Intense submesoscale upwelling in anticyclonic eddies

Observations from around the global ocean show that enhanced biological activity can be found in anticyclonic eddies. This may mean that upwelling of nutrient-rich water occurs within the eddy, but such upwelling is not captured by models that resolve mesoscale processes. High-resolution simulations presented here show intense submesoscale upwelling from the thermocline to the mixed layer in anticyclonic eddies. The properties of the upwelling are consistent with a process known as symmetric instability. A simple limiting nutrient experiment shows that this upwelling can drive much higher biological activity in anticyclonic eddies when there is a high nutrient concentration in the thermocline. An estimate for the magnitude of upwelling associated with symmetric instability in anticyclonic eddies in the Sargasso Sea shows that it may be of comparable magnitude to other processes, though further work is required to understand the full implications for basin-scale nutrient budgets.

[1]  W. Large,et al.  Oceanic vertical mixing: a review and a model with a nonlocal boundary layer parameterization , 1994 .

[2]  Nicholas R. Bates,et al.  Eddy/Wind Interactions Stimulate Extraordinary Mid-Ocean Plankton Blooms , 2007, Science.

[3]  D. Phinney,et al.  Rotary motions and convection as a means of regulating primary production in warm core rings. [of ocean currents] , 1985 .

[4]  R. Ferrari,et al.  On the equilibration of a symmetrically unstable front via a secondary shear instability , 2009, Journal of Fluid Mechanics.

[5]  J. R. Taylor,et al.  Ocean fronts trigger high latitude phytoplankton blooms , 2011 .

[6]  A. Verdière.  The Stability of Short Symmetric Internal Waves on Sloping Fronts: Beyond the Traditional Approximation , 2012 .

[7]  M. Follows,et al.  Ocean Dynamics and the Carbon Cycle: Principles and Mechanisms , 2011 .

[8]  Andrei P. Sokolov,et al.  A Three-Dimensional Ocean-Seaice-Carbon Cycle Model and its Coupling to a Two-Dimensional Atmospheric Model: Uses in Climate Change Studies , 2005 .

[9]  B. Fox‐Kemper,et al.  Langmuir–Submesoscale Interactions: Descriptive Analysis of Multiscale Frontal Spindown Simulations , 2014 .

[10]  L. Thomas,et al.  Destruction of Potential Vorticity by Winds , 2005 .

[11]  A. Mahadevan,et al.  Submesoscale processes and dynamics, In: Ocean Modeling in an Eddying, Regime (AGU Monograph), M. Hecht and H. Hasumi (Eds.) , 2008 .

[12]  B. Fox‐Kemper,et al.  Effects of submesoscale turbulence on ocean tracers , 2016 .

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

[14]  Thomas W. N. Haine,et al.  Gravitational, Symmetric, and Baroclinic Instability of the Ocean Mixed Layer , 1998 .

[15]  S. Bachman,et al.  Modelling of partially-resolved oceanic symmetric instability , 2014 .

[16]  Annette Samuelsen,et al.  Anticyclonic eddies in the Norwegian Sea; their generation, evolution and impact on primary production , 2010 .

[17]  A. Mahadevan,et al.  Comment on "Eddy/Wind Interactions Stimulate Extraordinary Mid-Ocean Plankton Blooms" , 2008, Science.

[18]  Y. Amitai,et al.  Long range transport of a quasi isolated chlorophyll patch by an Agulhas ring , 2011 .

[19]  L. Perelman,et al.  A finite-volume, incompressible Navier Stokes model for studies of the ocean on parallel computers , 1997 .

[20]  G. Flierl,et al.  Prediction of phytoplankton growth in response to the frictional decay of a warm‐core ring , 1986 .

[21]  David P. Marshall,et al.  The seasonal cycle of submesoscale flows , 2015 .

[22]  C. Eden,et al.  Effects of mesoscale eddy/wind interactions on biological new production and eddy kinetic energy , 2009 .

[23]  A. Oschlies,et al.  Internal-wave-induced and double-diffusive nutrient fluxes to the nutrient-consuming surface layer in the oligotrophic subtropical North Atlantic , 2004 .

[24]  Adrian P. Martin.  Phytoplankton patchiness: the role of lateral stirring and mixing , 2003 .

[25]  Christian E. Buckingham,et al.  Seasonality of submesoscale flows in the ocean surface boundary layer , 2016 .

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

[27]  C. Carlson,et al.  Carbon-cycle imbalances in the Sargasso Sea , 1994, Nature.

[28]  M. Follows,et al.  The Ekman transfer of nutrients and maintenance of new production over the North Atlantic , 1998 .

[29]  D. Chelton,et al.  Satellite observations of chlorophyll, phytoplankton biomass, and Ekman pumping in nonlinear mesoscale eddies , 2013 .

[30]  C. Wunsch,et al.  The hydrography of the North Atlantic in the early 1980s. An atlas , 1991 .

[31]  Larry W. O'Neill,et al.  Satellite Observations of Mesoscale Eddy-Induced Ekman Pumping , 2015 .

[32]  John Horne,et al.  Mesoscale Eddies Are Oases for Higher Trophic Marine Life , 2012, PloS one.

[33]  Patrice Klein,et al.  New production stimulated by high‐frequency winds in a turbulent mesoscale eddy field , 2009 .

[34]  M. Stern.  Interaction of a uniform wind stress with a geostrophic vortex , 1965 .

[35]  G. Flierl,et al.  Some Effects of the Wind on Rings , 1987 .

[36]  Mary Jane Perry,et al.  Eddy-driven subduction exports particulate organic carbon from the spring bloom , 2015, Science.

[37]  W. Dewar.  Mixed layers in gulf stream rings , 1986 .

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

[39]  Nicolas Gruber,et al.  Global patterns of marine nitrogen fixation and denitrification , 1997 .

[40]  R. Ferrari,et al.  Symmetric instability in the Gulf Stream , 2013 .

[41]  Craig M. Lee,et al.  Enhanced Turbulence and Energy Dissipation at Ocean Fronts , 2011, Science.

[42]  Andrew C. Thomas,et al.  Mesoscale eddies dominate surface phytoplankton in northern Gulf of Alaska , 2007 .

[43]  W. J. Jenkins,et al.  Seasonal oxygen cycling and primary production in the Sargasso Sea , 1985 .

[44]  J. R. Taylor,et al.  Reduction of the usable wind‐work on the general circulation by forced symmetric instability , 2010 .

[45]  J. McWilliams,et al.  Instability of an Axisymmetric Vortex in a Stably Stratified, Rotating Environment , 1998 .

[46]  B. Hoskins,et al.  Spirals in Potential Vorticity. Part I: Measures of Structure , 1998 .

[47]  Amit Tandon,et al.  Submesoscale Processes and Dynamics , 2013 .

[48]  Eric Shulenberger,et al.  The Pacific shallow oxygen maximum, deep chlorophyll maximum, and primary productivity, reconsidered , 1981 .

[49]  B. Fox‐Kemper,et al.  Symmetric and Geostrophic Instabilities in the Wave-Forced Ocean Mixed Layer , 2015 .

[50]  R. Ferrari,et al.  Frontogenesis, and the Stratification of the Surface Mixed Layer, , 2008 .