605 



FIGURE 10. Showing the spread of a front, 

 formed by withdrawing a barrier from the center 

 of an experimental tank. The initial state cor- 

 responded to "run down" fingers, with extra 

 (dyed) sugar solution mixed in at the left. 

 Upper: 2-1/2 mins . after barrier was removed, 

 showing intrusions formed by the den- 

 sity adjustment. 

 Lower: 55 mins. after barrier removed, showing 

 the smaller scale motions driven by 

 double-diffusive processes across the 

 frontal region. 



[Joyce (1977) ] to parameterize the effective 

 increase in the horizontal diffusion of T and S, 

 produced by interleaving, in terms of the horizontal 

 gradients and these quasi-vertical fluxes. 



ACKNOWLEDGMENT 



I am grateful to R. Wylde-Browne for his assistance 

 with many of the recent experiments described here, 

 and particularly with the photography. Discussions 

 with R. W. Griffiths and B. R. Ruddiclc about their 

 current work have been very stimulating. 



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