Thermal structure

By projecting the XBTs into the same stream coordinate system as used for the upper-ocean velocity, we obtain a matching thermal description of the current. The ensemble-averaged depth of the 10° C isotherm is shown in Figure 12(below).

  • This isotherm lies just below the reach of the seasonal thermocline near the Gulf Stream such that salinity remains invariant in time and essentially constant across the Gulf Stream.
  • It represents the sigmat = 27.2 surface quite well.
  • The isotherm deepens sharply from north to south across the current.
  • If we fit an exponential to the initial deepening (y < 0), we obtain a scale-width of 19 km (dashed line), which agrees reasonably well with the estimates from the velocity field.
Figure 12. Ensemble-averaged depth of the 10° isotherm as a function of normal distance from the velocity maximum.