The general trend of the sea surface isotherms obtained 

 from Operation HIGHJUMP data i*s similar to the trend of 

 those previously obtained from the Discovery Expedition. 

 However, the HIGHJUMP data indicate an over-all southward 

 displacement of the isotherms. This southward displacement 

 is shown in table 5 where the position of the zero-degree C. 

 isotherm on Operation HIGHJUMP (1946-47) is compared 

 to its position as shown in the Discovery Reports. 



Table 5. Comparison of position of the zero-degree Centigrade iso- 

 therm as observed on the Discovery and HIGHJUMP cruises. 





Longitude 



Latitude 

 (Discovery) 



Latitude 

 (HIGHJUMP) 



Difference 

 (miles) 







180° E 



62° S 



67° S 



300 







135° 



62° 



64° 



120 







90° 



59° 



62° 



180 







45° 



61° 



66° 



300 







0° 



68° 



68° 











45° W 



60° 



62° 



120 







90° 



63° 



66° 



180 







135° 



59° 



66° 



420 





: 



The remaining isotherms (-1 to 3 degrees C.) are displaced 

 much the same as the zero-degree C. isotherm in both di- 

 rection and amount. As can be seen from the table there is 

 a large variation in the location of the zero-degree C. iso- 

 therm except at the zero-degree meridian. 



This general southern displacement of isotherms might 

 be explained if, in the year of the HIGHJUMP observations, 

 there was an unusually strong thermohaline circulation toward 

 the south, associated with a weak wind circulation in the 

 antarctic region which did not offset the south-flowing thermo- 

 haline current. Thermohaline circulations are related to the 

 heating in low latitudes and cooling in high latitudes. Thus the 

 greater abundance of ice encountered on HIGHJUMP than in 

 previous years indicated excessive cooling in the region and 

 suggests a stronger thermohaline circulation. 



24 



