Chemical weathering

What is our goal?

Chemical weathering is a fundamental process on the Earth’s surface as it regulates the flux of elements from continents to rivers. Weathering controls the formation of soils and the chemistry of rivers at human timescales and modulates the composition of the ocean, atmosphere, and biosphere over millions of years. In recent decades, global warming have changed the baseline conditions for weathering processes with broad consequences for river water quality, floodplain fertility, ocean composition, and biogeochemical cycle dynamics (Fig. 1).

My aim is to use and predict spatiotemporal isotope variations in river water to investigate weathering processes at different spatiotemporal scales.

How do we do this?

  1. We compile and analyze isotopes of river water or ancient river sediments using mass spectrometers.

  2. We use geostatistics and AI to tease out the controls of isotope variability and explain processes (e.g., Fig. 2) 

Why should you care?

Climate is rapidly changing weathering processes at the global scale but particularly in northern regions. Alpine glaciers retreat and permafrost thawing is changing the water-rock interactions in watersheds across the Arctic. Metal isotopes (e.g., lithium, strontium, potassium) are useful to understand these changing weathering processes in Arctic regions. As weathering is changing the chemistry of river is also evolving with implications for local ecosystems and human societies (Fig. 3).  

Isotopes are also useful when studying water-rock interactions at million years timescale. As climate and geology changed on the Earth' surface, river chemistry responded and influenced the composition of the atmosphere and of the ocean. These processes are key to understand the evolution of the Earth as an habitable planet and to better predict the evolution of the Earth's climate. For example, the composition of volcanic arcs have had a direct control on the chemistry of the ocean at million years timescales (Fig. 4). 

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Fig. 1 Chemical weathering over the Yukon River is rapidly changing with global warming.

Fig. 2 GIS process to investigate water chemistry through machine-learning regression

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Fig. 3 Lithium and strontium isotope variations across the Yukon River

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Fig. 4 Long-term variations of strontium isotopes in seawater compared to the strontium isotopes in volcanic arcs throughout the Phanerozoic (Bataille et al. 2017).