It is very clear that the Arctic is warming rapidly, and frozen soil begin to melt, often for the first time in thousands of years. But as it happens, as a muddy, dirt, which flows with the permafrost, when the ice melts.
As the temperature of the earth rises above the freezing point, the microorganisms decompose the organic matter in the soil. Greenhouse gases – including carbon dioxide, methane and nitrous oxide – released into the atmosphere, accelerating global warming. Soils hold twice as much carbon in the permafrost zone, than the atmosphere does – almost 1,600 billion tonnes1.
What part of that is to decompose? It will be released suddenly or slowly leak out? We have to find out.
Current models of release of greenhouse gases and climate believed that frost thaws progressively from the surface downwards. The deeper layers of the organic substances are subjected to for decades or even centuries, and some models are beginning to track the slow changes.
But models ignore an even more disturbing problem. Frozen soil is not only to lock carbon – it is physically holds the landscape together. Throughout the Arctic and northern regions, permafrost collapses suddenly, as the ice melts pockets in it. Instead of a few centimeters of soil thawing of each year, a few meters of soil could be destabilizing for a few days or weeks. The land may sink and be flooded by swelling the lakes and marshes.
The sudden melting of permafrost & # 39 is a dramatic look. Returning to the field sites in Alaska, for example, we often find that the land that had been forested year ago, is now covered with lakes2, Cancers, who once ran clear, thick with sediment. Slopes are thinning, sometimes taking sensitive scientific equipment with them.
This type of thawing with & # 39; is a serious & # 39; oznay problem for the communities living around the Arctic (see «Arctic permafrost"). buckle roads, houses become unstable. Access to traditional food varies, because it becomes dangerous to travel across the country to hunt. Seven & # 39; and can not reach the line gaming traps that supported them for many generations.
In short, the permafrost thaws much faster than the models predicted, with unknown consequences for the greenhouse gas issue. Researchers urgently need to learn more about it. Here we describe how.
Permafrost Permafrost. It consists of the soil, rocks or sediments, often with large chunks of ice mixed. About a quarter of the land in the Northern Hemisphere & # 39; and frozen in this way. Carbon built in these frozen ground for thousands of years, since the organic material from dead plants, animals and microorganisms, not broken.
Designers try to project how much of this carbon will be released when the permafrost thaws. It is difficult, for example, they need to understand how much carbon in the air is absorbed by plants and returned to the soil, replenishing some of what was lost. Projections indicate that the slow and steady thawing to release about 200 billion tons of carbon over the next 300 years of business as usual scenario, warming3, This is equivalent to approximately 15% of soil carbon currently stocked in the frozen north.
But it may be underestimated. About 20% of the frozen lands have features that increase the likelihood of a sharp melting, for example, a large amount of ice in the ground or on unstable slopes2, Where the permafrost thaws rapidly and erratically, causing landslides and rapid erosion. Forests can be flooded, killing large areas of trees. Lakes that have existed for many generations may disappear, or the water can be diverted.
To make matters worse, the most unstable regions also tend to be the most carbon-rich2, For example, 1 million square kilometers of Siberia, Canada and Alaska contain pockets of Edom – thick permafrost deposits from the last ice age4, These deposits often & # 39 are 90% of the ice, making them extremely vulnerable to warming. Furthermore, due to dust and ice pastures that were prepared when the deposits are formed, Ed contains 130 billion tons of organic carbon – equivalent to more than ten years of global emission of greenhouse gases human.
How much permafrost carbon could be released with a sharp melting? As a first step, this year we have synthesized the results of published studies sharp melting across the permafrost zone. We asked how this type of thawing effect on plants, soil and moisture in the soil. Studies have revealed a pattern of decay and regeneration. This international project was supported Permafrost Carbon Network (www.permafrostcarbon.org), part of the multi-million dollar global study of environmental change in the Arctic (search).
Lakes and marshes with & # 39 are the largest part of the problem because they produce large amounts of methane, a greenhouse gas that with 39 & # is much more potent than CO25, Erosion of the hills and mountains is also problematic: if the slopes of the mountains to melt and break up, many CO2 is released as the material is destabilized, decompose or washed in streams or rivers6.
We believe that the rapid melting of permafrost in lowland lakes and marshes, as well as that in the mountainous hills, can liberate from 60 billion to 100 billion tons of carbon 2300. This is in addition to the 200 billion tons of carbon is expected to be released in other regions that will gradually thaw. Although dramatic melting of permafrost will be less than 20% of the frozen ground, it increases the permafrost carbon release projections by about 50%. Gradual melting effect on the surface of the frozen ground and slowly filters down. Sudden collapse releases more carbon per square meter, because it destroys the stocks of deep frozen layers.
