All posts by aaronbufe@gmail.com

New Paper: Riverine carbon fluxes across the Tibetan Plateau

New Paper

We measured carbon emissions and water chemistry in 50 headwater rivers draining 780,000 km2 of the Tibetan Plateau.

The rivers flow in landscapes underlain by continuous permafrost and landscapes in which the permafrost has retreated since the last glacial maximum. They collect organic carbon from soils and dissolved inorganic carbon that is fixed by rock-weathering.

Where the permafrost cover is continuous, rivers emit CO2 from degrading (permafrost) soil carbon. Weathering reactions in these catchments are relatively slow.

In landscapes with (almost) no permafrost, carbon fluxes from weathering are faster than CO2 emissions from rivers.

Thus, as permafrost landscapes transition to landscapes without permafrost cover, chemical weathering reactions may play an ever more important role in riverine carbon cycling.

Interestingly, weathering can affect the carbon cycle in different ways. Where sulfide minerals are present, weathering reactions can emit CO2. Where silicate minerals dominate, weathering draws down CO2 from the atmosphere.

About: Zhang, L.§, Bufe, A. §, Dean, J.F., Rocher-Ros, G., Sponseller, R.A., Stanley, E.H., Karlsson, J., Butman, D.E., Liu, R., Hou, L., Ding, J., Piao, S., Xia, X., Battin, T.J. (2026). Rock weathering can counteract river CO2 emissions induced by permafrost thaw. Nature. Journal Link
§ L.Z. and A.B. contributed equally to this work.

New Paper: Soil development in alpine glacier forelands

New Paper

The paper summarizes a four-year effort of 4 PhD students, 4 MSc students and many helping hands within the SNF/DFG-funded Hillscape project.

We measured 39 different physical, biological, and chemical soil-properties on glacial moraines that are 30 – 13,000 years.

Many of the measured characteristics show very similar changes through time. This observation led us to define a “Hillslope development Index” (HDI) that summarizes the overall state of physical and biological development of the hillslopes, and we find that the HDI saturates around 5000 – 10,000 years in both glacier forefields.

About: Greinwald, K., Bufe, A., Blume, T., Demand, D., Egli, M., Gebauer, T., Hartmann, A., Maier, F., van Meerveld, I., Musso, A., Scherer-Lorenzen, M., Weiler, M. (2026). Co-development of physical and biological variables on glacial hillslopes over millennia. Earth and Planetary Science Letters, 688, 120100. Journal Link

New paper: Climate warming and weathering

New Paper

Sen Xu analyzed the changes in weathering fluxes from the headwaters of the Yangtze River over a period of seven years. During this time, climate warmed substantially, and Sen’s data show a substantial increases in solute fluxes from evaporite weathering (especially in the permafrost-rich headwaters of the JSR river). These changes could enhance secondary carbonate precipitation and lead to CO2 release. In addition, sulfide weathering becomes relatively more important than silicate and carbonate weathering reactions. This finding implies that warming and hydrological changes lead to a shift toward less CO2 drawdown and more CO2 release from rock weathering.

About: Xu, S., Bufe, A., Kemeny, P.C., Klaus, M., Zhong, J., Ma, T., Li, D., Li S.L., (2025). Climate warming and strengthened hydrologic cycle accelerate CO2 release from rock weathering. Geochimica et Cosmochimica Acta, 407, 174-192. Journal Link

New paper: CO2 outgassing from floodplains

New Paper

A new paper on the fluxes and sources of CO2 outgassing from different floodplain deposits is out now. Sophia measured CO2 that is emitted from river channels, riverbank sediments and older floodplain deposits along the Rio Bermejo in Argentina. She found the highest fluxes occur away from the modern channel and riverbanks. Here, emissions are highly seasonal (highest fluxes during the wet season) and are influenced by the respiration of recent and old organic matter.

Based on her measurements, Sophie estimated that sediments and soils in the Rio Bermejo floodplains emit almost 450 tons of carbon per square kilometer and per year.

About: Dosch, S., Hovius, N., Bufe, A., Repasch, M., Scheingross, J., Vieth-Hillebrand, A., Sachse, D. (2025). CO2 Fluxes Driven by Floodplain Morphology and Seasonality at the Rio Bermejo, Argentina. Journal of Geophysical Research: Biogeosciences, 130(8), e2024JG008517. Journal Link

New paper: Evolution of channel belts

Publication

About: Turowski et al., (2025), Earth Surface Dynamics (link)

Chapter four of our work on how channel belts and valleys set their widths is out now. We use a random walk model to make predictions on how channel belts widen. The model is consistent with observations from both experiments and the field, and it is governed by three timescales.

On short timescales, the river moves in just one direction. Then, the channel belt widens linearly at a rate that depends on the rivers “lateral transport capacity”. We introduced the concept of this lateral transport capacity here. On medium timescales, the river moves back and forth across the channel belt. Then, the evolution of channel-belt width can be modelled with an exponential approach to an asymptote. On long timescales the river erodes the margins of the active channel belt only occasionally. The channel belt widens as the squareroot of time.

Evolution of channel-belt width over time. Colored lines are data from a random walk model. Dotted, dash-dotted and dashed lines are predictions from analytical solutions for the linear-, exponential-, and squareroot-widening phases.

The model makes predictions on the age of floodplain surfaces, and it fits rare data on floodplain ages well.

The distribution of floodplain ages in the field scale with a power-law exponent of ~3/2 as predicted by the random walk model.

ERC Starting Grant

Funding

I am thrilled to announce that I received funding from the European Research Council (ERC) to study weathering of sediments on floodplains. With this project, I hope to better understand how sediment transport from mountains across lowlands impacts Earth’s carbon cycle. Two PhD positions will likely be advertised throughout next year. Stay tuned for more updates.