As the climate warms, thawing permafrost exposes long-frozen organic carbon that escapes as carbon dioxide from soils and rivers, feeding back into further warming. A study in Nature, co-led by LMU sedimentology professor Aaron Bufe and biogeochemist Liwei Zhang of East China Normal University, asks whether rock weathering, a process rarely considered in permafrost research, can claw some of that carbon back.
The team combined CO2 emission measurements with chemical analyses from 50 rivers feeding Asia's largest river systems on the Qinghai-Tibet Plateau, the largest continuous permafrost landscape outside the polar regions. The study area spans about 780,000 square kilometres and elevations from 1,650 to 4,820 metres, covering ground where permafrost is continuous, sporadic or already gone.
Across the region, weathering offsets about 35 per cent of river CO2 emissions. In continuous permafrost the figure is only around 15 per cent, but where permafrost is sporadic the offset can exceed 100 per cent, meaning weathering may matter more as frozen ground declines. The effect depends on mineral type: silicate weathering absorbs carbon, while sulphide weathering can release it.
The authors stress that weathering is no licence for complacency. Annual human emissions are roughly 100 times greater than the carbon this mechanism sequesters, so cutting emissions remains decisive. The contribution is rather to show that permafrost thaw's net climate effect is more complex than assumed, and that organic and inorganic carbon cycles must be modelled together.