic fire frequency. Or, it might not. “The present ﬁre regime seems to have surpassed the vegetation-induced limit that constrained burning during the [Medieval Climate Anomaly],” Kelly and his colleagues say. Modern climate change seems to be more dramatic than even that five-hundred-year warm period centuries ago, so we’re really not entirely sure what’s going to happen to the Arctic. Maybe something will dampen the blaze, like it has in the past, or maybe it won’t. We might, as the scientists say, be headed for a “novel regime of unprecedented fire activity” in the Alaskan Arctic.
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