based on ship weather reports, have been in- 

 dividually compared with the long-tern-i aver- 

 age monthly charts to provide n-iore infor- 

 mation about the period 1957-59. Most! -degree 

 rectangles with data showed positive anomalies 

 of about 2° to 6° F. from July 1957 through 

 July 1959, but the anomalies were less con- 

 sistent in the first half of 1957 and the last 

 half of 1959. Central American temperatures 

 were normal in most months after July 1959. 

 In most months of 1960, temperatures were 

 normal over the whole region. 



Even during the warm period the anomalies 

 were smaller in the Central American region 

 than in the Mexican region. The observation 

 of Austin (1960), that Equatorial Counter- 

 current waters showed a smaller anomaly 

 than adjacent waters during 1955, may be 

 enlarged into a hypothesis that the Counter- 

 current exercises a moderating influence on 

 anomalous temperature regimes in general, 

 both low and high, in the region between 5° 

 and 10° N. where it approaches the coast. 



Figure 5 shows also the rise in surface 

 temperatures along the Baja California coast 

 from 1955 to 1959, which is discussed else- 

 where in the paper under "Tuna ecology." 



Surface Temperature Anomalies and 

 Associated Observations in Peruvian 



Waters (W. S. Wooster) 



During the period 1939-56, ocean surface 

 temperatures measured by Peruvian vessels 

 were collected and published by the Compania 

 Administradora del Guano in a series known 

 as Mapas Mensuales. From these data were 

 selected the 1-degree squares for eachdegree 

 of latitude from 4° to 17° S., for which data 

 were most abundant. These were summarized 

 in a long-term {18 years) average picture of 

 the monthly change of surface temperature 

 along the Peruvian coast. This showed the 

 annual range of surface temperature varying 

 from about 4° C. at 12° S. to nearly 6° C. at 

 4° S. Highest temperatures (up to more than 

 22 C.) occur farthest north in the summer 

 and lowest temperatures (less than 15° C.) 

 during winter at 1 3 to 15° S. 



Detailed yearly charts were also prepared, 

 which showed the character of year-to-year 

 differences. During El Nino years, such as 

 1941, the summer warming showed a marked 

 increase in southern penetration, duration, 

 and intensity. During cold years, such as 

 1950-51, summer warming was notably re- 

 duced, and the winter cold regime more 

 extensively developed than usual. Examination 

 of these charts led to speculation about the 

 cause of El Nirio, discussed in the next 

 section. 



Since 1957 an active program of marine 

 research has been carried out by the Peruvian 

 Consejo de Investigaciones Hidrobiologicas. 

 In part this progrann has consisted of periodic 

 cruises off the Peruvian coast, from 4° to 17° 

 S. and offshore a distance of 60 miles. Hydro- 

 graphic observations included bathythermo- 

 graph lowerings and surface salinity measure - 

 ments. Data from three cruises in 1958 (Feb- 

 ruary, April, and September) have been sent 

 to Scripps Institution for analysis. These have 

 been used in the preparation of temperature 

 profiles and in an exannination of the tempera- 

 ture -salinity relationship of surface waters. 



The great value of these data is that they 

 constitute an occasional three-dimensional 

 check on the oceanic significance of coastal 

 temperature being continuously monitored at 

 Puerto Chicama and elsewhere. For instance, 

 the cruise of February 1958 showed two in- 

 trusions of warm water from the ocean on to 

 the Peru coast, separated by an area of cooler 

 water; the salinity of the northern warm 

 tongue of water was lower than that of the 

 southern, which suggests a different origin 

 for each tongue. 



The temperature charts have been used as 

 the basis of a paper entitled "Yearly changes 

 in the Peru Current," which is in press in 

 Limnology and Oceanography. 



The work was supported in part (about 50 

 percent) by the Office of Naval Research, 

 and assisted, as indicated above, by the 

 Consejo de Investigaciones Hidrobiologicas. 



El Niiio (TV. S. Wooster) 



One of the most celebrated of oceanic 

 disturbances is that known as El Nino, an 

 occurrence of the first half of the year which 

 is observed at irregular intervals (1891, 1925, 

 1941, 1953, 1957-58) from the coast of northern 

 Peru. Symptoms of this phenomenon commonly 

 reported include the presence of unusually high 

 sea surface temperatures, southward coastal 

 current, heavy rainfall, red tide (aguaje), 

 invasion by tropical nekton, and mass mortality 

 of marine organisms. Conditions during early 

 1958 are referred to above; off central Peru 

 a shallow layer (less than 30 m.) of warm 

 water (over 25° C.) of high salinity (greater 

 than 35.2/00), underlain by a strong thermocline, 

 lay offshore a distance of 20 to 60 miles, and 

 only in a few places was evidence of upwelling 

 present. 



A hypothesis of El Nino has been developed, 

 in which the phenomenon is defined as the set 

 of conditions developing off an upwelling coast 

 when reduction of the wind stress causing up- 

 welling during an extended period of time 

 leads to weakening or cessation of vertical 



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