SUMMARY 235 



SUMMARY 



The Royal Research Ship ' William Scoresby ' visited the west coast in the southern 

 winter of 1931, the object of her enquiry being the Peru Coastal Current. Observations 

 on temperature, salinity, oxygen and phosphate from surface to bottom, and collections 

 of phyto- and zooplankton in the upper layers were undertaken as a routine. 



DEVIATION OF COASTAL WINDS 



Wind observations are analysed and compared with earlier records (pp. 121-4 

 and Fig. 4). North of 40° S, coastal winds blow parallel to the shore, showing a devia- 

 tion from the south-east direction typical of this sector of the South Pacific anticyclonic 

 high-pressure area. The importance of the Andean barrier is stressed. Some evidence 

 was found of the onshore breeze, known locally as the virazon, another coastal modi- 

 fication of importance. Results show that the survey was undertaken in meteorological 

 conditions which may be regarded as normal. 



NORTHERLY CURRENT 



Though irregular in its distribution, surface current was found to have a more 

 northerly course close to the coast than in the open sea (pp. 133, 189 and 190). Like- 

 wise the subtropical convergence was found to curve northward as it approached the 

 coast (see below). 



WESTERLY SET 



Farther from the coast, northerly drift lessened but only in places was westerly set 

 found to be pronounced (p. 190, Fig. 14). Westerly set is inferred to be widespread in 

 the ocean at large by an unfailing appearance of upwelling near the coast, even under 

 very diverse meteorological and hydrological conditions. 



VERTICAL CURRENTS 



Local influences 



An attempt is made to relate these diverse conditions to the volume of upwelling 



which was also found to vary. The effect of local influences is considered, and the onset 



of heavy wind from the appropriate quarter is shown to be responsible for an unusual 



lowering of inshore temperatures (pp. 140, 143, 148-56, 169). 



Subsidence 



Instances of a reversal of such wind and a rise in temperature have led to subsidence. 



Examples at Antofagasta, Callao and the Guanape Islands are given on pp. 143- 5, and 



153-6; while other examples may be found on pp. 169-71. Evidence for the theory is 



examined critically (p. 213). Such subsidence is not supposed peculiar to the hydrology 



of this coast, but may be a principle of wide application. 



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