[Lessismore]

Check out http://caribjsci.org/june98/Biggs.pdf

Figure 1 gives a topographic map of the sea floor in the Yucatan Straits. It is about 2000 meters deep.

Your calculations don't include an estimate of precipitation over the Gulf of Mexico. The net evaporation may be a lot smaller than 1 m/yr.

[blam]

"Your calculations don't include an estimate of precipitation over the Gulf of Mexico. "

My instincts are that precipitation levels would have been much reduced during the Ice Age. I could not get the url to work.