In addition, since a sharp melting releases more methane than the gradual thawing it makes an impact on the climate of the two processes will be similar7So, together, the effects of thawing permafrost on Earth's climate can be twice more than expected from the current models.
It stabilizes the climate at a temperature of 1,5 ° C warming8 It requires massive reductions in carbon emissions due to human activities; additional carbon emissions from the melting of the Arctic make it even more urgent.
Our assessment & # 39 are indicative and require treatment. However, they show that the understanding of the sharp melting must be scientific priority.
Firstly, climatic and soil scientists need to find out where the highest methane and CO2 will come from. Although we have a good grasp of the current issues thaw lakes and marshes9And how much there was in the past10We need to be able to project, which will be from & # 39; to appear new. We also need to know how fast they drain as the climate warms.
Second, the erosion of the soil thawed on the slopes poorly understood. Since the collapsed slopes are difficult to detect by satellite, only a few large studies have been made, often using intelligence or road oil surveys. Researchers should determine how much carbon is shifting permafrost and what happens after it is thawed. For example, it is not known how much it would be in the earth or to be buried, and how much will enter the atmosphere as a greenhouse gas11.12, And what happens with this material as it flows in rivers, lakes and estuaries?
Third, we need to determine the extent to which plant growth will offset the carbon that is released permafrost3Over time, the lake captured wetland plants, and ultimately to drain and convert it back to the tundra. Eroded areas populated by plants, which helps stabilize the soil and speed up their recovery. Researchers should monitor how thawed ecosystem develops, the rate at which vegetation stabilizes, and how these plants accumulate biomass. Vegetation also reacts increased CO2 and nutrients, increased length of growing season and changes in soil moisture levels. Designers have to anticipate change feedbacks between ecological communities and geomorphology as the transformation of permafrost landscapes.
Fourthly, the distribution of the ice in the soil with & # 39 is the main factor influencing the fate eternal carbon permafrost. However, observations of underground ice a few. More common geophysical measurements could map pockets under the surface of the ice, revealing where it is concentrated and how quickly it melts. machine learning techniques can even be designed to predict where most ice is buried by analyzing the soil and topography on the surface.
the following steps
In order to connect these gaps in our knowledge, we have five recommendations.
Expansion of measurement technology. There needs to be better monitoring of permafrost and carbon through the Arctic, particularly in the regions affected by a sharp thaw. It is important to set the initial conditions of permafrost and the alteration of ecosystems, for which can be compared to future actions. This will require the aircraft on the basis of the leader (light detection and ranging, geodetic method that uses pulsed laser light), unmanned based on a survey and the best algorithms for image analysis.
Monitoring units of the Fund. river chemistry can be a sensitive indicator of the sharp melting, but many monitoring stations are being abandoned13, Instead, it is necessary to increase the national and international investment in long-term sites that refer to the observations of the land with the water and marine measurements. Best Entries of organic matter and nutrients in rivers would shed light on the plants and permafrost microbial communities respond to the steep and gradual thawing.
Collection of additional data. Regions that are prone to rapid melting need more wells, long-term observatory and experimentation. Field measurements have to quantify how much CO2 and methane is discharged into the atmosphere is broken, and recovered in the form of frozen soil. It is important to note that the permafrost researchers and industrial groups have to make all the data on the Earth's surface of ice – even if the information from the & # 39 is a qualitative – in the state archives.
Construction of an integrated model. Earth-system model should include key processes affecting the release of carbon permafrost – including how the temperature and moisture effect release of carbon for a number of plant and climate scenarios. Since sharp melting occurs in the small spatial scale, detailed model of the process of this dynamic can be impractical to run directly into the earth system model. Scaffolds should be designed to understand and quantify the impact of these small-scale processes at the global level.
Improve reporting. Policymakers need better evaluation of the current impact of a sharp melting on climate change. It should be considered as part of the set of unresolved climate feedbacks, as the Intergovernmental Panel on Climate Change (IPCC), made for a gradual thaw in the 2018 special report8, Carbon Network permafrost contributes to such efforts, for example, by ensuring that a sharp melting characterized by the IPCC Special Report on the ocean and the cryosphere to climate changeWhich will be released later this year.
We can not prevent a sharp melting permafrost. But we can try to predict where and when it can happen to allow decision-makers and communities to protect people and resources. Reduction of global emissions may be the most reliable way to retard further release of carbon eternal permafrost into the atmosphere3, Let's keep the carbon where it belongs – safely frozen in a mind-blowing soils north.