slight negative gradient in the upper 100 feet, below which 

 nearly isothermal conditions are found to nearly 450 feet. 

 Thus only a small amount of heat has been used to raise the 

 temperature of the surface layers. During January the surface 

 temperature has increased and consequently the negative 

 gradient is stronger. Heating does not extend below 125 feet; 

 however it is sufficiently strong to resist the formation of 

 an isothermal layer. 



Between mid-January and early February, considerable 

 change has taken place. By February the surface has been 

 warmed nearly 1 degree C. and the processes leading to 

 mixing (wind stirring and evaporation) have resulted in a 

 nearly isothermal layer to 200 feet. Below this a negative 

 gradient extends to the cold, winter-cooled layer at 400 feet. 



The changes in the thermal structure below 200 feet may 

 be related to rising of the antarctic circumpolar water nearer 

 the surface, thus bringing the transition layer of positive 

 gradient between 400 and 7 00 feet, as shown in the average 

 curve for February. 



SEA SURFACE TEMPERATURES 



General. Sea surface temperature observations were 

 available in sufficient number to construct isotherms com- 

 pletely around the Antarctic Continent. However, it was 

 necessary to make interpolations in some regions. Surface 

 temperature data analyzed in this report comprise obser- 

 vations made by all three task groups on Operation HIGHJUMP. 

 Although a few of the temperatures were obtained as far 

 south as 78°52'S , by far the greater number of the obser- 

 vations were taken between 60°S and 70°S. Observations 

 extended over the period from December to March. The 

 majority of the observations, however, were made during the 

 months of January and February (see table 4). 



Table 4. Monthly distribution of sea surface temperature observations. 1 





Month Number of Observations 



Per Cent of Total 







December 1946 434 

 January 1947 815 

 February 1947 499 

 March 1947 128 



23 

 43 

 27 



7 





22 



