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Media contact: Diana Kenney dkenney@mbl.edu; 508-685-3525

The cold, treeless tundra landscape that encircles the Earth just below the Arctic ice caps - including much of Alaska and Canada - is known to contain huge stores of carbon in its frozen soils. But a big unknown in global change biology has been whether a warming climate will cause this carbon to be released as carbon dioxide, a greenhouse gas, creating a positive feedback loop into climate change.

Today, a massive synthesis study confirms that climate warming shifts the dynamics of tundra environments and makes them release stores of trapped carbon. These changes could transform tundras from carbon sinks into a carbon source, exacerbating the effects of climate change.

A team of over 70 scientists, including the late Jianwu (Jim) Tang, senior scientist in the MBL Ecosystems Center, used open-top chambers (OTCs) to experimentally simulate the effects of warming on 28 tundra sites around the world. OTCs basically serve as mini-greenhouses, blocking wind and trapping heat to create local warming. 

The warming experiments led to a 1.4°C increase in air temperature and a 0.4°C increase in soil temperature, along with a 1.6% drop in soil moisture. These changes boosted ecosystem respiration (carbon dioxide production) by 30% during the growing season, causing more carbon to be released because of increased metabolic activity in soil and plants. The changes persisted for at least 25 years after the start of the experimental warming – which earlier studies hadn’t revealed.

‘We knew from earlier studies that we were likely to find an increase in respiration with warming, but we found a remarkable increase – nearly four times greater than previously estimated, though it varied with time and location,’ says of Umeå University, the study’s lead author.