A vast frozen carbon vault
The West Siberian Lowlands contain the world's largest high-latitude wetland, an area of over 900,000 square kilometers almost entirely covered by peatlands. For millennia, this region is a large carbon storage unit. The peat, composed of partially decayed vegetation like Sphagnum moss, has accumulated since the end of the last glacial period, with a rapid phase of growth starting around 11,000 years ago. This organic matter is locked within permafrost, soil that has remained frozen for at least two consecutive years.
This immense frozen landscape holds a large portion of the planet's soil carbon. Estimates suggest the northern hemisphere's frozen soils contain about 1,700 billion tonnes of carbon. The West Siberian peatlands alone may store over 53.8 billion metric tons of carbon. The waterlogged and frozen conditions prevent the complete decomposition of dead plant material—primarily Sphagnum mosses, which can hold 16 to 26 times their dry weight in water. This process has created peat layers with a mean depth of 2.56 meters, though some deposits reach 10 meters thick.
The thaw and the feedback loop
Global warming is occurring three to four times faster in the Arctic than the global average. This accelerated warming is thawing the permafrost that has kept the Siberian peat stable for thousands of years. As the ice-rich ground melts, the previously frozen organic matter becomes available to microbes. Under waterlogged, anaerobic conditions, these microbes break down the carbon and release methane (CH4).
Methane is a greenhouse gas. Over a 20-year period, it is more than 80 times as powerful at trapping heat than carbon dioxide (CO2). The release of this gas from thawing permafrost creates a positive feedback loop: the released methane contributes to more warming, which in turn thaws more permafrost, releasing even more methane. The 2020 Siberian heatwave, which saw temperatures peak at 6°C above normal, led to a detectable increase in atmospheric methane concentrations over the Taymyr Peninsula.
The physical landscape is also changing. As ground ice melts, the land surface subsides, creating irregular terrain of marshy hollows known as thermokarst. These depressions often fill with water, forming thousands of new shallow lakes, many a kilometer across. These thermokarst lakes become sites for methane production and release, further accelerating the feedback cycle.