The strong binding of organic matter that originates from dead plant residues to soil mineral particles in the polar regions is becoming more fragile than before due to climate change and rising temperatures that cause ice to melt, a new study warns.
Previously, researchers had referred to organic carbon stores found in ice-rich Arctic permafrost as more difficult for microorganisms to use due to the freezing state.
In the study, published April 13 in the journal Nature Communications, the authors note that because temperatures are soaring in the Arctic, this huge freezer is melting rapidly, and the old carbon stored in it can now be decomposed by microorganisms, releasing carbon dioxide and methane into the atmosphere.
One of the ice cores in Siberia that was examined by researchers (Lotus Schermaitzer - University of Cologne)
Permafrost
Permafrost is any soil, sediment, or rock that remains frozen for at least two years. For decades, people have treated the frozen earth as strong and largely immobile. Industries and infrastructure were built on top of the hardness of this soil, and buried their waste inside. In some places, scientists and others have used permafrost to store radioactive waste.
Permafrost covers vast areas of land, including about a quarter of the northern hemisphere's land area. Although the ground is freezing, permafrost areas are not always covered with snow. As the Arctic warms up about 4 times faster than the rest of the planet as a result of climate change, up to 65% of the region's permafrost could disappear by 2100.
Yannick Martinez, lead author of the study and postdoctoral research fellow at the Institute of Geology and Mineralogy at the University of Cologne in Germany, and the Columbia University School of Climate, says accurate predictions of greenhouse gas emissions from permafrost deposits are more complex than previously assumed, given that the microbial decomposition of organic matter in sediments has varied greatly over the past 55,<> years. This is due to different climatic conditions during this long period of deposition.
Martins added – in a statement to Al Jazeera Net – that most of the Arctic region is covered with permafrost, and contains large amounts of carbon – almost twice the amount of carbon in the atmosphere – but these large amounts of carbon are prone to release into the atmosphere due to the acceleration of rising temperatures in the Arctic and melting ice.
A piece of excavated permafrost pulp extracted during excavations in Siberia (Lotus Schermaitzer - University of Cologne)
Carbon decomposition
According to the study's lead author, ancient carbon stored in ice can now be degraded by microorganisms, releasing carbon dioxide and methane into the atmosphere. These greenhouse gases are accelerating global warming. The higher the temperature, the more greenhouse gases are released from the permafrost, causing temperatures to rise further and sediment to freeze faster.
The researchers studied the long permafrost cores from the Arctic in Siberia. These cores come from ice-rich, fine-grained deposits deposited in large areas of Siberia and Alaska during the last ice age.
The nuclei, which are up to 12 meters long, are made up of deposits that have accumulated over a period of up to 55,<> years, according to a press release published on the website "Viz.org" (Phys.org).
The results of analyses of permafrost cores show that a large part of the carbon binds to metal molecules and is therefore difficult to reach for microorganisms. Warter, wetter conditions also led to a weak binding of carbon to metal particles, while a colder and drier climate led to a stronger bonding, mainly to iron oxides. A stronger binding to iron oxides means that the decomposition rates of older plant material are lower.