Spirals on the Sea: A Manifestation of Upper-Ocean Stirring

Abstract

Spiral eddies were first seen in the sun glitter on the Apollo Mission 30 years ago; they have since been recorded on SAR missions and in the infrared. The spirals are globally distributed, 10-25 km in size and overwhelmingly cyclonic. They have not been explained. Under light winds favorable to visualization, linear surface features with high surfactant density and low surface roughness are of common occurrence. We have proposed that frontal formations concentrate the ambient shear and prevailing surfactants Horizontal shear instabilities ensue when the shear becomes comparable to the Coriolis frequency. The resulting vortices wind the linear features into spirals. The hypothesis needs to be tested by prolonged measurements and surface truth. Spiral eddies are a manifestation of a submesoscale oceanography associated with upper ocean stirring; dimensional considerations suggest a horizontal diffusivity of order 10(exp 3) sq m/s.

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Document Details

Document Type
Technical Report
Publication Date
Jan 19, 2001
Accession Number
ADP013583

Entities

People

  • Laurence Armi
  • Walter Munk

Organizations

  • Scripps Institution of Oceanography

Tags

Communities of Interest

  • Air Platforms
  • Energy and Power Technologies
  • Space

DTIC Thesaurus Topics

  • Boundary Layer
  • Flow
  • Frequency
  • Images
  • Layers
  • Measurement
  • Mixing
  • Oceans
  • Shear Flow
  • Space Missions
  • Stagnation Point
  • Surface Roughness
  • Synthetic Aperture Radar
  • Turbulent Flow
  • Turbulent Mixing
  • Viscous Flow
  • Waves

Fields of Study

  • Environmental science

Readers

  • Astronomy/Astrophysics
  • Atmospheric Science / Meteorology, specifically Wind Wave Turbulence.
  • Coastal Oceanography