How Alaska’s Recent Heat Wave May Worsen Climate Warming

, Kendall Science Fellow | July 11, 2019, 12:17 pm EDT
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Over the holiday weekend, three cities in Alaska experienced record heat with temperatures in Anchorage reaching 90°F. In a city where local July temperatures averaged 61°F in 2018, this extreme heat illustrates the dramatic effects of climate change in northern regions of the world. These record-breaking temperatures, however, could further intensify climate warming by priming Alaskan landscapes to release carbon and heat-trapping gases in two major ways.

First, extreme heat in Alaska may worsen climate change by accelerating the thaw of carbon-rich permafrost. Permafrost, which underlies most of Alaska, locks away vast quantities of carbon in continuously frozen earth.  As temperatures rise and permafrost thaws, this carbon becomes vulnerable to decomposition, which can release carbon dioxide and methane into the atmosphere. As a result, extreme heat, like that seen over the weekend, may initiate a positive feedback loop (warming begets carbon release begets warming, etc.) that threatens to further exacerbate climate warming.

Permafrost distribution in Alaska (purple shows continuous permafrost, pink shows discontinuous permafrost, and green shows sporadic permafrost). Data from National Snow & Ice Data Center.

Second, extreme heat can also prime Alaska’s landscapes for wildfires, which release huge amounts of heat trapping gases as they burn. Alaska’s soils are chock full of carbon, both in permafrost and the overlain active layer that thaws out each summer. By drying out these soils and above-ground vegetation, high temperatures create conditions that favor not only ignition, but also fire spread.

Recent wildfires have already surpassed historic return intervals and intensities, burning both a larger forested area and deeper into carbon-rich soils, magnifying the emissions from Alaskan wildfires. In a truly unfortunate synergism, wildfires can also accelerate permafrost thaw by removing the insulating active layer.

To avoid the most catastrophic consequences of climate change, we must reduce emissions and protect what carbon is already stored, including carbon stored below ground in Alaska. While protecting permafrost carbon will require global reductions in emissions and stabilization of global temperatures, Alaskan wildfires present an unusual opportunity – one where we can intervene and reduce emissions, using a technique (fire management) with which we are already well acquainted.  Despite this opportunity, fire management is largely overlooked as an approach to reduce emissions.

As global temperatures climb, extreme heat, like we saw over the holiday, not only harms the communities that live there but also threatens to increase emissions out of Alaska and further destabilize our climate.  We ignore these feedbacks at our peril, because what happens in Alaska will have consequences for us all.

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  • Killian O’Brien

    Another point, which I cannot quantify and may or may not be accurate, but I believe is, is the triggering of tipping points of permafrost emissions. A heatwave like this may “condition” Alaskan permafrost by driving melt deeper than is within normal bounds, thus getting a wet layer below which refreeze does not occur, thus accelerating melt by… never freezing again.

    That last point is in the literature. There are already areas that a melting deep enough that the frozen layer caps them, but does not stop their melt processes, and, of course, when summer rolls around there is that much less to melt and that much more melt occurs.

    Can a heatwave and fires have such an affect to drive melt deeper?

    How can it not?