NOAA PROFESSIONAL PAPER 11 



During May and June strong sea-level pressure rises 

 were observed over the Atlantic Ocean (Dickson 1976b; 

 Taubensee 1976b), which resulted in an increase in the 

 speed and persistence of southerly winds over the Bight. 



Atmospheric forcing is one of the dominant influences 

 driving the New York Bight circulation and exchange 

 processes (Mooers et al. 1976) and thus affects the marine 

 ecosystem. Long-term changes in atmospheric circulation 

 patterns can have a pronounced effect on the strength and 

 persistence of this forcing. Dickson and Namias (1976) 

 demonstrated how different circulation regimes affect the 

 baroclinicity or cyclogenetic potential along the U.S. east 

 coast, reducing or increasing the number and vigor of 

 disturbances. To provide some measure of the relative 

 strength of this forcing during the few months preceding 

 the onset of the 1976 anoxia, the number of storm centers 

 entering the Bight area bounded by 38°- 42° N and 

 70°-75° W was tabulated for February through June, 

 1950-76 (fig. 3-1), based on extratropical cyclone track 

 charts (NOAA 1950-76). Minimum storm activity oc- 

 curred in 1976. Although the average number of storms 

 crossing this area during the 5 months is about 15. only 

 6 storms were recorded in 1976, and only a single storm 

 was recorded in each of the months of February and 

 March. 



The magnitude and persistence of these anomalous 

 weather patterns during the few months preceding the 

 period of bottom-water anoxia suggested a possible con- 

 nection to the observed disruption of the marine environ- 

 ment in the Bight. Sea-surface temperature is considered 

 a relatively good indicator of the degree of stratification, 

 however, with regard to its early onset, other factors may 



1950 51 52 53 54 55 56 57 58 59 60 61 62 63 



FIGURE 3-1. — Number of extratropical cyclones entering New York 

 Bight area (38°-42° N, TC-TS" W). Februarv-June 1950-76. (NOAA 

 1950-76 data.) 



be important in determining the vertical density profile. 

 For example, the temperature of the bottom layers, which 

 are influenced by antecedent winter conditions, affects the 

 surface of bottom temperature contrast. Another impor- 

 tant element is the salinity of the surface waters. During 

 the spring of 1976, low surface salinity contributed to early 

 stratification. 



The surface wind field provides a measure of the large- 

 scale circulation in the Bight. Anomalous winds, by mod- 

 ifying the normal circulation and exchange (vertical mix- 

 ing) processes of Bight waters, could have aided in the 

 development and maintenance of oxygen depletion. Be- 

 cause surface wind stress represents a primary driving 

 force for oceanic motions, intensified or persistent up- 

 welling/onwelling in the Bight could have been an impor- 

 tant factor in the development of a phytoplankton bloom 

 along the New Jersey coast. 



SEA-SURFACE TEMPERATURE 



Sea-surface temperature data were extracted from three 

 principal digital files at the National Climatic Center 

 (NCC): the New York Bight Atlas file (1949-73); the Tape 

 Data Family-11 (TDF-11) file, 1870-1973; and the Global 

 Weather Central Telecommunications file (1973-76). In 

 addition, the National Weather Service's monthly publi- 

 cation, Gulfstream, which contains monthly means of sea- 

 surface temperature by 1° squares, was used for the period 

 1971-76 whenever the number of sea-surface temperature 

 observations exceeded those in NCC files. 



Sea-surface temperatures were analyzed for a 2°-square 

 area (39°-4r N, 72°-74° W) comprising most of the New 

 York Bight region (fig. 3-2). This is the area used by 

 Lettau et al. (1976) for the MESA New York Bight Atlas 

 Monograph 7 on "Marine Climatology," and for which 

 the tape data file covering the years 1949 to 1973 was 

 created. To determine whether surface waters throughout 

 the Bight were unusually warm during the 1976 months 

 preceding the oxygen-depletion event, sea-surface tem- 

 perature means for the months of February, March, and 

 April — for the long-term records of 1876-1976 in the 

 northwest marine area and 1896-1976 in the southwest 

 marine area — were plotted as departures from the 1949-73 

 reference period mean (fig. 3-3). The northwest and 

 southwest T-square marine areas of figure 3-2 include the 

 greater portion of the zone of oxygen deficiency identified 

 in chapter 1. 



A value was plotted only when four or more observa- 

 tions were available for a given year/month. Values de- 

 rived from fewer than 20 observations, which also fell 

 beyond ± 3 standard deviations from the reference mean, 

 were rejected. These limits were arbitrarily chosen to pre- 

 vent undue biases either from too little data or from the 



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