Internal waves of tidal period off southern California

Three 24-hour multiple-ship surveys, each ship lowering a bathythermograph at 15-minute intervals, revealed the presence of internal waves off southern California. The waves had the form of vertical fluctuations of temperature of up to 90 feet over a wide range of frequencies dominated by an approximate semidiurnal period. They appeared to be roughly parallel to the top of the continental slope and to move shoreward at a speed of about 7 knots in deep water and less than 1 knot over the shallow shelf. There may be evidence of internal surf as the waves approach the coast.