The hydrography of the Gulf of Venezuela 



127 



for the semi-diurnal tides across the entrance to the Gulf at a longitude intermediate 

 between Aruba and Las Piedras. The amplitude of the M, component is increased 

 eightfold, and the sums of the semi-diurnal components sixfold as the result of the 

 resonance. 



72" 71° l(f 



Fig. 11. Oxygen under saturation at 1 metre depth in Gulf of Venezuela 



Since enough water must cross the sill of Calabozo Bay, having a depth of 18 metres, 

 to raise and lower the level of the Bay nearly one metre twice daily, it is evident that 

 strong tidal currents are to be expected over the sill. These currents, combined with 

 the wind, account for the mixing which appears to occur in this region. 



Water Levels 



The monthly mean tide levels at Las Piedras change by as much as 0-8 feet in the 

 course of the year (Fig. 12, A). The pattern is similar to that observed at positions on 

 the Atlantic coast south of Chesapeake Bay and in the Gulf of Mexico (Marmer, 

 1951), and evidently is part of widespread phenomena. The monthly mean tide levels 

 at Zaparita Island follow a similar pattern, but the annual variation in level is only 

 0-4 feet. 



The mean annual difference in water level across the Gulf of Venezuela, between 

 Las Piedras and Zaparita Island, is 0-92 feet in a distance of 93 nautical miles. The 



