Temperature measurements made 9 km west of a prominent sill in Massachusetts Bay indicate that the seasonal thermocline heaves up and down in phase with periods of 6 to 8 minutes for about 2.5 hours during flood tide. A sudden rise in the general temperature level accompanies the onset of the short-period motion....
Halpern, David. 1971. "Observations on short-period internal waves in Massachusetts Bay." Journal of Marine Research 29, (2). https://elischolar.library.yale.edu/journal_of_marine_research/1206