Cenozoic cooling and weathering
Over the past 50 million years, atmospheric CO2 levels have dropped and the Earth has cooled. Though this long-term cooling has fundamentally transformed the Earth and set the stage for the evolution of humans, we still debate why CO2 has declined and why the Earth has cooled. Our work focuses on understanding how weathering--which removes CO2 from the atmosphere and transfers it to the oceans, where it is buried as carbonate rock--may have both driven and reacted to this cooling. We have found that, to drive such cooling, the reactivity of the Earth's surface must have increased, such that the global weathering zone is able to produce the same alkalinity flux in cool, low-CO2 climates as during warm, hothouse climates. The idea that the silicate weathering feedback may not be static, but, rather, may dynamically change and drive climatic change itself, has led to a broad-scale re-evaluation of past episodes of climate change and an examination as to whether changes in the silicate weathering feedback may be implicated.
A schematic of how land-surface reactivity may change due to changes in erosion and climate. Based upon work presented in Rugenstein et al. (2019). Graphic developed by GFZ Potsdam.
Relevant Publications:
Jeremy K. Caves Rugenstein, Daniel E. Ibarra, Shuang Zhang, Noah J. Planavsky, & Friedhelm von Blanckenburg. Isotope mass-balance constraints preclude that mafic weathering drove Neogene cooling. Proceedings of the National Academy of Sciences. v. 118 (30): e2026345118. 10.1073/pnas.2026345118.
This letter is a comment on Emergence of the Southeast Asian islands as a driver for Neogene cooling by Park et al. (published in 2020). There is a corresponding reply by Park et al., available here.
Erica D. Erlanger, Jeremy K. C. Rugenstein, Aaron Bufe, Vincenzo Picotti, & Sean Willett. Controls on Physical and Chemical Denudation in a Mixed Carbonate‐Siliciclastic Orogen. Journal of Geophysical Research--Earth Surface. v. 126: e2021JF006064. 10.1029/2021jf006064.
See a nice summary of this paper by co-author Aaron Bufe here.
Aaron Bufe, Niels Hovius, Robert Emberson, Jeremy K. C. Rugenstein, Albert Galy, Hima J. Hassenruck-Gudipati, & Jui-Ming Chang. Co-variation of silicate, carbonate and sulfide weathering drives CO2 release with erosion. Nature Geoscience. v. 14: 211-216. 10.1038/s41561-021-00714-3.
Donald Penman, Jeremy K. Caves Rugenstein, Daniel E. Ibarra, & Matthew J. Winnick. Silicate weathering as a feedback and forcing in Earth's climate and carbon cycle. Earth Science Reviews. v. 209: 103298. 10.1016/j.earscirev.2020.103298.
Jeremy K. Caves Rugenstein.What goes down must come up. Nature Geoscience. v. 13: 5-7. 10.1038/s41561-019-0514-4.
Jeremy K. Caves Rugenstein, Daniel E. Ibarra, & Friedhelm von Blanckenburg. Neogene cooling driven by land surface reactivity rather than increased weathering fluxes. Nature. v. 571: 99-102. 10.1038/s41586-019-1332-y.
Richard F. Ott, Sean F. Gallen, Jeremy K. Caves Rugenstein, Susan Ivy‐Ochs, David Helman, Charalampos Fassoulas, Christof Vockenhuber, Marcus Christl, & Sean D. Willett. Chemical Versus Mechanical Denudation in Meta‐Clastic and Carbonate Bedrock Catchments on Crete, Greece, and Mechanisms for Steep and High Carbonate Topography. Journal of Geophysical Research: Earth Surface. v. 124. 10.1029/2019JF005142.
Daniel E. Ibarra, Jeremy K. Caves Rugenstein, Aviv Bachan, Andres Baresch, Kimberly V. Lau, Dana L. Thomas, Jung-Eun Lee, C. Kevin Boyce, & C. Page Chamberlain. Modeling the evolution of land plants and the silicate weathering feedback. American Journal of Science v. 319 (1): 1-43. 10.2475/01.2019.01. pdf.
Cin-Ty A. Lee, Jeremy K. Caves, Hehe Jiang, Wenrong Cao, Adrian Lenardic, N. Ryan McKenzie, Oliver Shorttle, Qing-zhu Yin, and Blake Dyer. Deep mantle roots and continental emergence: implications for whole-Earth elemental cycling, long-term climate, and the Cambrian explosion. International Geology Review. v. 60 (4): 431-448 10.1080/00206814.2017.1340853. pdf.
Daniel E. Ibarra, Seulgi Moon, Jeremy K. Caves, C. Page Chamberlain, and Kate Maher. Concentration-discharge patterns of weathering products from global rivers. Acta Geochimica. v. 36 (3): 405-409. 10.1007/s11631-017-0177-z. pdf.
Jeremy K. Caves, Adam B. Jost, Kimberly V. Lau, and Kate Maher. Cenozoic carbon cycle imbalances and a variable silicate weathering feedback. Earth and Planetary Science Letters; vol. 450: 152-163. 10.1016/j.epsl.2016.06.035. pdf.
Daniel E. Ibarra, Jeremy K. Caves, Seulgi Moon, Dana L. Thomas, Jens Hartmann, C. Page Chamberlain, and Kate Maher. Differential weathering of basaltic and granitic catchments from concentration–discharge relationships. Geochimica et Cosmochimica Acta; vol. 190: 265-293. 10.1016/j.gca.2016.07.006. pdf.