Float 5900097 (Fig. 12 centre) spen

Float 5900097 (Fig. 12 centre) spent nearly three years in a
region with a very large salinity gradient. Throughout its life
it experienced sudden changes of up to 0.06 in the minimum
salinity at AAIW level. It might be tempting to suspect instrumental
instability or temporary fouling of the conductivity
cell; but inspection of the temperature-salinity (TS-) diagram
for the float (not shown) verifies that the cell performed
without problems and that the float encountered two varieties
of AAIW with different salinity minimum values. The TSdiagram
gives additional support for the presence of a front
between the two varieties by showing that profiles taken near
the transition between the two varieties often display double
salinity minima indicative of layering and intrusions across
the front. The discussion of Sect. 4.5 will address double
minima in more detail.