Localization of Deep Ocean Convection by a Mesoscale Eddy

Abstract Observations of open-ocean deep convection indicate that it is a highly localized phenomenon, occurring over areas of tens of kilometers in diameter. The cause of this localization has been ascribed to “preconditioning”—the local weakening of the stable density stratification associated with upwardly domed isopycnal surfaces in a surface-intensified cyclonic circulation. However, most numerical and laboratory studies of localized convection have prescribed the localization artificially, by confining the surface buoyancy loss to a circular disk. In contrast, in the numerical simulations described here, deep convection forced by horizontally uniform buoyancy loss is localized within a region of initially weaker stratification than its surroundings. The preconditioned region is associated with a cold-core cyclonic eddy in geostrophic and cyclostrophic balance. As in previous studies of disk-shaped cooling, the localized convection region undergoes baroclinic instability at late times, causing the br...

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

[2]  John Whitehead,et al.  Localized convection in rotating stratified fluid , 1996 .

[3]  S. Legg,et al.  A Heton Perspective of Baroclinic Eddy Transfer in Localized Open Ocean Convection , 1996 .

[4]  John Marshall,et al.  Dynamics of isolated convective regions in the ocean , 1996 .

[5]  P. Delecluse,et al.  Large-Scale Preconditioning of Deep-Water Formation in the Northwestern Mediterranean Sea , 1996 .

[6]  Uwe Send,et al.  Observations of Deep Convection in the Gulf of Lions, Northern Mediterranean, during the Winter of 1991/92 , 1996 .

[7]  John R. Taylor,et al.  Unsteady, Turbulent Convection into a Rotating, Linearly Stratified Fluid: Modeling Deep Ocean Convection , 1995 .

[8]  D. Brickman.  Heat Flux Partitioning in Open-Ocean Convection , 1995 .

[9]  J. Fischer,et al.  Preconditioning the Greenland Sea for deep convection: Ice formation and ice drift , 1995 .

[10]  K. Alverson.  Topographic preconditioning of open ocean deep convection , 1995 .

[11]  J. Marshall,et al.  Integral Effects of Deep Convection , 1995 .

[12]  F. Schott,et al.  Observation of a deep convection regime with acoustic tomography , 1995 .

[13]  P. Worcester,et al.  Thermal evolution of the Greenland Sea Gyre in 1988–1989 , 1995 .

[14]  John R. Taylor,et al.  Convectively driven mixed layer growth in a rotating, stratified fluid , 1995 .

[15]  T. Maxworthy,et al.  Unsteady, Turbulent Convection into a Homogeneous, Rotating Fluid,with Oceanographic Applications , 1994 .

[16]  John Marshall,et al.  Convection with Rotation in a Neutral Ocean: A Study of Open-Ocean Deep Convection , 1993 .

[17]  P. Delecluse,et al.  A Three-Dimensional Numerical Study of Deep-Water Formation in the Northwestern Mediterranean Sea , 1991 .

[18]  F. Schott,et al.  Hydrographic Structure of the Convection Regime in the Gulf of Lions: Winter 1987 , 1991 .

[19]  Kevin D. Leaman,et al.  Observations with Moored Acoustic Doppler Current Profilers in the Convection Regime in the Golfe du Lion , 1991 .

[20]  P. Gent,et al.  A numerical model of the balance equations in a periodic domain and an example of balanced turbulence , 1986 .

[21]  J. Pedlosky.  The Instability of Continuous Heton Clouds , 1985 .

[22]  R. Clarke,et al.  The Formation of Labrador Sea Water. Part II. Mesoscale and Smaller-Scale Processes , 1983 .

[23]  R. Clarke,et al.  The Formation of Labrador Sea Water. Part I: Large-Scale Processes , 1983 .

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

[25]  J. Swallow,et al.  The preconditioning phase of MEDOC 1969—I. Observations , 1973 .

[26]  N. Hogg.  The preconditioning phase of MEDOC 1969—II. Topographic effects , 1973 .

[27]  H. Lacombe,et al.  Observation of Formation of Deep Water in the Mediterranean Sea, 1969 , 1970 .

[28]  E. T. Eady,et al.  Long Waves and Cyclone Waves , 1949 .

[29]  J. McWilliams,et al.  Penetrative convection in rapidly rotating flows: preliminary results from numerical simulation , 1996 .

[30]  A. Lascaratos.  Estimation of deep and intermediate water mass formation rates in the Mediterranean Sea , 1993 .

[31]  Medoc Group.  Observation of Formation of Deep Water in the Mediterranean Sea, 1969 , 1970, Nature.

[32]  Katsuyuki V. Ooyama,et al.  On the Stability of the Baroclinic Circular Vortex: a Sufficient Criterion for Instability. , 1966 .

[33]  S. Chandrasekhar.  Hydrodynamic and Hydromagnetic Stability , 1961 .