Spirals on the sea

Spiral eddies were first seen in the sunglitter on the Apollo Mission 30 years ago; they have since been recorded on synthetic aperture radar (SAR) images and in the infrared. We present a small sample of images. The spirals are broadly distributed over the world's oceans, 10–25 km in size and overwhelmingly cyclonic. Under light winds favourable to visualization, linear surface features with high surfactant density and low surface roughness are of common occurrence. The linear features are wound into spirals in vortices associated with horizontal shear instability, modified by rotation, in regions where the shear is comparable with the Coriolis frequency. Two models for concentrating shear are presented: a softened version of the classical sharp Margules front, and the time–dependent Lagrangian model of Hoskins & Bretherton. Horizontal shear instabilities and both frontal models favour cyclonic shear and cyclonic spirals, but for different reasons.

[1]  P. Orlandi,et al.  Evolution of isolated vortices in a rotating fluid of finite depth , 1999, Journal of Fluid Mechanics.

[2]  Rudnick,et al.  Compensation of horizontal temperature and salinity gradients in the ocean mixed layer , 1999, Science.

[3]  W. Peltier,et al.  Three-dimensional instability of anticyclonic swirling flow in rotating fluid: Laboratory experiments and related theoretical predictions , 1998 .

[4]  Ola M. Johannessen,et al.  COASTWATCH'95: ERS 1/2 SAR detection of natural film on the ocean surface , 1998 .

[5]  Marina I. Mityagina,et al.  Investigation of perturbing action of atmospheric and internal oceanic processes on the waved sea surface using ocean remote sensing data , 1998, IEEE Oceanic Engineering Society. OCEANS'98. Conference Proceedings (Cat. No.98CH36259).

[6]  George O. Marmorino,et al.  Measurement of surface currents using sequential synthetic aperture radar images of slick patterns near the edge of the Gulf Stream , 1998 .

[7]  W. Peltier,et al.  Stratification effects on the stability of columnar vortices on the f-plane , 1998, Journal of Fluid Mechanics.

[8]  D. Rudnick.  Intensive surveys of the Azores Front: 2. Inferring the geostrophic and vertical velocity fields , 1996 .

[9]  D. Rudnick,et al.  Intensive surveys of the Azores Front 1. Tracers and dynamics , 1996 .

[10]  T. Evans,et al.  On vorticity shedding by unstable jets , 1994 .

[11]  William M. Balch,et al.  A line in the sea , 1994, Nature.

[12]  L. Polvani,et al.  The coherent structures of shallow-water turbulence: Deformation-radius effects, cyclone/anticyclone asymmetry and gravity-wave generation. , 1994, Chaos.

[13]  Keita Iga.  Reconsideration of Orlanski's instability theory of frontal waves , 1993, Journal of Fluid Mechanics.

[14]  Steven G. Ackleson,et al.  Natural Oil Slicks in the Gulf of Mexico Visible From Space , 1993 .

[15]  D. Etling,et al.  Roll vortices in the planetary boundary layer: A review , 1993 .

[16]  M. Page,et al.  Flow past a circular cylinder on a β-plane , 1993, Journal of Fluid Mechanics.

[17]  D. Tritton,et al.  The structure of a turbulent free shear layer in a rotating fluid , 1992, Journal of Fluid Mechanics.

[18]  D. J. Tritton,et al.  Stabilization and destabilization of turbulent shear flow in a rotating fluid , 1992, Journal of Fluid Mechanics.

[19]  O. M. Griffin,et al.  High‐resolution measurement of surface‐active film redistribution in ship wakes , 1992 .

[20]  P. Cho,et al.  Synthetic aperture radar observations of currents colocated with slicks , 1992 .

[21]  M. Lesieur,et al.  Stabilizing and destabilizing effects of a solid‐body rotation on quasi‐two‐dimensional shear layers , 1991 .

[22]  G. Flierl,et al.  Experimental observations of baroclinic eddies on a sloping bottom , 1990 .

[23]  J. Moum,et al.  Sea slicks and surface strain , 1990 .

[24]  E. Kasischke,et al.  An overview of the SAR Internal Wave Signature Experiment , 1988 .

[25]  E. Svendsen,et al.  Ice-Edge Eddies in the Fram Strait Marginal Ice Zone , 1987, Science.

