Séminaire ISTerre

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A 6-year cycle in the Earth System

jeudi 4 avril 2024 - 15h00

Julia Pfeffer - Magellium, Toulouse
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A 6-year cycle has been detected in many variables of the Earth's system, revealing dynamical processes in the Earth's core, mantle, and superficial fluid envelopes. A 6-year cycle has long been observed in the length of day and robustly attributed to dynamical processes in the fluid outer core, which is supported by satellite and in situ observations of the geomagnetic field and subsequent core flow models. A 6-year cycle is also evidenced in the atmospheric angular momentum, which is found to be in phase opposition with the length of day. Because the length of day is opposed in sign with the Earth’s rotation rate, this means that the atmosphere rotates together with the solid Earth at 6 years. We suggest here that dynamical processes occurring in the Earth’s core drive a 6-year oscillation in the rotation of the mantle and atmosphere, inducing changes in the climate system at similar periodicities. Oscillations at a typical period of 6 years are indeed observed in the zonal winds, atmospheric water cycle, global mean surface temperature, global mean sea level, and terrestrial water storage changes. Such observations raise new questions about the relationships between internal and external geodynamics. Further studies are needed in particular to better understand the nature of the coupling mechanisms linking changes in the rotation of the solid Earth and the atmosphere, hence inferred changes in the atmospheric circulation and climate.

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Equipe organisatrice : Géodynamo

Salle pangée, Maison des Géosciences, 38400 Saint Martin d'Hères

Informations de visio :

https://univ-grenoble-alpes-fr.zoom.us/j/99652830364?pwd=NHRDUC9UaU5oVmE1aGJzTGhnNnEvUT09

ID de réunion : 996 5283 0364

Code secret : 389260