Michael Gregg  
   Principal Investigator

   Matthew Alford  
   Co-Principal Investigator

   Andrey Shcherbina  
   Post-Doctoral Researcher

   Ramsey Harcourt  
   Co-Principal Investigator


Thermohaline intrusions are formed by localized penetration of one water mass into another (typically across a front). The term "intrusions" is traditionally reserved for the features of limited vertical extent which are still attached to their water mass of origin. (Other examples of mutual water mass penetration being filaments, lenses, eddies, etc.) Frontal intrusions are one of the crucial building blocks of lateral dispersion of heat, salt, nutrients, and other tracers in the ocean.

  • Locate intrusions and determine their cross-front characteristics
  • Determine the 3D structures of intrusions and how they relate to the front
  • Follow the evolution of several intrusions in a Lagrangian frame
  • Observe the formation of one or more intruions


A field study of the interleaving features in the Subtropical Frontal Zone (STFZ) of the North Pacific near 31°N, 158°W was conducted from 5 to 29 July 2007 onboard the R/V Wecoma.

This "STF07" experiment encompassed:
  • Hydrographic surveying with a towed depth-cycling conductivity-temperature-depth (CTD) platform SWIMS
  • Microstructure profiling
  • Shipboard velocity observations
  • Lagrangian float releases

Map of the STF07 survey 5–29 July 2007.


During the STF07 experiment, we mapped three-dimensional structure of several prominent intrusions. Particular shapes observed included broad sheets and narrow tongues, extending towards the warm and salty side of the thermohaline fronts.

Perspective view of a 35.0 isohaline on 14 July 2007: an example of a "broad-sheet" intrusion.

Perspective view of a 34.8 isohaline on 23 July 2007: an example of a "multiple-tongue" intrusion.


Shcherbina, A.Y., M.C. Gregg, M.H. Alford, M.H., and R.R. Harcourt, "Three-dimensional structure and temporal evolution of submesoscale thermohaline intrusions in the North Pacific subtropical frontal zone," J. Phys. Oceanogr., 40, 1669-1689, doi:10.1175/2010JPO4373.1, 2010.

Shcherbina, A.Y., M.C. Gregg, M.H. Alford, and R.R. Harcourt, "Characterizing thermohaline intrusions in the North Pacific subtropical frontal zone," J. Phys. Oceanogr., 39, 2735-2756, doi: 10.1175/2009JPO4190.1, 2009.


The hydographic survey was conducted with the Shallow Water Mapping System (SWIMS), a depth-cycling towed instrument platform. SWIMS was towed, typically at 6 kt, undulating between two predetermined depths within the upper 200 m. Continuous SWIMS CTD time series were split into individual up- and down-cast profiles, and interpolated onto a uniform 0.5-m vertical grid. Tow patterns included long straight sections, "radiator," and star-shaped patterns. A total of 32 patterns or "groups" were executed, with over 11,000 profiles spanning a cumulative survey length of 4,500 km.

Each of the MAT files in the .zip directory corresponds to approximately 3 hours of the survey.
Zipped directory of data files – 305 MB

Please refer to the index file (8 KB) to obtain the time period covered in each file.