As part of an ongoing effort to create a publicly accessible GIS database that characterizes the global OTEC resource, more than two years of daily HYCOM (Hybrid Coordinate Ocean Model) temperature data were processed. This global dataset was used to estimate annual and seasonal averages of the temperature gradient between the sea surface and water at 1000 m depth, a parameter commonly used for quantifying OTEC potential. Periodic annual variation was also explored. At locations where the depth was less than 1000 m, the temperature difference was evaluated between the sea surface and near bottom water. These data show that the mean temperature difference can be as high as 26.5°C and commonly varies by less than 5°C annually. These HYCOM-based estimates were then compared against thermal profile measurements made during 58 sets of CTD casts performed off Southeast Florida.