1939-40 



FISHERY BULLETIN: VOL. 73, NO. 2 



1957-58 



lOO 



1963-64 



1965-66 



lOO" 95' 90 85' 80 100 95 90 85 



Figure 5.-Sea-surface temperature anomalies (°C) in the Gulf of Mexico for selected winters. 



80" 



During the recent 1972-73 El Nino, however, a 

 situation occurred where this relation did not 

 exist. A trough did not develop off the eastern 

 seaboard until late winter and was short-lived in 

 nature. During most of the winter it was situated 

 over the central United States. Consequently, the 

 flow of cold, continental air over the Gulf of 

 Mexico, especially in the eastern Gulf, was not as 

 intense as in previous El Nino years, and thus not 

 as much cooling of surface waters occurred in the 

 Gulf of Mexico. 



A situation opposite to the cold winters along 

 the eastern seaboard described above occurred in 

 the winter 1948-49. Very little cooling occurred in 

 the waters of the Gulf, and the net heat exchange 

 atthe air-sea interface likewise was small (Figure 

 4). The sea-surface temperature anomaly patterns 

 in the winter of 1948-49 compared to the winter 

 1957-58 are remarkably opposite in sign and mag- 

 nitude (Figure 6). Whereas, cold sea temperature 

 anomalies prevailed in the latter winter off the 

 southeastern United States, widespread warm 

 anomalies were present in the winter 1948-49. In 

 this winter a distinct ridge developed over the 

 eastern United States in the 700-mb heights, a 



trough over the western U.S., and another ridge in 

 the northeast Pacific (Figure 7) which is consistent 

 with the hypothesis given by Quinn (1972) and by 

 the findings of Namias. 



Namias (1972) suggested that the 1957-58 

 winter marked the beginning of a new climatic 

 regime in the northern hemisphere. He shows, for 

 example, that the winter mean air temperature at 

 Atlanta, Ga. for the decade 1948-57 was about 5°F 

 higher than the following decade. A trend is also 

 noted in decadal differences of sea temperatures 

 in the Gulf of Mexico. The 1948-57 decade average 

 of February sea temperature was about 1.0°C 

 higher than the 1958-67 February average. 

 Somewhat lower sea temperatures generally 

 prevailed along the entire eastern seaboard in the 

 1958-67 decade compared to the one preceding. 



Sea temperatures and circulation off the U.S. 

 west coast also showed a climatic change. Huang 

 (1972) calculated that southward transport in the 

 general area of the California Current from San 

 Diego to long. 150°W in the period 1958-69 was less 

 than in the previous decade. He showed further 

 that the California Current annual sea tempera- 

 tures were as much as 1.4°C above normal in the 



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