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).
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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.
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It represents the sigmat = 27.2 surface quite well.
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The isotherm deepens
sharply from north to south across the current.
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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.
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Figure 12. Ensemble-averaged depth of the 10° isotherm as a
function of normal distance from the velocity maximum.
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