Darren, I emailed Dr. Mike McCormick  regarding  your query.  His
research focus includes Great Lakes water temperatures. Apparently there
isn't a lot of temperature info available... here is his response to my
email to him

"There exists precious little info on regular tz data over
time.  Most data are just sst plus any EBT that may be taken by various
vessels.  If such data existed it would be quite valuable.  Most
oceanographers using longer time series TZ data have gotten them from
weather ships which are no longer used."

If you are interested in communicating with him directly his email
address is:
[log in to unmask]

Good luck  in your search
--
```````````````````````````````````````
Margaret B. Lansing
National Oceanic and Atmospheric Administration
U.S. Department of Commerce
Great Lakes Environmental Research Lab
2205 Commonwealth Blvd.
Ann Arbor, MI 48105
734-741-2210 (office)
734-741-2289 (lab)
734-741-2055 (fax)
````````````````````````````````````````