[26]  P. Scully-Power.  Navy Oceanographer Shuttle Observations, STS 41-G Mission Report , 1986 .

[27]  T. Gerling.  Structure of the surface wind field from the Seasat SAR , 1986 .

[28]  R. Bernstein,et al.  Large horizontal surface velocity shears in the ocean obtained from images of refracting swell and in situ moored current data , 1985 .

[29]  Hsien-Wang Ou.  Geostrophic Adjustment: A Mechanism for Frontogenesis , 1984 .

[30]  G. M. Corcos,et al.  The mixing layer: deterministic models of a turbulent flow. Part 1. Introduction and the two-dimensional flow , 1984, Journal of Fluid Mechanics.

[31]  T. W. Thompson,et al.  Synthetic aperture radar observation of ocean roughness from rolls in an unstable marine boundary layer , 1983 .

[32]  Ola M. Johannessen,et al.  Oceanographic conditions in the marginal ice zone north of Svalbard in early fall 1979 with an emphasis on mesoscale processes , 1983 .

[33]  A. E. Gill.  Atmosphere-Ocean Dynamics , 1982 .

[34]  D. Boyer,et al.  Flow past a circular cylinder on a β-plane , 1982, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[35]  Robert A. Brown.  Longitudinal instabilities and secondary flows in the planetary boundary layer: A review , 1980 .

[36]  M. Macvean,et al.  Redistribution of scalars during upper ocean frontogenesis:A numerical model , 1980 .

[37]  G. M. Corcos,et al.  Vorticity concentration and the dynamics of unstable free shear layers , 1976, Journal of Fluid Mechanics.

[38]  A. Roshko,et al.  On density effects and large structure in turbulent mixing layers , 1974, Journal of Fluid Mechanics.

[39]  F. Browand,et al.  Vortex pairing : the mechanism of turbulent mixing-layer growth at moderate Reynolds number , 1974, Journal of Fluid Mechanics.

[40]  C. W. Newton,et al.  Atmospheric circulation systems: their structure and physical interpretation , 1969 .

[41]  T. Pedley.  On the instability of viscous flow in a rapidly rotating pipe , 1969, Journal of Fluid Mechanics.

[42]  I. Orlanski.  Instability of Frontal Waves. , 1968 .

[43]  F. Bretherton,et al.  Wavetrains in inhomogeneous moving media , 1968, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[44]  J. T. Stuart.  On finite amplitude oscillations in laminar mixing layers , 1967, Journal of Fluid Mechanics.

[45]  D. F. Hays,et al.  Table of Integrals, Series, and Products , 1966 .

[46]  W. Munk,et al.  Measurement of the Roughness of the Sea Surface from Photographs of the Sun’s Glitter , 1954 .

[47]  G. Ewing.  Relation between Band Slicks at the Surface and Internal Waves in the Sea , 1950, Science.

[48]  A. H. Woodcock.  Soaring over the Open Sea , 1942 .

[49]  C. Rossby,et al.  On the Mutual Adjustment of Pressure and Velocity Distributions in Certain Simple Current Systems, II , 1938 .

[50]  A. Murray.  Mineral Resources of Newfoundland , 1880, Nature.

[51]  P. Flament,et al.  The Shear, Convergence, and Thermohaline Structure of a Front* , 2000 .

[52]  R. Hide.  On the effects of rotation on fluid motions in cylindrical containers of various shapes and topological characteristics , 1998 .

[53]  S. A. Thorpe,et al.  Dynamical processes of transfer at the sea surface , 1995 .

[54]  J. G. Bruce.  Eddies southwest of the Denmark Strait , 1995 .

[55]  P. Flament,et al.  Amplitude and Horizontal Structure of a Large Diurnal Sea Surface Warming Event during the Coastal Ocean Dynamics Experiment , 1994 .

[56]  Sidney Leibovich,et al.  The form and Dynamics of Langmuir Circulations , 1983 .

[57]  Francis P. Bretherton,et al.  Atmospheric Frontogenesis Models: Mathematical Formulation and Solution , 1972 .

[58]  O. Phillips.  The dynamics of the upper ocean , 1966 .

[59]  T. Bergeron,et al.  Physikalische Hydrodynamik: Mit Anwendung auf die Dynamische Meteorologie , 1933 .