Release of carbon from Arctic soils

Arctic soils are set to release a lot of carbon — probably more than plants can absorb Author: Yereth Rosen, ADN.com 3 Dec 16 As temperatures have risen in the Arctic and worldwide, so have worries about how much carbon might stream into the atmosphere from warmer soils.

Will enough new carbon be released from the ground, potentially exacerbating the global warming cycle? And will new-growth carbon dioxide-absorbing plants growing in warmer conditions be able to keep pace?

Now scientists have some better answers to both questions — and they’re troubling.

Globally, warming will drive 55 petagrams (that’s 55 billion metric tons or 55 trillion kilograms) of carbon gases from soils into the atmosphere by mid-century, according to a comprehensive study led by researchers at Yale. That amount is equal to about 17 percent of projected emissions from global fossil-fuel burning and other human activities.

The study, published Wednesday in the journal Nature, cites the highest latitudes and highest altitudes as the biggest contributors of carbon from the ground.

While warmer soils all around the world stimulate more of the below-ground microbial activity that produces carbon gases, the changes are most striking in permafrost regions — the Arctic, where warming is happening at least twice as fast as the global rate, and the tops of the highest mountains. In those high latitudes and high altitudes, permafrost thaw is freeing once-locked carbon left by long-ago decayed plants and animals, and making it available to the microbial processes that produces gases that are emitted above the ground.

“Thaw depths are getting deeper,” said study co-author Jeff Welker, a biology professor and Fulbright Distinguished Arctic Chair at the University of Alaska Anchorage.

The global calculation for the mid-century total for carbon emitted from soil — an amount roughly equivalent to all U.S. carbon emissions from human activities — is a gross figure, not the net after uptake by plants above the ground’s surface, Welker said.

But prospects for Arctic plants to absorb the extra carbon gases appear dim, according to another newly published study led by scientists at the University of Alaska Fairbanks.

On at least part of Alaska’s North Slope, new carbon streaming out of the soil is already outpacing any carbon uptake by plants on top of the ground and the area has become a net carbon emitter, according to the study, published in the journal Ecosystems.

The UAF-led study monitored eight years of year-round carbon fluxes between the air and the soil, making it a very rare long-term project. (Most studies tracking carbon gas movements only monitor in the summer.) The study used tripod-mounted sensors to measure carbon dioxide, the dominant greenhouse gas, and methane being released and absorbed by different types of tundra at a test site in the Brooks Range foothills……

The result is an ominous sign for the future, signaling more climate-warming gas pouring into a region that has already warmed dramatically, said co-author Syndonia Bret-Harte, also of UAF’s Institute of Arctic Biology.

“It could be a profound feedback to global climate from a relatively moderate area of the earth,” Bret-Harte said……https://www.adn.com/arctic/2016/12/01/led-by-arctic-warmed-soil-poised-to-pour-vast-amounts-of-carbon-into-atmosphere/