EGU General Assembly 2020
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the Creative Commons Attribution 4.0 License.

Did the evolution of tropical river systems impact the Cenozoic climate system ? A preliminary study with the IPSL-CM5A2 earth system model.

Pierre Sepulchre and Julia Bres
Pierre Sepulchre and Julia Bres
  • Laboratoire des sciences du climat et de l'environnement, CNRS, CEA, UVSQ, Université Paris-Saclay, Gif-sur-Yvette, France (

Driven by plate tectonics and geodynamics, Earth surface has been reshaped during the Cenozoic, with the uplift of numerous mountain ranges. Climate modellers have been tackling the direct impact of these changes on climate for decades, essentially thanks to sensitivity experiments to topography, aiming at quantifying the impact of mountains on atmospheric and ocean dynamics. An indirect consequence of mountain uplift is changes in the continental river routing system, that can be relocated and provide the ocean with freshwater fluxes very different from the present. Here we focus on the Amazon and the Congo river, which routing are known to have been altered by the uplifts of the Andes and the East African Rift System, respectively. We carried out numerical simulations with the IPSL-CM5A2 earth system model in which we alternatively relocated or cut the runoff of these two rivers, and compared the results to simulations where topography only has been changed. We analyze the consequences of the changes in routing in terms of ITCZ position, precipitation spatial patterns, and salinity budgets and associated AMOC strength over the oceans. We show that depending on the region considered, the direct (mechanical) and indirect (hydrology) consequences of uplift on climate can either add up or counteract each other.


How to cite: Sepulchre, P. and Bres, J.: Did the evolution of tropical river systems impact the Cenozoic climate system ? A preliminary study with the IPSL-CM5A2 earth system model., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9387,, 2020

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Presentation version 1 – uploaded on 05 May 2020
  • CC1: Comment on EGU2020-9387, Julia Hargreaves, 06 May 2020

    I already asked 1 Q in chat, so I do the other here. You have a teaser at the end about the African humid period. Do you mean 6ka? What are you suggesting about this, that the additional river in N Africa may change SST which may influence monsoon?? Or land surface effects? Or...?

    • AC1: Reply to CC1, Pierre Sepulchre, 06 May 2020

      Thanks for your question Julia.
      Yes, I meant 6K, actually I was quite amazed by this paper on many aspects:
      1/ Indeed, if there was a massive river flowing at that latitude and time in the Atlantic, one wants to know how it impacted the salinity & SST fields, and in turns the rainfall regime. More generally, exploring how the latitude of river mouth impacts the ocean dynamics is quite facinating, I think.
      2/ It also involves massive rainfall over the region at that time, that GCMs often miss totally. So exploring this potential feedback is interesting.
      All the best,