October 10, 2013
The Tundra’s Greenhouse Gas Contribution
Brett Smith for redOrbit.com – Your Universe Online
Arctic tundra is often thought of as a barren wasteland that has no direct bearing on global events. However, a team of Scandinavian scientists is warning that the tundra could be a significant contributor to greenhouse gas emissions if temperatures in the Arctic continue to rise."The soil below the tundra contains very large quantities of carbon – more than twice as much as is present in the planet's entire atmosphere,” explained Magnus Lund, an Arctic researcher from Aarhus University in Denmark. “Therefore, we would like to know if the carbon will stay put – or if it will be released into the atmosphere as CO2 or methane as the climate warms."
Lund is currently working with a team that has been investigating an area in northeast Greenland to determine the amount of carbon released in the form of carbon dioxide as living organisms respire and the amount of carbon being sequestered in plants due to photosynthesis is released. Using this information, the scientists looked to see if the tundra is a source of carbon dioxide or if it acts as a carbon sink, storing it in either living plants or in the peat layer.
"We can see that the annual release of CO2 from living organisms increases linearly as the temperature increases, measured as the average temperature in July,” Lund said. “However, it seems that the ability of the photosynthesis to assimilate carbon stops increasing when the temperature in July rises above approx. seven degrees Celsius, which has occurred several times in past years. This means that the tundra may become a CO2 source if the current strong climate warming continues as expected.”
Lund admitted that his team’s assessment is based on limited number of measurements.
"It's a problem in the Arctic that we don't perform measurements at enough locations,” Lund continued. “The variation between locations is substantial both for CO2 and not least for methane. In Greenland, we measure near Nuuk and in Zackenberg, where we collect measurements from a relatively dry heath and from a moist fen area. A new station is also being established at Station Nord in the northernmost part of Greenland."
In the team’s most recent academic paper, published earlier this year in Biogeosciences, they emphasized the danger posed by the tundra’s release of the greenhouse gas methane. In the study, the researchers noted that when the tundra freezes and ice is formed on the surface, large amounts of methane are released. An extremely powerful greenhouse gas, methane’s greenhouse effect is 20-25 times as strong as that of carbon dioxide.
Other studies have indicated that the formation of methane is related to the tundra's water content – the more water in the tundra, the more methane is formed. Where there is less water, oxygen provides the basis for formation of carbon dioxide. The net result is that areas that dry out will have increased carbon dioxide emissions, while areas that become wetter will release more methane. The amount of water in the tundra is affected by temperature and precipitation, but also by how much ice is in the soil.
The researchers said they are currently working to establish how and when the tundra’s methane release is formed, and if this involves new or old carbon sources.