SECKEL and YONG: SEA-SURFACE TEMPERATURES AND SALINITIES 



35 50 



35 25 



35.00 



34 75 



34 50 



3525 



35.00 



34 75 



>- 



t 3450 



z 



-0 50 



0.25 



0.00 



-0.25 



FIGURE 2.— Koko Head salinity, 1956-73: A. Fitted curve with a 3-mo resolution (n = 1-72). B. Long-term variation <n = 1-17). 

 C. Short-term variation (n = 18-72). D. Residual variation in = 19-35, 37-53, 55-71). 



curves are shown in panels B of Figures 1, 2, 

 and 3. 



In the Koko Head temperature little variation 

 due to the longer period harmonics is apparent 

 until 1960 when perturbations of 0.5° to 1°C 

 began. A rising temperature trend between 1966 

 and 1968 was followed by a decline to a pre-1960 

 temperature level. Both the Koko Head salinity 

 and Christmas Island temperatures show the 

 large perturbations previously noted. At Koko 

 Head a pronounced salinity decline began in 1966, 

 reaching almost 34.5%o in 1968 before rising 

 again to a range near 35%o. Times of high Christ- 



mas Island temperatures stand out. A prominent 

 feature is the pronounced temperature decline 

 during 1973 from one of the highest values to the 

 coldest temperatures observed during the 20 yr 

 of our record. 



Short-Term Changes 



The short-term changes relative to the long- 

 term trends are another scale of interest that can 

 be obtained by subtracting the moving average 

 or the long-term values of the previous section 

 from the monthly observations. In our case, and 



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