JOHNSON and McLAIN: TELECONNECTIONS BETWEEN OCEANS 



The relation between Q-p and sea-surface 

 temperature change in the winters of 1948-67 in 

 the northern Gulf of Mexico is significant (Figure 

 4). Particularly noteworthy is the large net heat 

 loss in the winter 1957-58 accompanied by the 

 large sea-surface temperature change. The 

 decrease in Q/ reaching the sea surface accounted 

 for about 11% of the anomalous heat loss and 

 increased Q^ about 12%. Q^. and Qf^, however, 

 clearly stand out as significantly more important 

 than the other heat budget elements in contribut- 

 ing to the large net loss of heat. Q^; contributed 

 57% of the anomalous heat loss and Q//, 20%. 



Data are not available that indicate the depth to 

 which the sea temperature anomaly extended. One 

 might speculate that it should extend throughout 

 the mixed layer which on the average in the area 

 of study is about 80 m in winter (Robinson 1973). 

 For the three months December 1957-February 

 1958, the anomalous heat loss in the Gulf of Mexico 

 in the area of lat. 25° to 30°N, long. 80° to 90°W 

 was approximately 19,000 cal/cm-. This should 

 reflect an anomalous change in water temperature 

 of about -2.4°C throughout the mixed layer which 

 is very close to the anomalous -2.0°C change ob- 

 served at the surface. 



Though the immediate cause of the development 

 of the cold anomaly appears to have been the flow 

 of cold continental air over the Gulf and western 

 Atlantic, the more general cause may have been 

 due to large-scale interactions over the North 

 Pacific Ocean. A large positive sea temperature 

 anomaly appeared in the eastern Pacific in late 

 1957 and persisted throughout 1958 (Sette and 

 Isaacs 1960) (Eber 1971). Namias (1959) explains 

 that the contrast of anomalous warm ocean 

 temperatures to the east of cold ocean tempera- 

 tures, which was the situation in 1957 in the east- 

 em Pacific, provided abnormal feedback in heat 

 exchange processes to the atmosphere which 

 provided the additional baroclinicity upon which 

 cyclones could feed. This cyclogenesis helped 

 maintain the deep Pacific trough south of Kodiak 

 Island which was abnormally intense by the late 

 fall of 1957. Downstream from this area of ac- 

 tivity, a responsive ridge developed in the western 

 United States (evident from Figure 1) and a deep 

 trough along the Atlantic seaboard. This distribu- 

 tion is also consistent with the statistical findings 

 of O'Connor (1969) who noted that when an 

 anomalously deep trough forms in the 700-mb cir- 

 culation in the east central Pacific, the chances for 

 a trough off the eastern seaboard are high. 



Air-Sea Interactions in 

 Other Years 



It is tempting to argue that events such as the 

 1957-58 occurrence described above occur so sel- 

 dom that it is not worth the effort to study them 

 and their effects on fisheries. Study of years when 

 extreme conditions prevail, however, provides 

 hints of the processes that are occurring in the 

 natural system in other years. Definitive findings 

 through study of more normal years are often 

 diflficult to obtain because processes involved may 

 be obscured by the subtle interactions of a number 

 of factors. 



The interaction of the type described above may 

 not be as infrequent as one might believe. A sit- 

 uation similar to the winter of 1957-58 seems to 

 have occurred in the winter of 1939-40. O'Connor 

 (1958) noted very cold air temperatures along the 

 eastern seaboard in the winter of 1939-40 which 

 were as intense as those in 1957-58. Although sea 

 temperature records are sparse for winter months 

 (December through February) of 1939-40, what 

 data are available show an extremely cold and 

 widespread anomaly in the Gulf of Mexico (Figure 

 5) and along the eastern seaboard where 

 temperature anomalies of 5° and 6°C below nor- 

 mal were observed in February 1940. 



Further analysis of these large-scale air-sea 

 interactions suggest a possible relation between 

 equatorial Pacific Ocean temperatures and those 

 in the Gulf of Mexico. Bjerknes (1969) has shown 

 that in the winters 1957-58, 1963-64, and 1965-66 

 high sea-surface temperatures prevailed in the 

 eastern tropical Pacific Ocean. This is characteris- 

 tic of El Nino years which are best known for the 

 invasion of warm water off the Peruvian coast and 

 effects on the anchoveta populations there. It is 

 known also that in the winter of 1939-40 a severe 

 El Nino was present in the eastern Pacific. In all of 

 these winters cold sea-surface temperature 

 anomalies prevailed in the Gulf of Mexico (Figure 

 5). There appears, then, to be a relation between 

 sea temperature anomalies in the equatorial 

 Pacific and anomalies in the Gulf of Mexico, that 

 is, negative sea-surface temperature anomalies in 

 the Gulf and western Atlantic in some situations 

 may be related to positive sea temperature 

 anomalies in the eastern equatorial Pacific 

 through processes described by various authors 

 mentioned previously and those described in this 

 paper. 



311 



