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Part of Earth is always frozen and acts as a giant refrigerator for carbon

7 de January 2021

The price of homes is falling sharply in some northern regions of the planet. Why? Because the seemingly permanently frozen ground they were built on is now thawing. This has much more far-reaching implications for the climate, and could even spell defeat in the battle against global warming.

Warming is a problem for the coldest, most remote communities. Photo: Unsplash/Public Domain.

Warming is a problem for the coldest, most remote communities. Photo: Unsplash/Public Domain.

Three intrepid researchers from CREAF and the Autonomous University of Barcelona, Olga Margalef, Oriol Grau and Sergi Pla, have undertaken two expeditions to some of the world’s frozen territories in recent years, to learn more about the devastating consequences of thawing and work out how to mitigate them. Their first expedition was to Sweden in 2018, and the second to Alaska in 2019. “Global warming is causing the degradation of the Arctic countries’ frozen ground, the boundaries of which have receded by around 30 to 80 km,” says Olga. “Studying the thawing of such ground is vital to understand the changes it could bring about worldwide, including, for instance, huce CO2 emissions and the release of phosphorus and nitrogen,” she adds.

Toolik (Alaska), 2019. Frozen ground is as hard as rock, so sampling it is not easy and requires a powerful drilling machine. The one the researchers used was designed specifically for their work and fitted with a motor. The region’s frozen ground was completely continuous. Photo: CREAF.

Abisko (Sweden), 2018. A soil core that Olga and Oriol extracted while sampling discontinuous frozen ground, in which ice forms lentil-like spots. The researchers used specialized tools to take samples of soil and the frozen plants it contained from a range of depths. They found evidence of ice boundaries having merged recently, a sign of previous thawing. The samples taken from the greatest depths will make it possible to reconstruct the environmental conditions the region has experienced over no fewer than the last 9000 years. This will enable the research team to study the climate changes that have occurred in that time and compare them to the one taking place at present. Photo: CREAF.

An ice cube in the atmosphere’s hands (for the time being)

When you pick up an ice cube, it quickly reacts to the warmth of your hands, melting into water. The same thing is happening to Earth’s ice; it is melting in the increasingly warm atmosphere around it. Fortunately, the planet still has some ground that stays frozen all year round. That ground is called permafrost.

Approximately 23 million km2 of the Northern Hemisphere consist of permafrost with an active layer, an area more than twice the size of the USA.

Permafrost is a thick layer of up to a kilometre in depth, in which there is virtually no life. Consequently, the organic matter, carbon, nitrogen and phosphorus it contains are left intact, preserved as if in a refrigerator. On top of the permafrost there is an active layer that freezes in winter and thaws in summer, and in which biological activity does take place. Approximately 23 million km2 of the Northern Hemisphere consist of permafrost with an active layer, an area more than twice the size of the USA.

Structure of ecosystems with permafrost. A talik is unfrozen ground in a permafrost area. Taliks are often found below lakes, whose very high level of thermal conductivity helps the ground beneath them thaw in summer. Figure: Pidwirny, M (2006), Periglacial Processes and Landforms (Fundamentals of Physical Geography).

Alarmingly, global warming is beginning to affect permafrost and could cause it to stop acting as a refrigerator. If that were to happen, the permafrost’s organic matter would decompose and the vast amount of carbon and nutrients stored in it would be released as gases (including CO2), diluted in watercourses or absorbed by living organisms. Nobody yet knows what the exact consequences of permafrost melt will be, but the threat it poses is evident. Some experts have even warned of a potential tipping point in the fight against climate change.

Peatlands account for almost half the carbon stored in the ground throughout the world, despite covering just 3% of its surface.

Luckily, as the United Nations Environment Programme’s Frontiers 2018/19 report on emerging issues of environmental concern clearly reflects, there is growing global awareness of the ecological importance of permafrost. The report in question and the Paris Agreement both call for policies for the protection of permafrost and, in general, of peatlands, where the greatest concentrations of carbon in cold ground lie.

Peatlands help combat climate chang

Also known as bogs, mires and fens, peatlands are (generally acidic) wetlands whose soil receives little oxygen and contains a large volume (over 30%) of organic matter called peat, which comes from the vascular plants, moss and lichens typical of cold climates. Because peatlands are waterlogged and oxygen-starved, their organic matter is preserved or decomposes very slowly. Consequently, the planet’s peatlands contain over 220 Gt of carbon (almost half the carbon stored in the ground worldwide) despite covering just 3% of its surface.

There are peatlands (or mires) everywhere from Asia and Europe to the tropics, but they are most common in cold regions. In Catalonia, for example, peatlands can be found in the high-lying mountain areas of the Pyrenees. Figure: Lappalainen, E. (1996). Global peat resources.

The regions with the largest proportions of peatlands are those that are completely frozen, such as the Arctic and the subarctic zone, where permafrost is also found. Scientists have calculated that, in total, Earth has more than 1.4 million km2 of permafrost peatlands with a peat layer thicker than 40 cm. If such peatlands were to lose their water, due to thawing or agricultural activity, the peat preserved in them would dry out and come into contact with oxygen, and the organic matter would begin to decompose, emitting huge quantities of CO2 into the atmosphere, like thousands of factories in full swing.

It is therefore essential that we understand how such Arctic and subarctic ecosystems work, and that is why CREAF sends researchers to study them at first hand (despite the risk of them becoming part of the ice cube!).

Alaska, 2019. Olga Margalef up to her elbows (in every sense) in a bog. Photo: CREAF.

Alaska, 2019. Sergi Pla taking notes. The researchers reported that their second field campaign was much harder than the first, owing to colder temperatures and frequent heavy rain and snow, not to mention a two-and-a-half-hour slog from the research station to the sampling area. Photo: CREAF.

Alaska, 2019. Study area in Toolik. Polygonal peatlands are common in this region and cover large expanses of the Arctic. Their formation is the result of rapid temperature falls in winter causing cracks in the surface of the permafrost, producing ice wedges with a geometric pattern. Due to their shape, these peatlands have very different hydrological, temperature and vegetation conditions at their edges and at their centre. The degradation of the edges is clear to see.

 

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SciComm at CREAF since 2016. Nature and outreach lover. Biologist (University of Barcelona) and Science Communication master (Barcelona School of Management - UPF).
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