Chaotic Variability of Ocean: Heat Content Climate-Relevant Features and Observational Implications

Type Publication
Acceptance Date 2018-06 IN PRESS
Language English
Copyright The Oceanography Society
Author(s) Penduff T.1, Serazin G.2, Leroux S.3, Close S.4, Molines J.-M.4, Barnier B.4, Terray L.5, Maze GuillaumeORCID6
Affiliation(s) 1 : CNRS, IGE-MEOM, UGA CS 40 700, Grenoble, France
2 : Laboratoire d’Études en Géophysique et Océanographie Spatiales, OMP, Toulouse, France
3 : Ocean Next, Grenoble, France
4 : Université Grenoble Alpes, CNRS, IRD, Grenoble INP, Institut des Géosciences de l’Environnement, Grenoble, France
5 : CNRS/CERFACS, CECI UMR 5318, Toulouse, France
6 : Ifremer, Université de Brest, CNRS, IRD, Laboratoire d’Oceìanographie Physique et Spatiale, IUEM, Plouzaneì, France
Source Oceanography (1042-8275) (The Oceanography Society) In Press
DOI 10.5670/oceanog.2018.210
Abstract

Global ocean models that admit mesoscale turbulence spontaneously generate a substantial interannual-to-multidecadal chaotic intrinsic variability in the absence of atmospheric forcing variability at these timescales. is phenomenon is substantially weaker in non-turbulent ocean models but provides a marked stochastic avor to the low-frequency variability in eddying ocean models, which are being cou- pled to the atmosphere for next-generation climate projections. In order to disentangle the atmospherically forced and intrinsic ocean variabilities, the OCCIPUT (OceaniC Chaos – ImPacts, strUcture, predicTability) project performed a long (1960–2015), large ensemble (50 members) of global ocean/sea ice 1/4° simulations driven by the same atmospheric reanalysis, but with perturbed initial conditions. Subsequent ensem- ble statistics show that the ocean variability can be seen as a broadband “noise,” with characteristic scales reaching multiple decades and basin sizes, locally modulated by the atmospheric variability. In several mid-latitude regions, chaotic processes have more impact than atmospheric variability on both the low-frequency variability and the long-term trends of regional ocean heat content. Consequently, certain climate- relevant oceanic signals cannot be unambiguously attributed to atmospheric variabil- ity, raising new issues for the detection, attribution, and interpretation of oceanic heat variability and trends in the presence of mesoscale turbulence.

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