A Nitrous Oxide Blast
Published in The EarthSphere Blog. Cover Image: The Arctic Carbon Bomb (by ArcheanArt — Modified from a NASA public domain photo)
Travel far enough north, and you will find yourself in the Arctic, a geographical region named after the Greek word for bear. Sixty percent of the Arctic is ocean, and the remaining 40 percent largely consists of the northern edges of multiple countries bordering on the Arctic Ocean. About four million people live in the Arctic, and its largest city is Murmansk, Russia, with about 300,000 residents. The Arctic is also home to Yedoma, a highly organic, Pleistocene-age permafrost containing 50 to 90 percent ice mixed with organic carbon. When Yedoma melts, it delivers a blast of potent greenhouse gases to the atmosphere.
Large deposits of Yedoma cover eastern Siberia and western Alaska. These deposits cover over a million square kilometers. Yedoma differs from other permafrost due to its very high water content, large continuous areal extent, and greater thickness (meaning larger volumes of organic carbon). All these characteristics combine to make Yedoma very susceptible to rapid melting and massive releases of greenhouse gases.
Most references to Yedoma also include the lake-filled thermokarst landscapes that develop when Yedoma degrades. Repeated thawing and refreezing of Yedoma deposits creates a terrain with low hills and shallow depressions, called ‘alas,’ filled with meltwater. As Yedoma melts, it becomes a powerful part of the Arctic carbon bomb.
The Carbon Bomb
The term solid ground takes on a new meaning in the context of permafrost. This ice-hardened earth and soil mixture is rock solid until temperatures rise above freezing. Then it turns into a festering, organic goo containing the rotting remains of plants and animals that lived thousands of years ago. Permafrost underlies much of the land within the Arctic circle and 24 percent of the land in the northern hemisphere. Over time, it has morphed from an engineering problem into a climate change problem.
Permafrost forms over centuries. During that time, plants and animals live and die with their remains frozen into the structure of the soil before complete decomposition set in. The normal carbon cycle is interrupted by this process. Plants and animals require carbon to live, and they sequester this carbon in their bodies. Under most circumstances, their death starts a process where bacteria break down the organic material and release carbon back into the atmosphere as carbon dioxide and methane. Permafrost creates a time capsule where decomposition is interrupted, and the carbon remains sequestered in the icy soil.
An estimated 1,400 gigatons of carbon lie frozen in the Arctic permafrost. By comparison, the earth’s atmosphere contains only 850 gigatons of carbon. Yedoma deposits contain over 130 gigatons of carbon. As the Arctic reaches a tipping point, Yedoma carbon may be the first blast of greenhouse gases released back into the atmosphere. Scientists have long recognized the high carbon dioxide and methane potential of melting Yedoma, but new research shows these deposits are potent producers of nitrous oxide (N2O), another powerful greenhouse gas.
Yedoma and Nitrous Oxide
Nitrous oxide is the third most prominent greenhouse gas contributing to global warming. One ton of N2O has the same warming potential as about 300 tons of CO2. Burning fossil fuels is not at the heart of the N2O problem. Agriculture is the main culprit, accounting for roughly three-quarters of all N2O emissions.
Nitrous Oxide packs quite a punch. The problem of nitrous oxide emissions has been generally ignored in our efforts to combat climate change, even though we have seen a 30% increase in N2O emissions over the past four decades. The main culprit for rising N2O emissions is a global addiction to synthetic nitrogen fertilizer. But it is easier to make large oil companies the bad guys than point the finger at farmers, so we don’t often talk about the N2O problem.
Set against this background, research showing Yedoma as a massive new source of nitrous oxide is not good news. The problem is related to the high ice content of Yedoma, making it prone to rapid thawing. Typically, the natural nitrogen cycle in cold Arctic soils moves slowly. But when thawing is too rapid, the population of microbes producing N2O grows, and the N2O consuming populations shrink. This imbalance leads to excess nitrous oxide that dissipates into the atmosphere.
The Arctic is warming considerably faster than the rest of the planet, increasing the probability of the region reaching a tipping point where natural processes, not fossil fuel emissions, release enough greenhouse gases to perpetuate the permafrost melt. By definition, human intervention becomes impossible after reaching the tipping point, and the process continues until all 1,400 gigatons of Arctic Carbon become atmospheric carbon. Under these circumstances, pumping more Yedoma-generated nitrous oxide into the Arctic air only speeds up the permafrost melting rate.
The Arctic may end up being one of the largest future contributors to greenhouse gases and global warming.
Related Stories:
Nitrous Oxide, The Shunned Stepchild of the Greenhouse Gas Family — CO2, Methane, and The Other One (by WM House; ArcheanWeb; Medium)
Permafrost: A ticking carbon bomb (by WM House; ArcheanWeb)
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Sources:
Basic information about the Arctic (Source: Arctic Centre)
Yedoma (Source: NSIDC)
Deep Yedoma permafrost: A synthesis of depositional characteristics and carbon vulnerability (by Jens Strauss, Lutz Schirrmeister, Guido Grosse, Daniel Fortier, Gustaf Hugelius, Christian Knoblauch, Vladimir Romanovsky, Christina Schädel, Thomas Schneider von Deimling, Edward A.G.Schuur, Denis Shmelev, Mathias Ulrich, Alexandra Veremeeva; Science Direct)
Scientists Find a New Source of a Greenhouse Gas Emissions in The Siberian Permafrost (by David Nield; Science Alert)
All About Frozen Ground (Source: NSIDC)
