Clark and Yarnall 



no more than the weak statement that cross-channel currents must 

 remain under consideration as a possible significant contributor to 

 the tidally related signatures in H43 phase. 



If we consider the effect of the same current situation at 

 H3 we calculate a peak to peak phase change of 0.04 cycles. This 

 number is not comparable to measured values which are on the order 

 of 5 cycles. There is a sufficient discrepancy to rule against a 

 dominant cross- channel current contribution to the tidal phase fluc- 

 tuation at H3 . 



The situation is obviously complex at both hydrophones. 

 Rather than pursue further marginal calculations, the authors prefer 

 to await more thorough analysis of the available data and additional 

 experimental results. It has been a consistent theme of this discus- 

 sion that the tidal signatures are related to phenomena that, to a 

 large measure, are spatially coherent throughout the propagation path. 

 It is perhaps on this scale of events that the synoptic "sampling" 

 obtained along the acoustic propagation path offers the greatest 

 promise for environmental studies. The possibilities of the acoustic 

 probe are apparent. However, only limited conclusions can be drawn 

 unless the acoustic measurements at H43 are "calibrated" by direct 

 environmental measurements of the type provided by the 100 meter 

 thermistor string for the H3 propagation path. It seems likely, at 

 this point, that a modest increase in field instrumentation will 

 calibrate the H3 path to the extent that certain environmental effects 

 could be quantitatively related to the acoustic data. This premise 

 will receive additional support in the next section of the paper. The 

 extent to which this can be accomplished for the full path to H43 is 

 an intriguing question that will also be considered after the long 

 period acoustic signatures are discussed. 



LONG PERIOD SIGNATURES - ATMOSPHERIC PHENOMENA 



One of the most striking results of LCT-1 was the divergent 

 behavior of signal phase at H3 and H43 (Fig. 13) . At H43 the long 

 trend was consistently downward with a net change of more than 250 

 cycles over the length of the test. At H3 the trend was also down- 

 ward until near the end of October; at that time the trend was re- 

 versed by a series of "step function" phase advances. Similar effects 

 are likely to be present in the H43 data, but are not of sufficient 

 magnitude to dominate the H43 phase curve. We will confine our at- 

 tention initially to the H3 data. A geophysical explanation, related 

 to the local passage of polar fronts, can be offered for the "step 

 function" signatures at this hydrophone. The hypothesis is supported 

 by the evidence of the environmental data. 



Local passage of an atmospheric cold front is marked by an 

 abrupt shift to relatively strong northerly winds. The consequences 

 for the Straits of Florida water will include: 



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