The Climatology and Variability of Eighteen Degree Water Potential
Vorticity Forcing
by Otmar Olsina
Master's defense
The input of potential vorticity (PV) over the North Atlantic
is estimated from observations to produce a climatological map of
PV flux and to study the interannual forcing variability.
Particular attention is paid to the North Atlantic subtropical
mode water potential temperature range from 17 to 19 ºC. The
sea surface PV flux is estimated through buoyancy and wind stress
contributions and using a climatological mixed layer depth
product. Wind forcing of PV is found to be weak. A
major observational subtropical mode water program named CLIMODE
was conducted during the winters of 2004 to 2006. These
years appear to be slightly stronger in their forcing than
climatology, although the difference is comparable to the
uncertainty. Attempts are made to relate the fluctuations to the
NAO, a major mode of North Atlantic atmospheric variability.