Near-surface velocity and PV structure of the Gulf Stream
Abstract >> Introduction >> Data >> Velocity Structure >> Potential Vorticity Structure >> Eddy Exchange Processes >> Discussion and Conclusions



Shipboard Acoustic Doppler Current Profiler Data

  • The Oleander has been collecting velocity data during its weekly roundtrips between Bermuda and New Jersey since the Fall of 1992.
  • These sections provide exceptional resolution of the upper ocean velocity field: 8 meters in the vertical and 2.4 km in the horizontal (5 minute averaging at 16 Kt vessel speed).
  • Since 1995 a differential GPS receiver has corrected for the effects of deliberate degrading of GPS navigation (selective availability; a.k.a. dithering).
  • Since 1995 we also operate a heading GPS system (3D-GPS) which allows us to correct the gyro compass error directly to a heading accuracy of ± 0.1°. (An error of 1° introduces a 0.14 m/s error in cross-track velocity with a vessel speed of 16 Kts.)
  • Under good operating conditions we think the velocities are accurate at the ± 0.03 m/s level.

XBT Data

  • At the beginning of every month an XBT survey occurs across the shelf, the Slope Sea and the Gulf Stream on the outbound leg and some additional XBTs in the Sargasso Sea on the return leg.
  • The horizontal resolution of the XBTs varies and depends upon location. In the Gulf Stream profiles are taken about every 25 km.
  • The once a month sampling means that only one out of eight crossings will have XBTs and depending upon the weather the concurrent ADCP data may or may not be very useful. Thus the number of sections with simultaneous good XBT and ADCP coverage of the core of the Gulf Stream is significantly less than the total number of sections available for analysis.

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