Thawing permafrost in high-altitude mountains may be contributing to atmospheric carbon dioxide emissions without scientists having realised, the latest research showed.
High altitude Alpine-rich mountain ranges in Colorado are emitting more CO2 than it captures annually, new research shows.
This is potentially creating a feedback loop that could increase climate warming and lead to more CO2 emissions.
A similar phenomenon exists in the Arctic, where research in recent decades has shown that melting permafrost is unearthing long-frozen tundra soil and releasing CO2 reserves buried for centuries.
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Denali is the centerpiece of Denali National Park, a sprawling expanse of forestland, tundra, glaciers and snowy peaks. Each year about 1,100 people try to reach its summit at 20,310 feet (6,190 meters)
John Knowles, lead author of the new study in CU Boulder’s Department of Geography and a researcher at the Institute of Arctic and Alpine Research said: ‘We wondered if the same thing could be happening in alpine terrain.’
‘This study is a strong indication that that is indeed the case.’
Forests have long been considered vital carbon ‘sinks,’ sequestering more carbon than they produce and helping to mitigate global CO2 levels.
As part of the Earth’s carbon cycle, trees and other vegetation absorb CO2 via photosynthesis while microbes emit it back to the atmosphere via respiration, just as humans release CO2 while breathing.
The Alpine Tundra Ecosystem at the Colorado Front Range of the Rocky Mountains starts between elevations of 11,000 to 11,500 feet.
Strong, frequent winds and cold temperatures limit what plants can grow there.
Melting permafrost, however, changes that process.
As previously frozen tundra soil thaws and becomes exposed for the first time in years, its nutrients become freshly available for microbes to consume.
Unlike plants, which go dormant in winter, microscopic organisms can feast all year long if environmental conditions are right.
To study this effect in alpine conditions, researchers measured the surface-to-air CO2 transfer over seven consecutive years from 2008 to 2014 at the Niwot Ridge Long Term Ecological Research (LTER) site in Colorado, a high-altitude research project that has been in continuous operation for over 35 years.
The team also collected samples of soil CO2 and used radiocarbon dating to estimate how long the carbon forming that CO2 had been present in the landscape.
The study showed, somewhat surprisingly, that barren, wind-scoured tundra landscapes above 11,000 feet emitted more CO2 than they captured each year, and that a fraction of that CO2 was relatively old during the winter, the first such finding of its kind in temperate latitudes.
The findings suggest higher-than-expected year-round microbial activity, even in the absence of a deep insulating snowpack.
For more than a decade, the National Park Service has required that climbers keep waste off the Alaska mountain’s surface. Mountaineers captured their poop in biodegradable bags held by portable toilets and pitched it into deep crevasses on the glacier. A view of Mount Denali
‘Microbes need it to be not too cold and not too dry, they need liquid water,’ said Knowles, now a researcher at the University of Arizona.
‘The surprise here is that we show winter microbial activity persisting in permafrost areas that don’t collect much insulating snowpack due to wind stripping it away.’
While the alpine tundra’s net CO2 contributions are small compared to a forest’s sequestration capability, the newly-documented effect may act as something of a counterweight, hampering atmospheric CO2 reductions from mountain ecosystems in general. The findings will need to be factored in to future projections of global warming, Knowles said.
‘Until now, little was known about how alpine tundra behaved with regard to this balance, and especially how it could continue emitting CO2 year after year’ Knowles said.
‘But now, we have evidence that climate change or another disturbance may be liberating decades-to-centuries-old carbon from this landscape.’
The full report can be found in the journal
WHAT IS PERMAFROST AND WHAT HAPPENS IF IT MELTS?
Permafrost is a permanently frozen layer below the Earth’s surface found in Arctic regions such as Alaska, Siberia and Canada.
It typically consists of soil, gravel and sand bound together by ice, and is classified as ground that has remained below 0°C (32°F) for at least two years.
It is estimated 1,500 billion tons of carbon is stored in the world’s permafrost – more than twice the amount found in the atmosphere.
The carbon comes in the form of ancient vegetation and soil that has remained frozen for millennia.
If global warming were to melt the world’s permafrost, it could release thousands of tonnes of carbon dioxide and methane into the atmosphere.
Because some permafrost regions have stayed frozen for thousands of years, it is of particular interest for scientists.
Ancient remains found in permafrost are among the most complete ever found because the ice stops organic matter from decomposing.
A number of 2,500-year-old bodies buried in Siberia by a group of nomads known as the Scythians have been found with their tattooed skin still intact.
A baby mammoth corpse uncovered on Russia’s Arctic coast in 2010 still sported clumps of its hair despite being more than 39,000 years old.
Permafrost is also used in the study of Earth’s geological history as soil and minerals buried deep in Arctic regions for thousands of years can be dug up and studied today.