CHAPTERS 



Density differences at station 88 (fig. 5-2) were signif- 

 icantly greater during 1976 for March, April, and May, 

 but were slightly less during the summer months. At sta- 

 tion 23 the differences between April and May were sim- 

 ilar in 1974 and 1976, but were considerably greater than 

 for the corresponding time in 1975. At station 69 the strat- 

 ification was more strongly developed in 1976 than 1975 

 until the autumnal breakdown. 



TEMPERATURE 



During the first half of 1976, the monthly mean air 

 temperature had a number of anomalous features. Ac- 

 cording to Diaz (ch. 3), January was somewhat colder 

 than normal, whereas extreme warm air temperatures 

 prevailed during February and March. During April the 

 mean air temperature remained about 1° to 2° C above 

 normal, but the monthly mean temperature masked a 

 large change in April. Record cold weather prevailed dur- 

 ing the first half of April, followed by record warmth in 

 the second half. We can conclude that average air tem- 

 peratures over New York Bight during the first 4 months 

 of 1976 were only slightly above normal — record cold pe- 

 riods partially offset record warm periods. 



Monthly mean sea-surface temperatures for the Bight 

 Apex and Long Island area for 1975 and 1976 were com- 

 pared with historical mean temperatures (fig. 5-3). The 

 monthly mean sea-surface temperatures for February, 

 March, and April 1976 exceeded the long-term mean and, 

 qualitatively at least, correlate with the corresponding 

 mean monthly air temperatures. Monthly sea-surface tem- 

 perature anomalies (departure from 1949-76 mean) for 

 1974, 1975, and 1976 are compared in figure 5-4. They 

 indicate that the mean monthly sea-surface temperatures 

 for the January-April period were 1° to 2° C above normal 

 for all 3 years. During the winters, temperatures decreased 

 until February (fig. 5-3), when the mean monthly tem- 

 perature was minimum. A spring warming trend was re- 

 corded for March. An above-normal sea-surface temper- 

 ature continued through spring and summer during all 3 

 years. In May and June 1975 temperature increases ex- 

 ceeded the more normal conditions as reflected in May 

 and June in 1976. 



Temperature variations with depth were plotted as a 

 time series for station 88 (fig. 5-5). Temperature data 

 from moored current meters (stations LT2 and LT4) sup- 

 plemented the temporal data from cruises. (See chapter 

 7, fig. 7-7.) During March 1975 and 1976 the water was 

 nearly isothermal, varying between 5° and 6° C. The 

 March warming trend did not result in significant thermal 

 structure until mid-April in 1976 and in late April 1975. 

 By mid-April 1976, the mean surface temperature was 

 1.7° C warmer and the mean bottom temperature 1.2° C 



warmer than during the corresponding period in 1975. 

 During May and June this differential continued. The ther- 

 mocline during the summer months remained strong and 

 at a near-constant depth. Surface and bottom tempera- 

 tures in July and August were about the same for the 2 

 years. By September of both years (fig. 5-5) the temper- 

 ature had begun to decrease, with a corresponding gradual 

 deepening of the thermocline. By the first of October 

 1976, the surface temperature was about 3° C higher and 

 the bottom temperature was about 1° C higher than at the 

 corresponding time in 1975. 



From the moored-meter temperature data (fig. 5-5), 

 the bottom temperature minimum for the 1975-76 winter 

 varied between 4° and 5° C and was maintained from Jan- 

 uary 23 to February 21, 1976, at which time the temper- 

 ature began to increase. From about February 26, bottom 

 temperature data were recorded for both 1975 and 1976. 

 From that date until April 10, the bottom temperature 

 was about the same for both years. After April 10, 1976, 

 warming increased at a much greater rate than during the 

 corresponding period of 1975. The moored-meter tem- 

 perature data indicated the record warmth lasted until 

 April 26. 



The temperature difference curves in figure 5-6 were 

 constructed using interpolated values from figure 5-5 and 

 a similar figure for station 69 (not shown). April and May 

 had a slightly greater surface-to-bottom temperature dif- 

 ferential in 1976 than in 1975. In summer 1975 and 1976 

 the temperature differential between surface and bottom 

 waters was greater at station 69 than at station 88. 



SALINITY 



Salinity stratification was very prominent at all stations 

 during April 1976, in contrast to the same period in 1975 

 when stratification was slight. During March, stratification 

 was considerably greater in 1976 than in 1975 at station 

 88 (fig. 5-7). At station 23, however (fig. 5-7), stratifi- 

 cation was quite low during March 1974 and 1976. The 

 greatest contrast between years was in April in the Bight 

 Apex (station 23). There, salinity stratification was sig- 

 nificantly greater during April-May 1974 and 1976 than 

 during the same period in 1975. At station 88 stratification 

 was considerably greater in 1976 during March, April, and 

 May than in 1975. At station 69 during April 1976 strat- 

 ification was greater than April 1975 (fig. 5-7). During 

 March and May, stratification was about the same for the 

 2 years. During the summer, stratification appeared to be 

 greater during 1975 at stations 23 and 88 than in 1976. 



Armstrong (ch. 6) compared monthly discharge rates 

 for the Delaware and Hudson rivers for 1976 with long- 

 term means and extremes. The discharge rate usually 

 reached a maximum in April when it was significantly 



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