In the case of the ACE, the PV significantly changed if we used
the climatological salinity than the in situ salinity, meaning that
in situ (which is fresher than the climatological salinity) salinity is
needed for maintaining a vorticity balance. With the climatological
salinity the ACE PV profiles assume the values of STMW, meaningthat the freshening of salinity in the AAIW is required to maintain
the mean PV structure in the ACE. On the other hand, the PV is
perturbed to a state of much deeper water if we replace the in situ
temperature by climatological values. Thus we may conclude that
the AAIW freshening in the ACE region occurs in such a way that
the PV is conserved to its mean or non-eddy conditions. However,
this conclusion neglects the role of relative vorticity and that is a
reasonable assumption especially at a depth of 800 m or below.
Such explanation of freshening of AAIW is also found applicable
for the CE albeit as weak perturbations in the PV (figure not
shown).