DATA 



All temperature-depth series were scaled from the tape every 30 seconds, and 

 values at the six levels v^^ere plotted and contoured in single-degree isotherms with 

 respect to depth and time. Data for 28 hours and 4 minuts are reproduced in 

 figures 3A to 14B, together with the times of occurrence of sea-surface slicks. 

 These times are indicated on the figures by heavy bars at the top and vertical 

 dashed lines. The horizontal scale is marked along the top and bottom at 5-minute 

 intervals. Since the time increases from left to right, the vertical fluctuations, com- 

 monly referred to as internal waves are moving from right to left. The vertical 

 scale marked on the left is depth in feet and runs from the surface to 35 feet. The 

 12 days of temperature structure and slicks are discussed below in chronological 

 order. 



12 June 1958 



Figure 3 represents the change of temperature structure with time off Mission 

 Beach on 12 June 1958, the first day of observations. The thermocline was stronger 

 and sharper than on subsequent days. The range of isotherms was from 66° to 

 53°F. The first drop in the thermocline amounted to about 15 feet in 2 minutes. 

 A long-duration slick (heavy band at surface) was located partly over the descend- 

 ing isotherm slope and partly over the narrow trough. The next vertical tempera- 

 ture excursion occurred 18 minutes later. It, too, was narrow compared to the 

 wave crest. The slick occurred over the upper part of the slope. 



Fifteen minutes later, a third depression passed the temperature-sensing unit. 

 Here, the slick occurred halfway on the slope as the isotherms dipped down. The 

 slope of the after side of the depression was steeper than that of the slick side. 

 At 1313, the temperature structure underwent a smaller oscillation without any 

 noticeable slick at the surface. This was followed by a narrow slick associated 

 with a little larger depression. The next slick was weak and broken. It lasted 2 

 minutes and just preceded a general dip in isotherms. Small fluctuations continued, 

 with a weak slick in the middle associated with one of the depressions. These 

 small oscillations continued and, finally, one short one was associated with a 

 broken or dissociated slick. The slicks were less distinct when the oscillations 

 were small and irregular. 



24 June 1958 



On the second day, 24 June (fig. 4A-B), the isotherms were nearly equally 

 spaced and extended nearly to the surface. The near-surface isotherm was 66° and 

 the temperature near the bottom of the graph was 55° at 35 feet. The first two 

 slicks occurred near the trough or depression in the thermocline. The next 

 occurred on the advancing slope. The next two were over minor crests, followed 

 by one each over a receding slope and trough. However, the next nine slicks 

 occurred on the receding slope of the internal waves created by the oscillating 

 thermocline. It appears that whenever the thermocline took a rapid descent, the 

 slick was characteristically on the descending slope. The following two were 

 broad, weak slicks over the forward side of the trough, and the last slick of this 

 long period fell characteristically over the receding side of the crest. 



