Impact of oceanic-scale interactions on the seasonal modulation of ocean dynamics by the atmosphere

Ocean eddies (with a size of 100–300 km), ubiquitous in satellite observations, are known to represent about 80% of the total ocean kinetic energy. Recent studies have pointed out the unexpected role of smaller oceanic structures (with 1–50 km scales) in generating and sustaining these eddies. The interpretation proposed so far invokes the internal instability resulting from the large-scale interaction between upper and interior oceanic layers. Here we show, using a new high-resolution simulation of the realistic North Pacific Ocean, that ocean eddies are instead sustained by a different process that involves small-scale mixed-layer instabilities set up by large-scale atmospheric forcing in winter. This leads to a seasonal evolution of the eddy kinetic energy in a very large part of this ocean, with an amplitude varying by a factor almost equal to 2. Perspectives in terms of the impacts on climate dynamics and future satellite observational systems are briefly discussed.

[1]  Marina Lévy,et al.  The influence of mesoscale and submesoscale heterogeneity on ocean biogeochemical reactions , 2013 .

[2]  Gurvan Madec,et al.  Impacts of sub-mesoscale physics on phytoplankton production and, subduction , 2001 .

[3]  S. Kobayashi,et al.  The JRA-25 Reanalysis , 2007 .

[4]  B. Fox‐Kemper,et al.  Parameterization of Mixed Layer Eddies. Part I. Theory and Diagnosis , 2008 .

[5]  A. Bracco,et al.  Submesoscale impacts on horizontal and vertical transport in the Gulf of Mexico , 2013 .

[6]  Patrice Klein,et al.  The oceanic vertical pump induced by mesoscale and submesoscale turbulence. , 2009, Annual review of marine science.

[7]  Yign Noh,et al.  Simulations of temperature and turbulence structure of the oceanic boundary layer with the improved near-surface process , 1999 .

[8]  J. Marshall,et al.  Scales, Growth Rates, and Spectral Fluxes of Baroclinic Instability in the Ocean , 2011 .

[9]  J. McWilliams,et al.  Cold filamentary intensification and oceanic surface convergence lines , 2009 .

[10]  Lee-Lueng Fu,et al.  Observing Oceanic Submesoscale Processes From Space , 2008 .

[11]  G. Dibarboure,et al.  Do Altimeter Wavenumber Spectra Agree with the Interior or Surface Quasigeostrophic Theory , 2008 .

[12]  J. McWilliams,et al.  Mesoscale to Submesoscale Transition in the California Current System. Part I: Flow Structure, Eddy Flux, and Observational Tests , 2008 .

[13]  N. Nakamura Scale Selection of Baroclinic Instability--Effects of Stratification and Nongeostrophy. , 1988 .

[14]  C. Wunsch,et al.  Ocean Circulation Kinetic Energy: Reservoirs, Sources, and Sinks , 2009 .

[15]  T. Özgökmen,et al.  Parameterization of particle transport at submesoscales in the Gulf Stream region using Lagrangian subgridscale models , 2012 .

[16]  Y. Sasai,et al.  Seasonal Mesoscale and Submesoscale Eddy Variability along the North Pacific Subtropical Countercurrent , 2014 .

[17]  James C. McWilliams,et al.  Statistical properties of decaying geostrophic turbulence , 1989, Journal of Fluid Mechanics.

[18]  B. Qiu,et al.  Upper-Ocean Heat Balance in the Kuroshio Extension Region , 1993 .

[19]  Raffaele Ferrari,et al.  A Frontal Challenge for Climate Models , 2011, Science.

[20]  Norman A. Phillips,et al.  Energy Transformations and Meridional Circulations associated with simple Baroclinic Waves in a two-level, Quasi-geostrophic Model , 1954 .

[21]  J. G. Charney,et al.  THE DYNAMICS OF LONG WAVES IN A BAROCLINIC WESTERLY CURRENT , 1947 .

[22]  Patrice Klein,et al.  Dynamics of the Upper Oceanic Layers in Terms of Surface Quasigeostrophy Theory , 2006 .

[23]  E. Campos,et al.  Submesoscale activity over the Argentinian shelf , 2008 .

[24]  Craig M. Lee,et al.  Statistics of vertical vorticity, divergence, and strain in a developed submesoscale turbulence field , 2013 .

[25]  James C. McWilliams,et al.  Mesoscale to submesoscale transition in the California current system. Part III: Energy balance and flux , 2008 .

[26]  Yongsheng Xu,et al.  The Effects of Altimeter Instrument Noise on the Estimation of the Wavenumber Spectrum of Sea Surface Height , 2012 .

[27]  R. Scott,et al.  Direct Evidence of an Oceanic Inverse Kinetic Energy Cascade from Satellite Altimetry , 2005 .

[28]  R. Lumpkin,et al.  Surface drifter pair spreading in the North Atlantic , 2010 .

[29]  Giulio Boccaletti,et al.  Mixed Layer Instabilities and Restratification , 2007 .

[30]  Yongsheng Xu,et al.  Global Variability of the Wavenumber Spectrum of Oceanic Mesoscale Turbulence , 2010 .

[31]  Gurvan Madec,et al.  Modifications of gyre circulation by sub-mesoscale physics , 2010 .

[32]  H. Sasaki,et al.  SSH Wavenumber Spectra in the North Pacific from a High-Resolution Realistic Simulation , 2012 .

[33]  B. Hoskins The role of potential vorticity in symmetric stability and instability , 1974 .

[34]  Patrice Klein,et al.  Impact of sub-mesoscale physics on production and subduction of phytoplankton in an oligotrophic regime , 2001 .

[35]  Y. Masumoto A fifty-year eddy-resolving simulation of the world ocean : Preliminary outcomes of OFES (OGCM for the Earth Simulator) , 2004 .

[36]  Peter H. Stone,et al.  On Non-Geostrophic Baroclinic Stability , 1966 .

[37]  T. Özgökmen,et al.  Seasonality of the submesoscale dynamics in the Gulf Stream region , 2013, Ocean Dynamics.

[38]  Adrian P. Martin,et al.  Bringing physics to life at the submesoscale , 2012 .

[39]  Kenji Komine,et al.  Description of Sea-Ice Component of Coupled Ocean - Sea-Ice Model for the Earth Simulator (OIFES) , 2005 .

[40]  Patrice Klein,et al.  Upper Ocean Turbulence from High-Resolution 3D Simulations , 2008 .