Investigating climate controls on weathering processes in modern and ancient river systems

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The overarching goal of this research program is to better understand and predict the controls of chemical weathering at different spatiotemporal scales.***Chemical weathering reactions transfer elements from the continental crust to rivers and to the ocean. This process is key to explaining why the earth is habitable by regulating biogeochemical cycles. For example, when the climate warms, the rate of chemical weathering increases, thereby accelerating the rate of marine carbonate precipitation. Carbonate precipitation consumes atmospheric carbon dioxide (CO2) and cools the climate, ultimately lowering chemical weathering rates. This climate-weathering feedback has allowed the Earth to maintain an active water cycle by keeping temperature within a tight and favorable range. Chemical weathering is also an important process at human timescales. For example, chemical weathering influences soil proprieties (e.g., fertility) and the chemistry of rivers, thereby controlling the sustainability of ecosystems and human societies. Global warming is rapidly changing the background conditions for chemical weathering reactions. Novel studies are urgently needed to investigate the interactions of climate and weathering to better reconstruct the past and forecast the future conditions on the Earth's surface. However, studying weathering is challenging because many geo-environmental variables influence this process. In the next 5 years, my group will work towards my overarching goal by studying the response of weathering to warming at different spatiotemporal scales as defined by the three following short-term goals. Our first goal will investigate how changes in permafrost cover influence weathering across the Yukon River catchment. Our second goal will develop novel paleo-weathering proxies to assess how soils of Laramide floodplains responded to early Paleogene warming trends and events. Our third goal will refine the marine strontium isotope budget at present-day to investigate the changes in weathering between glacial and interglacial periods. The results from this work will have regional implications for policy makers, helping them to improve the sustainability of specific environments (e.g., Yukon River catchment). This program will also advance our knowledge on the role of weathering as a long-term driver of climate, ocean composition and biosphere evolution. This knowledge is crucial to develop more robust Earth system models to reconstruct the past and predict the future of Earth's biogeochemical evolution. This research program will use field and laboratory experience, team work and collaborative multi-disciplinary projects to train 7 BSc, 2 MSc and 3 PhD. Through this training, HQP will improve their soft skills while gaining strong technical knowledge in isotope geochemistry and numerical methods. This program will educate versatile environmental geoscientists capable of managing natural resources in Canada and beyond. *****