A new study in Nature reveals that thawing permafrost on the Qinghai-Tibet Plateau may trigger a natural geological process that partly offsets carbon emissions from regional rivers.
Study Methodology
Researchers from Umeå University in Sweden and East China Normal University conducted the study. The team analyzed 50 rivers across the Qinghai-Tibet Plateau, measuring CO₂ emissions, dissolved carbon, isotopic tracers, and utilizing geochemical models.
Key Findings
- As permafrost thaws, previously buried minerals become exposed and water interacts more extensively with rock surfaces. This accelerates chemical weathering, a process that consumes atmospheric CO₂.
- In some river catchments where permafrost is discontinuous or isolated, the carbon uptake from weathering was large enough to offset or exceed CO₂ emissions from the rivers.
- Across the entire study area, rock weathering offset approximately 35 percent of river CO₂ emissions on average.
- In certain areas, weathering-driven carbon uptake exceeded 100 percent of river CO₂ emissions, meaning more CO₂ was removed by weathering than was emitted by the rivers.
"In some river catchments where permafrost is discontinuous or isolated, the carbon uptake from weathering was large enough to offset or exceed CO₂ emissions from the rivers."
Background and Complexity
As permafrost thaws, microbes break down ancient organic matter, releasing greenhouse gases. However, this study highlights that geological processes, specifically the chemical weathering of exposed minerals, also occur concurrently. The researchers noted that depending on the minerals involved, some weathering reactions can release CO₂ rather than consume it.
Researcher Statements
- Liwei Zhang (biogeochemist at East China Normal University) stated that river CO₂ emissions decline while carbon uptake through rock weathering increases as permafrost cover decreases.
- Jan Karlsson (professor at Umeå University) stated that biological and geological carbon cycles are tightly linked. He added that to understand whether thawing permafrost ultimately amplifies or dampens climate warming, both the carbon released from ancient soils and the carbon consumed through rock weathering must be considered.
"Both the carbon released from ancient soils and the carbon consumed through rock weathering must be considered."
Implications
The researchers emphasized that rock weathering should not be viewed as a simple or permanent solution to climate change, as carbon cycling in thawing environments is complex. The study suggests that future climate assessments should account for geological sources and sinks (including rock weathering) as frozen landscapes continue to thaw. This mechanism is not fully represented in many current climate and carbon cycle models.