If donning a wetsuit and diving into an Arctic lake to get a look at underwater craters boiling up methane gas sounds like an exciting adventure, let me introduce you to Katey Walter Anthony,[1] who did just that in an Alaska lake last summer. Last week, Dr. Anthony took a break from the meeting of the American Geophysical Union here in Washington, to offer a short briefing where she explained what she found.[2]
A bit of background: Methane (“natural gas”) like carbon dioxide, is a greenhouse gas. Greenhouse gases block infra-red radiation, reducing the amount of heat escaping from earth’s surface into space: Global warming. Methane is a more potent greenhouse gas than carbon dioxide, but it breaks down much faster.
Dr. Anthony has been studying the dynamics of Arctic lakes for a couple of decades. Thermokarst lakes form when arctic soil begins to thaw, leaving voids where ice crystals have melted, causing the soil to subside. Last year, native Alaskan groups contacted Dr. Anthony seeking her help finding methane seeps which they hope to use as fuel in their remote villages.[3] As lake bottoms thaw due to a warming climate, partially-decayed plants and animals, until now locked in permafrost, are starting to thaw and resume their decay, releasing carbon dioxide and methane. Increasing release of carbon dioxide and methane from thawing permafrost is one of about half a dozen amplifying climate feedback mechanisms that scientists have documented and begun to quantify.[4]
But what Dr. Anthony found at a lake that she named Esieh, just above the Arctic Circle, is even more troubling. She spotted the telltale signs of methane release — photos show that the lake doesn’t freeze over. And when she and her team arrived to set up camp, they were greeted by a steady eruption of grapefruit-sized bubbles rising to the lake surface. Carbon dating reveals that the gas is fossil methane, not the product of decaying material in permafrost, but gas from deeper geologic formations. Dr. Anthony surmises that as permafrost melts, it unseals fissures and crevices that connect to geologic gas deposits.
It’s not clear yet whether Esieh Lake is an anomaly, or part of a larger pattern of thermokarst lakes with underground connections to geologic methane, which would have ominous implications for earth’s climate. What we do know, as Dr. Walter put it, is that “these lakes speed up permafrost thaw. It’s acceleration.” And that the amplifying effects of releasing fossil methane at an accelerating rate are not included in current climate models.[5]
Footnotes:
[1] “Katey Walter Anthony, 2009 Emerging Explorer,” National Geographic, https://www.nationalgeographic.org/find-explorers/katey-walter-anthony
[2] Thanks to Rafe Pomerance who arranged the briefing and invited me. Rafe’s long history as a champion of climate policy was reported by Nathaniel Rich in the New York Times last August: https://www.nytimes.com/interactive/2018/08/01/magazine/climate-change-losing-earth.html
[3] “Acrtic Caldroun,” Washington Post (9/22/18) by Chris Mooney with (splendid) photos by Jonathan Newton. https://www.washingtonpost.com/graphics/2018/national/arctic-lakes-are-bubbling-and-hissing-with-dangerous-greenhouse-gases/
[4] See, National Climate Assessment (2017), Chapter 15, “Surprises, Tipping Points and Compound Extremes.” https://science2017.globalchange.gov/chapter/15/, and
“The Study of Earth as an Integrated System,” NASA (2017), https://climate.nasa.gov/nasa_science/science/.
[5] KW Anthony et al, “21st-century modeled permafrost carbon emissions accelerated by abrupt thaw beneath lakes,” Nature Communications, August 15, 2018. https://www.nature.com/articles/s41467-018-05738-9
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