Rock organic carbon oxidation CO release offsets silicate weathering sink.

Mountain uplift and erosion have regulated the balance of carbon between Earth's interior and atmosphere, where prior focus has been placed on the role of silicate mineral weathering in CO drawdown and its contribution to the stability of Earth's climate in a habitable state. However, weathering can also release CO as rock organic carbon (OC) is oxidized at the near surface; this important geological CO flux has remained poorly constrained. We use the trace element rhenium in combination with a spatial extrapolation model to quantify this flux across global river catchments.

High rates of rock organic carbon oxidation sustained as Andean sediment transits the Amazon foreland-floodplain.

The oxidation of organic carbon contained within sedimentary rocks ("petrogenic" carbon, or hereafter OC) emits nearly as much CO as is released by volcanism, thereby playing a key role in the long-term global C budget. High erosion rates in mountains have been shown to increase OC oxidation. However, these settings also export unweathered material that may continue to react in downstream floodplains.

Hydrological control of river and seawater lithium isotopes.

Seawater lithium isotopes (δLi) record changes over Earth history, including a ∼9‰ increase during the Cenozoic interpreted as reflecting either a change in continental silicate weathering rate or weathering feedback strength, associated with tectonic uplift. However, mechanisms controlling the dissolved δLi remain debated. Here we report time-series δLi measurements from Tibetan and Pamir rivers, and combine them with published seasonal data, covering small (<10  km) to large rivers (>10 km).

A lithium-isotope perspective on the evolution of carbon and silicon cycles.

The evolution of the global carbon and silicon cycles is thought to have contributed to the long-term stability of Earth's climate. Many questions remain, however, regarding the feedback mechanisms at play, and there are limited quantitative constraints on the sources and sinks of these elements in Earth's surface environments. Here we argue that the lithium-isotope record can be used to track the processes controlling the long-term carbon and silicon cycles.

Erosion of organic carbon in the Arctic as a geological carbon dioxide sink.

Soils of the northern high latitudes store carbon over millennial timescales (thousands of years) and contain approximately double the carbon stock of the atmosphere. Warming and associated permafrost thaw can expose soil organic carbon and result in mineralization and carbon dioxide (CO2) release. However, some of this soil organic carbon may be eroded and transferred to rivers.