Arctic permafrost stores massive amounts of organic carbon in its frozen soils and deeper deposits. However, as the Arctic warms particularly rapidly, these deposits are thawing out. As a result, more and more greenhouse gases will be released into the atmosphere. There has been little research on where and how quickly permafrost thaws, as well as on the processes that cause the rapid thaw. PeTCaT (Rapid Permafrost Thaw Carbon Trajectories) is an international project that, above all, aims to increase our knowledge of these rapid thaw processes. Under the leadership of the Alfred Wegener Institute, researchers from Germany, the USA, Canada, the Netherlands, and Sweden plan to build a new dataset that will allow them to make projections about the possible developments and impacts of greenhouse gases from thawing permafrost. The project is funded by the non-profit organisation Schmidt Sciences.
“How quickly permafrost thaws depends on which region of the Arctic we are in and which processes are causing the thaw,” explains project leader Prof. Guido Grosse, Head of Permafrost Research Section at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). Although the active layer naturally thaws each summer, in a warming Arctic this seasonal thaw deepens over time, resulting in the permafrost gradually thawing from above by a few additional centimetres each year. This process is driven for example by continuously rising air temperatures, increased snow depths, or changes in vegetation that raise soil temperatures. However, we also see sudden thaw processes that can quickly cause several metres of permafrost to disappear per decade, or even per year – for example, when thawing coastlines suddenly break off, thermokarst lakes grow and deepen, or thaw slumps uncover icy subsoil. These rapid processes can release large amounts of previously permafrost-stored organic matter, which microorganisms can then convert into CO₂ and methane. “These abrupt processes are precisely where research is currently lacking and they are so far not considered in any climate model”, as Guido Grosse explains. “It is crucial to record these widespread rapid thaw processes and the effects they have so that we can understand their impact on the carbon cycle – particularly over the short time periods relevant for climate policy – in most cases years or a few decades at most.”
![[Translate to English:] Eiskeilpolygone und Thermokarstseen](/fileadmin/user_upload/AWI/Ueber_uns/Service/Presse/2025/4_Quartal/PM_PeTCaT/20230721_Eispolygone_Thermokarstseen_NWKanada_GuidoGrosse.jpg "Ice wedge polygons and thermokarst lakes")
This is precisely where PeTCaT enters the picture: the core question is what short-term impacts greenhouse gases suddenly released from degrading permafrost have on our climate – in addition to other natural and man-made emissions? And, in turn, what does that mean for the remaining carbon budget available to reach specific climate goals and our climate policies? Over the next five years, the project team will develop a range of climate projections to show how the carbon cycle in the Arctic permafrost region and its influence on global climate could develop in the future. The projections will also show how these additional emissions could trigger interactions with altered vegetation patterns and biogeochemical processes under various climate scenarios.
In order to achieve this, the research team is building several new datasets: on the one hand, they are using remote sensing and deep learning methods to map abrupt thaw processes across the Arctic. From this, they hope to map where, how frequent, and how intensely these processes occur, as well as how they relate to climate patterns and extreme events. They will combine this information with new comprehensive datasets on ground ice and soil carbon as well as process models, in order to show how such changes could develop in future. On the other hand, the team is also collecting data in the Arctic: at selected locations, they are investigating how different types of organic matter decompose following permafrost thaw. To accomplish this, researchers will collect soil samples, measure the production and release of greenhouse gases on site, conduct laboratory experiments, and combine these new measurements and observations with existing datasets covering the whole of the Arctic. “Within the PeTCaT project at AWI, we are investigating changes in thermokarst lakes, carbon storage in the soil and soil biogeochemistry, as well as how intensely the permafrost is warming,” explains Guido Grosse.
Researchers from six institutions are collaborating on the PeTCaT project: the Alfred Wegener Institute (Germany), the University of Alaska Fairbanks (USA), the University of Alberta (Canada), the University of Hamburg (Germany), Stockholm University (Sweden) and Vrije Universiteit Amsterdam (Netherlands). They bring together expertise in permafrost research, soil carbon and biogeochemistry of greenhouse gases, remote sensing, process modelling, and global climate modelling. “We need to better understand the processes and interactions behind abrupt permafrost thaw”, summarises Guido Grosse. “Our current level of knowledge does not allow us to reliably assess the impact of these suddenly released greenhouse gases on the atmosphere and the climate. They could reduce the carbon budget that remains available to humanity to reach the 1.5-degree target, thereby also reducing our scope to manoeuvre when it comes to drastically curbing man-made emissions.”
About PeTCaT (Rapid Permafrost Thaw Carbon Trajectories)
Project duration: Five years, from October 2025 to September 2030
Funding amount: 10.4 million US dollars from Schmidt Sciences
Geographical focus: the entire Arctic, with field studies in Alaska, Canada and Finland
Website: www.schmidtsciences.org/vicc/
About Schmidt Sciences
Schmidt Sciences is a non-profit organisation that funds research projects in the fields of AI and advanced computing, astrophysics, life sciences, climate and space, with the aim of enabling high-impact and top-quality science. Through its VICC (Virtual Institute for the Carbon Cycle) research initiative, Schmidt Sciences provides targeted support for research into better understanding the carbon cycle and assessing how it may develop in future. PeTCaT is one of four VICC-funded projects.
![[Translate to English:] Tauender Permafrost mit "Slumps"](/fileadmin/_processed_/7/1/csm_20250718_Permafrost_Kueste_Alaska_GuidoGrosse_2a133d39e3.jpg "Retrogressive thaw slump")
![[Translate to English:] Eiskeilpolygone und Thermokarstseen](/fileadmin/_processed_/f/6/csm_20230721_Eispolygone_Thermokarstseen_NWKanada_GuidoGrosse_8006a2a5e3.jpg "Ice wedge polygons and thermokarst lakes")
![[Translate to English:] Tauender Permafrost mit "Slump"](/fileadmin/_processed_/0/2/csm_20230715_TauenderPermaforstNWKanada_GuidoGrosse_2d5e2da7b1.jpg "Retrogressive thaw slump")