Nav: Home

Early spring rain boosts methane from thawing permafrost by 30 percent

February 04, 2019

Arctic permafrost is thawing as the Earth warms due to climate change. In some cases, scientists predict that this thawing soil will release increasing amounts of methane, a potent greenhouse gas, that is known to trap more heat in our planet's atmosphere.

Now a University of Washington-led team has found a new reason behind increased methane emissions from a thawing permafrost bog in Alaska: Early spring rainfall warms up the bog and promotes the growth of plants and methane-producing microbes. The team showed that early precipitation in 2016 warmed the bog about three weeks earlier than usual, and increased the bog's methane emissions by 30 percent compared to previous years. These results were recently published in Geophysical Research Letters.

"In general, the chance of generating methane goes up with increased rainfall because soils get waterlogged. But what we see here is different," said corresponding author Rebecca Neumann, an associate professor in the UW Department of Civil & Environmental Engineering. "Early rainfall sent a slog of warm water moving into our bog. We believe microbes in the bog got excited because they were warmed up, so they released nutrients from the soil that allowed more plant growth. Methane production and emission are tightly linked with soil temperature and plant growth.

"Our results emphasize that these permafrost regions are sensitive to the thermal effects of rain, and because we're anticipating that these environments are going to get wetter in the future, we could be seeing increases in methane emissions that we weren't expecting."

In northern latitudes, bogs form when ice-rich permafrost thaws. The thawed area sinks relative to the surrounding landscape as the ice melts, and soil becomes waterlogged, creating a wetland with grassy plants called sedges growing across the surface.

Neumann and her team studied a thawing permafrost bog located about 20 miles from Fairbanks, Alaska, from 2014 through 2016. Over the years, the researchers tracked methane emissions in and around the bog, sedge plant growth and soil temperature at 16 different depths.

In 2016 the team saw temperatures at the edge of the bog increase 20 days earlier, and cumulative methane emissions across the bog increase by 30 percent as compared to the previous years.

"We saw the plants going crazy and methane emissions going bonkers," Neumann said. "2016 had above average rainfall, but so did 2014. So what was different about this year?"

The key turned out to be the timing of the precipitation: The spring rainfall started earlier in 2016 compared to 2014. In the spring the ground is colder than the air. So the rain, which is the same temperature as the air, warms up the ground as it enters the soil. The earlier the spring rains come, the sooner the soil in the surrounding forest gets saturated. Any surplus rain then flows down into the bog, rapidly warming the bog soils.

The warm soil aids microbes living in the bog and speeds up their metabolisms. Normally microbes use oxygen to break down organic matter, and they release carbon dioxide into the air. But in waterlogged soils, like a bog created by permafrost thaw, there's no oxygen around. So the microbes have to use whatever is available, and they end up converting organic matter into methane.

"It's the bottom of the barrel in terms of energy production for them," Neumann said. "The microbes in this bog on some level are like 'Oh man, we're stuck making methane because that's all this bog is allowing us to do.'"

At the same time, the sedge plants are also fueled by the warmer soil. In 2016 the team found more of these plants at the warmer edges of the bog. Sedges, like most plants, take carbon dioxide from the air to make their food, which they send to their roots to help them grow. Sometimes the food leaks out of the roots into the soil where it can become food for the microbes. So more sedges directly fuel the microbes to make more methane.

In addition, sedges contain hollow, air-filled tubes that allow oxygen to flow from the air to their roots. These tubes also allow the microbes' methane to escape the bog and enter the atmosphere.

"The plants are really doing two things," Neumann said. "They're providing yummy carbon that lets the microbes make more methane than they would have otherwise. The plants also provide a conduit that allows methane to escape into the atmosphere. They're a double whammy for methane production and emission."

As the Earth warms, these northern latitude regions are expected to experience more rainfall. If this rain falls in spring or early summer, these areas could release more methane into the atmosphere than is currently predicted. Neumann and her team plan to examine methane emissions from other bogs to see if this pattern holds true across northern latitudes.

"In general, the ability of rain to transport thermal energy into soils has been underappreciated," Neumann said. "Our study shows that by affecting soil temperature and methane emissions, rain can increase the ability of thawing permafrost landscapes to warm the climate."
-end-
Co-authors include Colby Moorberg at Kansas State University, who conducted this work as a UW civil and environmental engineering postdoctoral researcher; Jessica Lundquist at the UW; Jesse Turner at SMRU consulting, who conducted this work as a field technician after completing a UW oceanography undergraduate degree; Mark Waldrop and Jack McFarland at the U.S. Geological Survey; Eugénie Euskirchen and Colin Edgar at the University of Alaska Fairbanks; and Merritt Turetsky at the University of Guelph. This research was funded by the U.S. Department of Energy Office of Science and the USGS Land Change Science Program.

For more information, contact Neumann at rbneum@uw.edu.

Grant numbers: DE-SC0010338

Photos/video available (copy and paste link into browser if clicking the hyperlink doesn't work): https://drive.google.com/drive/folders/1dI8pe16zuRSYcCyvcG4U4jyJzJbILjIP?usp=sharing

Posted online at: http://www.washington.edu/news/2019/02/04/early-rainfall-increases-methane-from-thaw-bog/

University of Washington

Related Climate Change Articles:

Mapping the path of climate change
Predicting a major transition, such as climate change, is extremely difficult, but the probabilistic framework developed by the authors is the first step in identifying the path between a shift in two environmental states.
Small change for climate change: Time to increase research funding to save the world
A new study shows that there is a huge disproportion in the level of funding for social science research into the greatest challenge in combating global warming -- how to get individuals and societies to overcome ingrained human habits to make the changes necessary to mitigate climate change.
Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.
Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.
A CERN for climate change
In a Perspective article appearing in this week's Proceedings of the National Academy of Sciences, Tim Palmer (Oxford University), and Bjorn Stevens (Max Planck Society), critically reflect on the present state of Earth system modelling.
Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).
Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.
Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.
Could climate change cause infertility?
A number of plant and animal species could find it increasingly difficult to reproduce if climate change worsens and global temperatures become more extreme -- a stark warning highlighted by new scientific research.
Predicting climate change
Thomas Crowther, ETH Zurich identifies long-disappeared forests available for restoration across the world.
More Climate Change News and Climate Change Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.