Autocorrelation of depth of the 14°C isotherm in the along- 

 shore traverse, leg two (fig. 13), showed a positive correlation 

 for lag intervals of a half-minute up to about 90 minutes (9 miles). 

 After 100-minute intervals, the correlation remained negative for 

 over 6-hour intervals. By comparison, the deeper 9°C isotherm 

 (fig. 14) gave a positive correlation for only 45 minutes, followed 

 by a negative correlation for about 2 hours, after which the cor- 

 relation again became slightly positive. This comparison indi- 

 cates that any dominant cycles in the 14°C isotherm are of longer 

 period than those in the 9°C isotherm. 



The results of the same correlation for the depths of the 16° 

 and 9°C isotherms, measured on the shoreward traverse, leg three 

 of the cruise, are given in figures 15 and 16. The depth correlation 

 for the 16 °C isotherm remained positive for over 2 hours whereas 

 that for the 9°C isotherm remained positive for 6 hours. Here the 

 dominant cycles are much longer than the period of computation. 



If the values of R remain positive, the long periods dominate 

 the spectrum which may be broad or narrow. In all cases the 

 major waves are of long period because the correlation does not 

 reach a maximum negative value for 220 and 90 minutes (figs. 13 

 and 14) and greater than 250 minutes for the data shown (figs. 12 

 and 16). The time interval to maximum negative value is half a 

 wave period. The minimum wave periods, then, for the most sig- 

 nificant correlations are for the 9°C alongshore waves and amount 

 to 180 minutes or 18 miles. The wave periods for the onshore and 

 offshore data runs are greater than 500 minutes or 50 miles. In 

 all cases the short-period waves are not consistent enough to out- 

 weigh the long -period ones, by this comparison. 



Power Spectrum of Depth Values 



The third method of representing variability is by the power 

 spectrum. 10 ' 13 ' 15 The power spectrum U(h) is given by the 

 Fourier transform of the autocorrelation, R . It is the energy per 

 unit bandwidth and thus designed to emphasize the dominant 



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