Intrinsic Variability of Sea Level from Global 1/12 degrees Ocean Simulations: Spatiotemporal Scales

• Published in: Journal of Climate
• Main Authors: Guillaume, Serazin, Penduff, T., Gregorio, S., Barnier, Bernard, Molines, J.-M., Terray, Laurent
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: Sea level; Altimetry; Ocean models; Interannual variability; Oceanic variability; [SDE]Environmental Sciences; Antarctic; Antarc*
• Online Access: https://insu.hal.science/insu-01205199; https://insu.hal.science/insu-01205199/document; https://insu.hal.science/insu-01205199/file/JOURNAL%20OF%20CLIMATE%20-%20%20Intrinsic%20Variability%20of%20Sea%20Level%20from%20Global%201-12%20degrees%20Ocean%20Simulations%20Spatiotemporal%20Scales.pdf; https://doi.org/10.1175/JCLI-D-14-00554.1

International audience In high-resolution ocean general circulation models (OGCMs), as in process-oriented models, a substantial amount of interannual to decadal variability is generated spontaneously by oceanic nonlinearities: that is, without any variability in the atmospheric forcing at these time scales. The authors investigate the temporal and spatial scales at which this intrinsic oceanic variability has the strongest imprints on sea level anomalies (SLAs) using a ° global OGCM, by comparing a “hindcast” driven by the full range of atmospheric time scales with its counterpart forced by a repeated climatological atmospheric seasonal cycle. Outputs from both simulations are compared within distinct frequency–wavenumber bins. The fully forced hindcast is shown to reproduce the observed distribution and magnitude of low-frequency SLA variability very accurately. The small-scale (L < 6°) SLA variance is, at all time scales, barely sensitive to atmospheric variability and is almost entirely of intrinsic origin. The high-frequency (mesoscale) part and the low-frequency part of this small-scale variability have almost identical geographical distributions, supporting the hypothesis of a nonlinear temporal inverse cascade spontaneously transferring kinetic energy from high to low frequencies. The large-scale (L > 12°) low-frequency variability is mostly related to the atmospheric variability over most of the global ocean, but it is shown to remain largely intrinsic in three eddy-active regions: the Gulf Stream, Kuroshio, and Antarctic Circumpolar Current (ACC). Compared to its ¼° predecessor, the authors’ ° OGCM is shown to yield a stronger intrinsic SLA variability, at both mesoscale and low frequencies.