17% of the Earths land surface area is underlain by permafrost. Permafrost regions cover ¼ of the land area within the Northern Hemisphere including large parts of Russia, Canada, Alaska, as well adfs the high mountain regions such as the European Alps and Tibet. Permafrost areas, particularly those within the Arctic, are symbiotic with the people that live there with an estimated four million people currently living on top of Arctic permafrost. Indigenous nomadic tribes have historically exploited permafrost as a cold storage unit for the long term preservation of food and drink. Infrastructural developments often take place on top and within permafrost exploiting its rigidity. These include streets, oil-, water- and sewage pipelines, airports, but also vast swathes of housing and industry. Permafrost thawing would result in irreversible damage to infrastructure and facilities constructed upon it.
Besides its local and certainly costly impacts on arctic communities, permafrost thawing could potentially have a disastrous impact on the global climate since permafrost reacts quickly to changes in air temperature. Even what most people consider small increases in air temperature over a longer period of time can warm up and eventually lead to thawing and loss of permafrost. The potential impacts on the global climate system are that alarming because of the so-called “permafrost carbon feedback”.
Permafrost soils are a vast source of organic carbon containing an estimated 1400 gigatons of frozen carbon in the form of buried plant and animal remains. Dr. Biskaborn (AWI) explains what would happen if this frozen carbon begins to warm “When the permafrost soil warms above 0°C and begins to thaw, bacteria start to break down organic material such as plant and animal remains locked in permafrost. This leads to the release of carbon dioxide and methane gases which subsequently enter the atmosphere, drastically increasing the greenhouse effect for the entire global climate system”. Some studies estimate that this process could lead to a 0.13 to 0.27°C temperature increase by 2100.
In order to deepen our knowledge about permafrost thawing and its global impact, an international team of scientists lead by Dr. Boris Biskaborn from the Alfred Wegener Institute Helmholtz centre for Polar and Marine research (AWI), Potsdam conducted long-term permafrost research worldwide. The study used permafrost temperatures measured in boreholes included within the Global Terrestrial Network for Permafrost (GTN-P). The scientists involved in the project continuously measured permafrost temperatures in 154 permafrost boreholes distributed globally over a long time period (2007 to 2016). In order to remove the effect of seasons on permafrost temperature, borehole temperatures were measured at 10m depths below the ground surface. Boreholes are key to track fluctuations in permafrost temperatures “Boreholes are vertical holes drilled in the Earth´s surface that can be used to study a whole variety of Earth processes. For example boreholes can be lined and used for permafrost temperature measurement or other observations of rock and sediment physics” explains Stuart Vyse a PhD student of Dr. Biskaborn.
The results of the study are alarming. It showed that permafrost, which is ground at or below 0°C for at least a two year period, is warming rapidly at a global scale. Of all of the boreholes measured and included within the study, 71 recorded dramatic permafrost warming, with 5 already showing permafrost thawing with measured temperatures above 0°C. Twelve boreholes were seen to cool, whilst the rest remained unchanged. Two boreholes at sites in northern Siberia (Samoylov Island and Marre Sale) showed an exceptional rise in permafrost temperature. In both of them a 1°C temperature increase was observed since 2008.
The largest rise in permafrost temperature was seen in the region of almost complete permafrost cover (90-100%), the so-named “Arctic continuous permafrost zone”. The study showed that temperatures there increased by an average of 0.39°C from 2007 to 2016. In comparison, the more southerly discontinuous permafrost zone consisting of less than 90% permafrost coverage, suffered a smaller but none-the-less significant 0.20°C temperature rise over the same time frame. Why is permafrost warming between these two zones different? Dr. Biskaborn explains that his team of scientists found multiple corresponding effects to explain this difference. The most important signal came from comparing air temperature and snow thickness data with the temperature changes observed within permafrost. Air temperature increase could explain the strong warming of the northern continuous permafrost. In the more southerly zone of discontinuous permafrost increases in snow depth as well as the shift of the onset of snow to earlier months of the year could play a large role in controlling permafrost temperature. However, the so-termed “latent heat effect” is also contributing to the fact that simply cold permafrost is warming more rapidly than permafrost that has already warmed. When the permafrost temperature gets close to zero and parts of the ice are melting, the energy is firstly absorbed by the phase change from ice to water. This process is causing a zero curtain effect best visible in seasonal time series data. Studies using satellite images of widely distributed thermokarst lakes within arctic permafrost areas have shown that these water bodies are also expanding rapidly, a sure sign of increasing permafrost thaw on a large scale.
Permafrost warming was however by no means limited solely to the arctic. Permafrost in boreholes in the global high mountain regions of Europe, Nordic and Central Asia warmed up by 0.19°C. One borehole in the Aldan mountains of Yakutia, Siberia witnessed an astonishing 1.15°C temperature rise at 25m depth. “High mountain regions containing permafrost such as in Asia or Europe play a huge role in supplying water to some of the world’s biggest economies” explains Stuart Vyse “China for example depends strongly on rivers that receive the majority of their water from high altitude permafrost regions in Tibet. It is hard to know exactly how rising permafrost temperatures and thaw would affect the water balance and hence water supply to these countries in the future”.
The direct impact that permafrost thawing will have on the livelihood of the 4 million people that live within the Arctic cannot be overstated. Over wide areas of Siberian Russia the increase in summer active layer thickness resulting from permafrost warming is already leading to building subsidence and damage on a large scale. Buildings within industrial cities such as Bilibino in northeast Siberia can be seen in places to be slowly consumed by expanding wetland areas. Two Russian students who took part on the AWI Chukotka 2018 expedition highlighted the need for better understanding of permafrost thawing: “Our towns and villages are living with the ever increasing threat of at any time sinking into the ground. The future of our communities looks bleak if we do not address permafrost warming and thaw”.
If permafrost continues to warm and thaw as this study shows, many communities across the arctic will be threatened and may be eventually forced to migrate due to uninhabitable conditions. This will put pressure on other regions that will already be feeling the effect of increased carbon input to the atmosphere from permafrost release through global warming.
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