Minimize Oceanic Eddies

Back to Oceanic Phenomena


Since high-resolution images taken from satellites and space shuttles became available, oceanographers were quite surprised to learn that meso-scale and small-scale eddies or vortices are ubiquitous phenomena in coastal regions and at current fronts. Very spectacular images of small-scale eddies in coastal regions were acquired with a hand-held camera by the oceanographer-astronaut Scully-Power from the space shuttle Challenger during the Space Transportation System (STS) 41G mission in October 1984 (Scully-Power, 1986). However, such optical images can only be acquired during the day when there are no clouds and when the ocean is viewed at a favourable angle which is a function of the elevation and azimuth angle of the sun.

On the other hand, SAR can image eddies day and night and independent of cloud cover. Oceanic eddies become visible on optical and SAR images because the current field associated with the eddy modifies the sea surface roughness. The eddies become best visible on optical and radar images when the ocean surface is partially covered with surface films. These films are entrained by the flow associated with the eddy and accumulate in convergent regions where they reduce the sea surface roughness. Thus the surface films act as tracers for the flow field associated with the eddy. However, when the sea surface is completely covered with surface films, they lose their ability to trace the current field and the eddy becomes invisible.

Oceanic eddies can be generated by a variety of mechanism, e.g., (1) by local winds that are channeled by coastal geometry and topography, (2) by abrupt changes in wind speed and direction at atmospheric fronts, (3) by instabilities at oceanic current fronts, (4) by oceanic currents that interact with a headland, and (5) by water exchange through straits.

Vortex street generated in the laboratory


  • Arestegui, J., Tett, P. et al., The influence of island-generated eddies on chlorophyll distribution: study of mesoscale variation around Gran Canaria, Deep-Sea Res., 44, 71-96 (1997).
  • Fischer, J., Schott, F. & Stramma, L., Currents and transports of the Great Whirl - Socotra Gyre system during the summer monsoon, August 1993, J. Geophys. Res., 101, 3573-3587 (1996).
  • Grundling, M.L., Tracking eddies in the southeast Atlantic and southwest Indian Oceans with Topex/Poseidon, J. Geophys. Res., 100, 24977-24986 (1995).
  • Hsu, M-K., Mitnik, L.M., Lobanov, V.B., Liu, C.T. & Bulatov, N., Kuroshio front and oceanic phenomena near Taiwan and in the Southern Okhotsk Sea from ERS SAR data, Proc. 3rd ERS Symp., Florence, Italy, 17-21 March 1997, ESA publication SP-414, 1259-1266 (1997).
  • Hubert, L.F. & Krueger, A.F., Satellite pictures of mesoscale eddies, Monthly Weather Rev., November, 457-463 (1962).
  • Jensen, V.E., Samuel, P. & Johannessen, O.M., Mesoscale studies in the Indian Ocean using altimeter data. Proc. 3rd ERS Symp., Florence, Italy, 17-21 March 1997, ESA publication SP-414, 1279-1285.
  • Kirby, D.S., Barton, E.D., Mitchelson-Jacob, E.G. & Trasvina, A., Synthetic aperture radar (SAR) remote sensing of wind-driven circulation in the Gulf of Tehuantepec, Mexico , Proc. 3rd ERS Symp., Florence, Italy, 17-21 March 1997, ESA publication SP-414, 1273-1277 (1997).
  • Liu, A.K., Peng, C.Y. & Schumacher,J.D., Wave-current interaction study in the Gulf of Alaska for detection of eddies by synthetic aperture radar, J. Geophys. Res., 99, 10075-10085 (1994).
  • Lyzenga, D. & Wackerman, C., Detection and classification of ocean eddies using ERS-1 and aircraft SAR images, Proc. 3rd ERS Symp., Florence, Italy, 17-21 March 1997, ESA publication SP-414, 1267-1271 (1997).
  • Martinez-Diaz de Leon, A. & Robinson, I.S., Fronts and eddy features in coincident ERS-2 SAR and AVHRR-IR images for a case of offshore wind forcing, Proc. 3rd ERS Symp., Florence, Italy, 17-21 March 1997, ESA publication SP-414, 19971427-1431.
  • Martinez-Diaz de Leon, A., Robinson, I.S. & Ballestero, D., Wind driven ocean circulation features in the Gulf of Tehuantepec, Mexico, revealed by combined SAR and SST satellite sensor data, Int. J. Remote Sensing, 20, 1661-1668 (1999)
  • McWilliams, J.C., Submesoscale, coherent vortices in the ocean, Rev. of Geophys., 23, 165-182 (1985).
  • Mied, R.P., McWilliams, J.C. & Lindemann, G.J., The generation and evolution of mushroom-like vortices, J. Phys. Ocean., 21, 490-510 (1991).
  • Munk, W., Armi, L., Fischer, K. & Zachariasen, F., Spirals on the sea, Proc. R. Soc. Lond., 456, 1217-1280 (2000).
  • Scully-Power, P., Navy oceanographer shuttle observations: STS 41-G Mission Report, Naval Underwater Systems Center, Technical Report no. 7611 (1986).
  • Stumpf, H.G., Satellite detection of upwelling in the Gulf of Tehuantepec, J. Phys. Ocean., 5, 383-388 (1975).
  • Stumpf, H.G. & Legeckis, R.N., Satellite observations of mesoscale eddy dynamics in the Eastern Tropical Pacific Ocean, J. Phys. Ocean., 7, 648-658 (1977).
  • Swaters, G.E. & Mysak, L.A., Topographically-induced baroclinic eddies near a coastline, with application to the Northeast Pacific, J. Phys. Ocean., 15, 1470-1485 (1985).
  • Trasvina, A., Barton, E.D., Brown, J., Velez, H.S., Kosro, P.M. & Smith, R.L., Offshore wind forcing in the Gulf of Tehuantepec, Mexico: The asymmetric circulation, J. Geophys. Res., 100, 20649-20663 (1995).