June 22, 1995

Dear EqPac ers,

A year ago we submitted to the JGOFS EqPac data base the mixed-layer depths
based on a density increase of 0.03 density units from surface values. 
This was the best fit for MLD compared to looking at the density profiles
and noting the depth of the first minor break in slope of sigma theta. 
This procedure was very sensitive to identifying the slight stratification
that resulted from daytime solar heating, especially in regions of colder
upwelled water.  This also lead to maximizing the diel variation in MLD. 
We still believe this is the best criterion for investigating short
time-scale processes in surface waters.  For investigating longer-term
processes, however, one might want to consider the MLD based on the
commonly used Levitus standard of an increase of 0.125 density units from
the surface value.  Both of these values are now posted in the JGOFS EqPac
data base for cruises TT007, TT008, TT011, and TT012 under the file named
MIXED.  

Regards,

Wilf Gardner