Publications des scientifiques de l'IRD

Cravatte Sophie, Serazin G., Penduff T., Menkès Christophe. (2021). Imprint of chaotic ocean variability on transports in the southwestern Pacific at interannual timescales. Ocean Science, 17 (2), p. 487-507. ISSN 1812-0784.

Titre du document
Imprint of chaotic ocean variability on transports in the southwestern Pacific at interannual timescales
Année de publication
2021
Type de document
Article référencé dans le Web of Science WOS:000631087900001
Auteurs
Cravatte Sophie, Serazin G., Penduff T., Menkès Christophe
Source
Ocean Science, 2021, 17 (2), p. 487-507 ISSN 1812-0784
The southwestern Pacific Ocean sits at a bifurcation where southern subtropical waters are redistributed equatorward and poleward by different ocean currents. The processes governing the interannual variability of these currents are not completely understood. This issue is investigated using a probabilistic modeling strategy that allows disentangling the atmospherically forced deterministic ocean variability and the chaotic intrinsic ocean variability. A large ensemble of 50 simulations performed with the same ocean general circulation model (OGCM) driven by the same realistic atmospheric forcing and only differing by a small initial perturbation is analyzed over 1980-2015. Our results show that, in the southwestern Pacific, the interannual variability of the transports is strongly dominated by chaotic ocean variability south of 20 degrees S. In the tropics, while the interannual variability of transports and eddy kinetic energy modulation are largely deterministic and explained by the El Nino-Southern Oscillation (ENSO), ocean nonlinear processes still explain 10% to 20% of their interannual variance at large scale. Regions of strong chaotic variance generally coincide with regions of high mesoscale activity, suggesting that a spontaneous inverse cascade is at work from the mesoscale toward lower frequencies and larger scales. The spatiotemporal features of the low-frequency oceanic chaotic variability are complex but spatially coherent within certain regions. In the Subtropical Countercurrent area, they appear as interannually varying, zonally elongated alternating current structures, while in the EAC (East Australian Current) region, they are eddy-shaped. Given this strong imprint of large-scale chaotic oceanic fluctuations, our results question the attribution of interannual variability to the atmospheric forcing in the region from pointwise observations and one-member simulations.
Plan de classement
Sciences fondamentales / Techniques d'analyse et de recherche [020] ; Limnologie physique / Océanographie physique [032]
Description Géographique
PACIFIQUE
Localisation
Fonds IRD [F B010081123]
Identifiant IRD
fdi:010081123
Contact