Arctic Pastures Emit More CO2 In Winter Than They Absorb In The Summer

The reason Caribou and Reindeer paw through the snow to graze in the winter is because the pasture is thriving throughout the long winter night

It’s not so cold beneath that snow

These days warmer Arctic pastures emit 1.7 billion tonnes of CO2, twice the amount each year as previously thought

New research just published in the Journal Nature has revealed that Arctic winter and severity of its freezing effects on Arctic pastures and permafrost has eased dramatically. Today Arctic pasture soils continue to thrive in the winter months rather than being in a deep freeze stasis and are respiring far more CO2 in winter than tundra plants can absorb during the summer. The finding means the extensive belt of tundra around the globe — a vast reserve of carbon that dwarfs what’s held in the atmosphere — is becoming a very problematic source of greenhouse gas emissions exacerbating global climate change.

Jocelyn Egan of Dalhousie Earth Science PhD Candidate

“In a given year, more carbon is being lost than what is being taken in. It is happening already.” Jocelyn Egan a PhD candidate at Dalhousie University in Canada said.

Not as cold as it used to be.

The research by scientists in 12 countries and from dozens of institutions is the latest warning that northern natural systems that once reliably kept carbon out of the atmosphere are starting to release it. Until now, little had been reported about winter emissions from permafrost and the soil above it. Most scientists assumed that plant respiration and microbial processes that release the gases came to a halt in the cold.

“People think in the winter, there’s no respiration, that the microbes eating the carbon that produce these emissions aren’t active, which isn’t actually the case.”

Arctic Pasture Science

To study the true nature of the Arctic pastures scientists placed carbon dioxide monitors along the ground at more than 100 sites around the circumpolar Arctic to see what was actually happening and took 1,000’s of measurements. The data shows that much more CO2 was being released than previously thought. Emissions of carbon dioxide emissions that were measured when modeled for the whole of the Arctic are now estimated at 1.7 million tonnes a year, about twice as high as previous estimates.

Lichens, stunted shrubs like blueberry, and moss dominate Arctic Pastures. Click to enlarge

Arctic pasture tundra plants are thought to take in just over one billion tonnes of CO2 from the atmosphere every year during the growing season. The net result is that Arctic soil around the globe is sure to be releasing more than an additional 600 million tonnes of CO2 annually than previously reported. This is less but just barely than the combined total CO2 emissions of the two big Arctic nations, Russia and Canada.

The here-to-fore catch-all generalization about Arctic pastures, so typical of science commentary where facts are missing, has been that carbon absorbed by tundra plants to sustain their photosynthesis during the summer more or less made up for what was emitted in the winter.

Now that we have real data we see that’s not what’s happening, said Egan

“We’re seeing that the value emitted in the winter is larger than the net uptake for the growing season.”

The pace of these Arctic emissions is likely to increase.

Arctic pasture CO2 emission models predict emissions might approach 3.5 billion tonnes by the end of the century – Click to enlarge

Under a business-as-usual scenario, emissions from northern soil will be likely to release 41 percent more carbon by the end of the century. But the Arctic is already seen to be warming at three times the pace of the rest of the globe. Even if significant, yet to be invented, mitigation efforts were to be deployed, emissions will still increase by 17 percent, said the report.

Importantly Egan notes the research wasn’t able to deploy the instruments needed to measure methane, a greenhouse gas about 80-100 times more potent than carbon dioxide as a greenhouse gas that is also released during the winter from Arctic pastures. Much allied research suggests the potency of methane release from Arctic pasture soils is likely far greater than the more benign CO2 release. Recent data-derived estimates of high-latitude terrestrial winter methane/CH4 emissions range up to 9 TgC yr−1 for Arctic tundra. That is about 1/100th of the CO2 emission, but given each methane unit is equal to about 100 CO2 units the two are roughly equal in the impact on climate change and the severity of this news becomes dire. With this new research showing winter CO2 emissions have been so drastically underestimated one can be relatively certain that the same underestimation flaws have been prevalent in annual CH4 emissions released from Arctic pastures during the winter.

Her findings echo previous studies. Last summer, research suggested that larger, hotter wildfires are turning boreal forests into carbon sources. Another paper found that instead of melting slowly and steadily, permafrost is subject to sudden collapses that speed up the rate of carbon release.

Some people are advocating ideas aimed at ‘refreezing the Arctic’ but when one views the area involved as seen in the graphics above such technological hardware would easily have to exceed the entire installed technology base of a large part of the industrialized world. For anyone who has not spent time in the vastness of the Arctic, its scale is simply unimaginable.

The Arctic is among the first global ecosystems to suffer most from yesterday’s trillion tonne dose of fossil fool age CO2. With yesterday’s CO2 driven global warming now ‘baked in’ the Arctic is going to undergo a radical change this century. Regardless of whether the world curtails some part of tomorrow’s CO2 emissions, it is yesterday’s CO2 that has already defined the future of the Arctic.