Early Spring Rain Boosts Methane Release From Melting Permafrost By 30%
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?”
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https://desdemonadespair.net/2019/02/early-spring-rain-boosts-methane-from-thawing-permafrost-by-30-percent-permafrost-regions-are-sensitive-to-the-thermal-effects-of-rain.html