Biological and geological carbon cycles are closely linked, according to a study published in Nature. Results from investigations in rivers on the Qinghai–Tibet Plateau challenge the simplified view of thawing permafrost as solely a carbon source.
Photo Credit: Liwei Zhang
Scientific Frontline: Extended "At a Glance" Summary: Riverine Carbon Sinks in Thawing Permafrost
The Core Concept: As permafrost degrades due to climate warming, intensified chemical rock weathering in river catchments creates a geological carbon sink that can significantly offset the biological release of carbon dioxide.
Key Distinction/Mechanism: Thawing permafrost is conventionally modeled solely as a carbon source due to the microbial breakdown of ancient organic matter. However, permafrost degradation also exposes reactive minerals to water; this accelerates chemical weathering processes that consume atmospheric carbon dioxide and convert it into dissolved inorganic forms, shifting the net carbon balance.
Major Frameworks/Components:
- Biogeochemical Coupling: The concurrent and closely linked operations of microbial carbon cycling (emission) and geological rock weathering (uptake).
- Isotopic and Geochemical Modeling: The utilization of isotopic tracers and dissolved carbon measurements to quantify mass transfers into inorganic carbon states.
- Cryosphere Dynamics: The correlation between varying permafrost continuity (from continuous to isolated) and corresponding rates of chemical weathering and carbon absorption.
Branch of Science: Biogeochemistry, Climatology, Geomorphology, Hydrology.
Future Application: Integration into global climate and carbon-cycle models to refine predictive assessments of how permafrost degradation influences long-term warming trajectories and greenhouse gas budgets.
Why It Matters: The research challenges the prevailing scientific assumption that permafrost degradation functions exclusively as a positive climate feedback loop, revealing that geological weathering can offset biological carbon dioxide emissions by an average of 35 percent—and occasionally over 100 percent in highly fragmented permafrost zones.
A new study published in Nature shows that rock weathering increasingly counteracts river \(CO_2\) emissions as permafrost degrades. A collaborative team of researchers from Umeå University in Sweden and East China Normal University conducted the study.
Thawing permafrost is often viewed as a growing source of greenhouse gases, as climate warming releases ancient carbon stored in frozen soils. However, the study reveals a more complex picture. As permafrost thaws, rivers may also develop an overlooked capacity to remove carbon dioxide (\(CO_2\)) through intensified rock weathering. Researchers found that warming and permafrost degradation expose reactive minerals and increase water–rock interactions, accelerating chemical weathering processes that consume \(CO_2\). In some river catchments, this geological carbon uptake partially or even fully offsets river \(CO_2\) emissions.
The international research team investigated 50 rivers across the Qinghai–Tibet Plateau, Earth’s largest high-altitude cryosphere outside the polar regions, to understand how thawing permafrost reshapes carbon cycling. By combining measurements of river \(CO_2\) emissions, dissolved carbon, isotopic tracers, and geochemical modeling, the researchers found evidence that thawing landscapes intensify chemical weathering, transferring carbon into dissolved inorganic forms while consuming atmospheric \(CO_2\).
Carbon Uptake Can Even Exceed Emissions
“We found that river \(CO_2\) emissions decline while carbon uptake through rock weathering increases as permafrost cover decreases,” said Liwei Zhang, a biogeochemist at East China Normal University. “In some catchments where permafrost has become patchier, weathering-driven carbon uptake was large enough to offset or even exceed river \(CO_2\) emissions.”
"Our Findings Show That Biological and Geological Carbon Cycles Are Tightly Linked"
Across the study region, the team estimated that carbon uptake from rock weathering offsets roughly 35 percent of river \(CO_2\) emissions on average. In regions with continuous permafrost, the offset was relatively small. However, in landscapes with discontinuous or isolated permafrost, weathering-driven carbon uptake sometimes exceeded 100 percent of river \(CO_2\) emissions, suggesting that geological carbon uptake can rival biological carbon release.
Biological and Geological Carbon Cycles Linked
The findings challenge a simplified view of thawing permafrost as solely a carbon source. As frozen soils thaw, rivers receive large inputs of ancient organic carbon that microbes convert into greenhouse gases released into the atmosphere. The new study suggests that geological processes operating alongside biological ones may partly counterbalance these emissions.
Still, the researchers caution that rock weathering is not a simple or permanent climate solution. Carbon cycling in thawing landscapes remains complex, and some weathering reactions can also release \(CO_2\), depending on mineral composition. The study instead highlights a mechanism that remains poorly represented in many climate and carbon-cycle models.
“Our findings show that biological and geological carbon cycles are tightly linked,” said Jan Karlsson, a professor in the Department of Ecology, Environment, and Geosciences at Umeå University. “To understand whether thawing permafrost ultimately amplifies or dampens climate warming, we need to consider both the carbon released from ancient soils and the carbon consumed through rock weathering.”
The researchers argue that future climate assessments should move beyond a sole focus on biologically driven carbon emissions and incorporate geological carbon sources and sinks that emerge as frozen landscapes thaw.
Published in journal: Nature
Title: Rock weathering can counteract river \(CO_2\) emissions induced by permafrost thaw
Authors: Liwei Zhang, Aaron Bufe, Joshua F. Dean, Gerard Rocher-Ros, Ryan A. Sponseller, Emily H. Stanley, Jan Karlsson, David E. Butman, Ran Liu, Lijun Hou, Jinzhi Ding , Shilong Piao, Xinghui Xia, and Tom J. Battin
Source/Credit: Umeå University | Anna-Lena Lindskog
Edited by: Scientific Frontline
Reference Number: es061726_02
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