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dohboi wrote:Bill McKibben (@billmckibben)

7/16/18, 2:00 PM

“...We've swamped the atmosphere with so much methane that it is producing new cloud patterns. That seems a tad ominous ...”

https://twitter.com/billmckibben/status ... 5554228227

Methane Is Giving Noctilucent Clouds a Boost

https://www.wunderground.com/cat6/Metha ... ouds-Boost

onlooker wrote:

38177018_10216822695138922_8519915337901146112_n.jpg

Methane belching in progress near Barrow Alaska

The researchers found the release of greenhouse gases beneath thermokarst lakes is relatively rapid, with deep thawing taking place over the course of decades. Permafrost in terrestrial environments generally experiences shallow seasonal thawing over longer time spans. The release of that surface permafrost soil carbon is often offset by an increased growth in vegetation.

“Thermokarst lakes provide a completely different scenario. When the lakes form, they flash-thaw these permafrost areas,” said Walter Anthony, an associate professor with UAF’s Water and Environmental Research Center. “Instead of centimeters of thaw, which is common for terrestrial environments, we’ve seen 15 meters of thaw beneath newly formed lakes in Goldstream Valley within the past 60 years.”

Emissions from thermokarst lakes aren’t currently factored into global climate models because their small size makes individual lakes difficult to include. However, the study’s authors show that these lakes are hotspots of permafrost carbon release. They argue that not including them in global climate models overlooks their feedback effect, which occurs when the release of greenhouse gases from permafrost increases warming. That feedback is significant because methane is about 30 times more potent than carbon dioxide as a heat-trapping gas.

Existing models currently attribute about 20 percent of the permafrost carbon feedback this century to methane, with the rest due to carbon dioxide from terrestrial soils. By including thermokarst lakes, methane becomes the dominant driver, responsible for 70 to 80 percent of permafrost carbon-caused warming this century.

Adding thermokarst methane to the models makes the feedback’s effect similar to that of land-use change, which is the second-largest source of human-made warming.

Unlike shallow, gradual thawing of terrestrial permafrost, the abrupt thaw beneath thermokarst lakes is irreversible this century.

Even climate models that project only moderate warming this century will have to factor in their emissions, according to the study.

“You can’t stop the release of carbon from these lakes once they form,” Walter Anthony said.

“We cannot get around this source of warming.”

Permafrost carbon feedback (PCF) modeling has focused on gradual thaw of near-surface permafrost leading to enhanced carbon dioxide and methane emissions that accelerate global climate warming.

These state-of-the-art land models have yet to incorporate deeper, abrupt thaw in the PCF.

Here we use model data, supported by field observations, radiocarbon dating, and remote sensing, to show that methane and carbon dioxide emissions from abrupt thaw beneath thermokarst lakes will more than double radiative forcing from circumpolar permafrost-soil carbon fluxes this century. Abrupt thaw lake emissions are similar under moderate and high representative concentration pathways (RCP4.5 and RCP8.5), but their relative contribution to the PCF is much larger under the moderate warming scenario.

Abrupt thaw accelerates mobilization of deeply frozen, ancient carbon, increasing 14C-depleted permafrost soil carbon emissions by ~125–190% compared to gradual thaw alone.

These findings demonstrate the need to incorporate abrupt thaw processes in earth system models for more comprehensive projection of the PCF this century.

Katey Walter Anthony has studied some 300 lakes across the tundras of the Arctic. But sitting on the mucky shore of her latest discovery, the Arctic expert said she’d never seen a lake like this one.

The first time Walter Anthony saw Esieh Lake, she was afraid it might explode - and she is no stranger to the danger, or the theatrics, of methane.

At first, the sheer volume of gases at Esieh Lake was slightly terrifying...

In a 2,000-square-kilometre area around the Barrow Peninsula in northern Alaska, for instance, the team calculated that lakes release an average of 0.6 grams of methane per square metre of water surface each year — which equates to around 141 kilograms of methane per square kilometre. That is about 84% lower than some previous estimates based on measurements at individual lakes, Engram says, but lines up well with estimates based on atmospheric measurements.