The property of freshening in the AAIW region in the case of CE
is rather interesting. A probable explanation of this freshening can
be the lifting up of the pycnocline in the case of CE, causing further
intrusion of AAIW in the eddy region. This was well evident in our
vertical sections of temperature and salinity along 401S. In order to
see the reason of freshening of AAIW region in the ACE we used
the potential vorticity (PV) as a tracer in our calculation. The PV of
watermass is conserved unless it is modified by the surface
interactions and therefore at the depth levels of AAIW the PV
can be a useful tracer of watermass. Utilizing the methods
described in McCarthy and Talley (1999) (see Section 2) we
calculated the PV of eddies using our observations and Argo
profiles and results are projected onto neutral density levels
(Fig. 8). Here we assume that the properties of temperature and
salinity under eddy conditions are expected to be adjusted in such
a manner that the mean PV between eddy and non-eddy conditions
is conserved to the mean non-eddy conditions. We also
calculated the PV changes by adapting the climatological temperature
and/or salinity instead of their in-situ values in separate
cases. The PV between the 26.5 and 27 isopycnal surfaces were
examined in this way.