Methane burps

Small Temperature Bumps Can Cause Big Arctic Methane Burps

Warming can encourage the growth of microbes in permafrost that produce more greenhouse gases

ScientificAmerican,

10 July, 2019

As temperatures rise in the rapidly warming Arctic, scientists are growing more and more concerned about the region’s permafrost—the carbon-rich, frozen soil that covers much of the landscape. As permafrost warms up and begins to thaw out, microbes in the soil may release large quantities of both climate-warming carbon dioxide and methane into the atmosphere, potentially worsening the effects of climate change.

Researchers are carefully monitoring the natural emissions from permafrost in the Arctic. And in recent years, they’ve also begun designing their own experiments aimed at investigating the way the frozen soil might react to future climate change.

They’re finding that even a little bit of warming may cause permafrost to release significantly higher levels of greenhouse gases into the air.

New results from one of these studies, published yesterday in Proceedings of the National Academy of Sciences, suggest that the microbe communities are the key. Warming can alter the types of organisms that live and thrive in the frozen soil, favoring microbes that tend to produce more methane and carbon dioxide.

The new study relied on experiments from a special research site in Alaska, where scientists have designed a way to manipulate the natural landscape to investigate the effects of rising temperatures. They’ve built special fences that allow snow to pile up deeper on the ground, forming a kind of insulation and causing the permafrost below the surface to warm up. Permafrost at the experimental sites was around a degree Celsius warmer than nearby sites that hadn’t been insulated.

The research site—known as the Carbon in Permafrost Experimental Heating Project—provides a unique opportunity to simulate the effects of future climate change. In a laboratory setting, it might be more difficult to exactly reconstruct the natural landscape, making scientists less sure of their results.

For the new study, the researchers conducted special forms of genetic sequencing to determine how microbe communities changed in the warmer plots. The shifts were apparent after less than five years of elevated temperatures.

In shallower layers of the soil, they found an increase in microbes that produce more carbon dioxide. And in deeper layers, they found an increase in microbes that produce larger amounts of methane, an even more potent greenhouse gas. At the same time, methane emissions from the experimental sites also increased.

The methane-producing microbes are a particular concern, the researchers note. Both carbon dioxide and methane have a warming effect on the climate—but if a greater proportion of the soil’s greenhouse gas emissions shift to methane, the stronger of the two gases, then the permafrost’s effect on the climate could be even more powerful than scientists currently anticipate.

The study provides experimental support for scientists’ ongoing fears about thawing permafrost. Throughout the Arctic, researchers are finding that large swaths of frozen soil are steadily heating up, sometimes faster than scientists had previously predicted.

The research also underscores a growing scientific interest in the links between climate change and the world’s tiniest organisms.

Just last month, a group of more than 30 scientists jointly published a statement warning of the many ways that climate change may affect microbe communities, and the ways that microbes may in turn affect the progression of global warming.

In addition to permafrost, they pointed to changes in microbe communities that affect the ocean’s carbon uptake and the marine food web, lead to algae blooms, alter the growth of vegetation, influence agricultural production, and contribute to the spread of infectious diseases.

The statement “documents the central role and global importance of microorganisms in climate change biology,” the authors write. “It also puts humanity on notice that the impact of climate change will depend heavily on responses of microorganisms, which are essential for achieving an environmentally sustainable future.”