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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2020-4
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2020-4
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 20 Jan 2020

Submitted as: research article | 20 Jan 2020

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This preprint is currently under review for the journal BG.

Physical and biogeochemical impacts of RCP8.5 scenario in the Peru upwelling system

Vincent Echevin1, Manon Gévaudan1,2,3, Dante Espinoza-Morriberon2, Jorge Tam2, Olivier Aumont1, Dimitri Gutierrez2,4, and François Colas1,2 Vincent Echevin et al.
  • 1Sorbonne Université, LOCEAN-IPSL, CNRS/IRD/MNHN, 4 place Jussieu, 75252 Paris, France
  • 2Instituto del Mar del Peru (IMARPE), Esquina General Gamarra y Valle, Callao, Perú
  • 3Laboratoire d'Etudes en Géophysique et Océanographie Spatiales, 14 av. E.Belin, 31400 Toulouse, France
  • 4Laboratorio de Ciencias del Mar, Universidad Peruana Cayetano Heredia, Lima, Perú

Abstract. The northern Humboldt current system (NHCS or Peru upwelling system) sustains the world's largest small pelagic fishery. While a nearshore surface cooling has been observed off southern Peru in recent decades, there is still considerable debate on the impact of climate change on the regional ecosystem. This calls for more accurate regional climate projections of the 21st century, using adapted tools such as regional eddy-resolving coupled biophysical models. In this study 3 coarse-grid Earth System Models (ESMs) from the Coupled Model Intercomparison Project (CMIP5) are selected based on their biogeochemical biases upstream of the NHCS and simulations for the so-called business-as-usual RCP8.5 climate scenario are dynamically downscaled at 10 km resolution in the NHCS. The impact of regional climate change on temperature, coastal upwelling, nutrient content, deoxygenation and the planktonic ecosystem is documented. We find that the downscaling approach allows to correct major physical and biogeochemical biases of the ESMs. All regional simulations display a surface warming regardless of the coastal upwelling trends. Contrasted evolutions of the NHCS oxygen minimum zone and enhanced stratification of phytoplankton are found in the coastal region. Whereas trends of downscaled physical parameters are consistent with ESM trends, downscaled biogeochemical trends differ markedly. These results suggest that more realism of the ESMs is needed in the eastern equatorial Pacific to gain robustness in the projection of regional trends in the NHCS.

Vincent Echevin et al.

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Vincent Echevin et al.

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Short summary
The coasts of Peru encompass the richest fisheries in the entire ocean. Therefore it is very important for this country to understand and possibly project how the nearshore marine ecosystem will evolve under climate change. Numerical models are very useful because they can represent precisely the evolution of key parameters such as temperature, water oxygenation and plankton biomass. Here we study the evolution of the marine ecosystem in the 21st century under 3 possible climate scenarios.
The coasts of Peru encompass the richest fisheries in the entire ocean. Therefore it is very...
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