Laura Nielsen for Frontier Scientists
Carbon is the building block of life.
Our knowledge of current climate change, however, has us counting how much carbon enters the atmosphere. We burn fossil fuels, adding anthropogenic (human-caused) carbon dioxide to the air. Meanwhile, natural processes also add carbon to the air. We know that methane can arise from warming lakes and oceans. Methane traps heat roughly twenty times as efficiently as does carbon dioxide. Methane and carbon dioxide are also hiding in permafrost, the layers of frozen soil found in very cold places like the Arctic. Permafrost layers can measure up to 5,000 feet thick.
One gigaton equals one million tons. Earth’s current atmosphere holds about 850 gigatons of Carbon. Permafrost is estimated to hold 1,400 gigatons of Carbon.
Permafrost has a misleading name. As our world warms, permafrost that has lasted tens of thousands of years or more is beginning to melt. Sometimes, ancient animals frozen in permafrost reemerge as the permafrost melts. Recently, University of Alaska Fairbanks researchers uncovered the entire skeleton of an extinct steppe bison, bones still connected by ligaments, bearing fur, teeth and hooves. The steppe bison corpse was emerging from thawing permafrost at the bank of a river in Alaska’s North Slope.
The bulk of organic matter found in permafrost, though, is plant matter: roots and leaves which sit in frozen layers of soil where they can’t decay. Although the very top layer of soil in very cold places like the Arctic (the ‘active layer’) freezes and thaws each year, the underlying areas that stay frozen throughout the year are considered true permafrost. Most permafrost was formed during the last Ice Age, the Pleistocene (1,800,000 to 10,000 years ago). Earth ground up by glaciers was deposited over pre-existing soil. Cold temperatures helped freeze the ground into permafrost. Remnants of soil frozen during the Pleistocene can still be found under some of our colder oceans; it is known as subsea permafrost.
The extent of permafrost is changing, though. Warming temperatures tied to climate change are causing shorter winters and heightened temperatures. This reduces Arctic ice cover and warms Arctic soil.
When permafrost thaws, so too does the organic matter it holds. Decaying plant matter is eaten by microorganisms- bacteria which produce carbon dioxide (in the presence of oxygen) or methane (when oxygen is lacking). Those greenhouse gasses are released into the Earth’s atmosphere, contributing to global warming.
Today, the Arctic is still a carbon sink, meaning that the region takes in more carbon than it emits. Plants emit carbon dioxide as they respirate or decompose, but take in carbon dioxide during photosynthesis. The ocean absorbs more carbon than it emits.
Looking forward, though, there may come a tipping point. As permafrost thaws, releasing plant matter to decay and emit carbon dioxide and methane, more greenhouse gasses enter the atmosphere and promote warming. With enough added greenhouse gasses, even more permafrost will melt. This will likely cause a feedback loop, making the Arctic a carbon source instead of a carbon sink.
Thawing permafrost carries other threats. Wildfires become more possible, and large-scale fires also promote atmospheric carbon. Even tundra burns. The water system is altered: where before water was trapped on the surface over the frozen layers of soil, it becomes possible for the water to filter away through the soil. This makes it more difficult for the people, plants and animals relying on Arctic ecosystems. Permafrost changes cause ice heaves and other unusual land action, upsetting roads and buildings that are built on top of permafrost. Sometimes whole villages must be moved away from shore as melting permafrost falls into the sea.
According to the 2012 Arctic Report Card, in Alaska’s North Slope record high temperatures were measured at 20 meters deep within the permafrost layers. While the thickness of the ‘active-layer’ of soil (topsoil which thaws and supports plant life) has not increased much in Alaska’s North Slope, George Washington University permafrost researcher Nikolay Shiklomanov presented at the American Geophysical Union’s Fall Meeting in December of 2012 with the news that the permafrost layer below Barrow, Alaska has thawed so much that the entire area has sunk approximately one foot deeper into the ground.
The importance of monitoring permafrost cannot be underestimated. Systems are in place like the Global Terrestrial Network for Permafrost, to which a station at Lake El’gygytgyn contributes, as well as the National Science Foundation’s Arctic Observing Network and the Circumpolar Active Layer Monitoring Network. Newer technologies allow satellites like NASA’s Aqua satellite to take permafrost measurements from orbit. Meanwhile, some permafrost grids which are measured in the Barrow, Alaska area under the Barrow Arctic Science Consortium have measurement records stretching back to the 1960s.
With the data sets that result, researchers can form more complete climate models on supercomputers. Those models can aid policy makers in understanding the consequences of carbon emissions from permafrost, provide scenarios for the future, and help shape responses.
Vladimir Romanovsky (professor) and Ronald Daanen (assistant professor) of the University of Alaska Fairbanks explain permafrost-created patterns in the Arctic.
International Permafrost Association (IPA) http://ipa.arcticportal.org/
National Oceanic and Atmospheric Administration (NOAA) Arctic Report Card 2012 : Permafrost http://www.arctic.noaa.gov/reportcard/permafrost.html
National Geographic’s GeoPedia : Permafrost http://ngm.nationalgeographic.com/geopedia/Permafrost
National Snow & Ice Data Center (NSIDC) “All About Frozen Ground” http://nsidc.org/cryosphere/frozenground/index.html
National Snow & Ice Data Center (NSIDC) “Atlas of the Cryosphere” http://nsidc.org/cgi-bin/atlas_north