Ocean–Atmosphere Interactions - Ocean in the Earth System - page 132

3.3.2. Surface temperature fronts
Regions of surface temperature (SST) horizontal gradients are
called oceanic fronts. They are associated with a current or an eddy,
and often reinforced by the sinking of surface water or the rising of
water from the subsurface on one side of the front. These structures
are, therefore, very common all around the globe, but with a high SST
gradient variability, ranging from a few tenths of a degree to more
than 10°C per 100 km for intense fronts.
For a long time, these phenomena have been neglected. The reason
is that they remained unknown until the launch of space-borne fine
resolution Infrared (IR) instruments around the end of the 1970s (see
Figure 3.5). Moreover, global atmospheric and oceanic models have
only recently been capable of representing such small-medium-scale
phenomena, which were previously smoothed.
Figure 3.5. Example of the detection of SST fronts using satellite images in infrared:
an algorithm determines the probability for these fronts to occur, on average over
the three months of winter (from [BEL 03]). The [CAY 92] algorithm is used
(see color section)
C OMMENTARY ON F IGURE 3.5.- There is a strong likelihood of fronts
occurring in the vicinity of large currents, and at the Equator, where