In the fine-grain sediments southwest of Nantucket I., values 

 of 6.0-10 mg/g organic carbon and 0.8-1.2 mg/g nitrogen were 

 recorded (New England OCS"). Highest concentrations 

 (15,000 fjg/1) of seston were measured on the shelf south of 

 Nantucket Shoals during the winter (Milliman et al. footnote 

 5;Aaronetal. 1980). 



Physical Oceanography 



Circulation. — The major pattern of circulation on Georges 

 Bank was described earlier by Bigelow (1927) and Bumpus 

 (1973, 1976) and has been updated by Butman et al. (1980). 

 The data of Butman et al. showed a clockwise circulation pat- 

 tern around the Bank. Flow on the southern flank was con- 

 sistently toward the southwest. West of the Great South Chan- 

 nel and south of Nantucket I., mean flow was measured to the 

 west-northwest along contours of local bathymetry (Dorkins 

 1980). 



On the eastern side of Great South Channel, mean flow was 

 consistently toward the north at 5-10 cm/s at all depths (But- 

 man et al. 1980). At a station just south of Great South Chan- 

 nel, there was a westerly flow similar to that along the southern 



1J New England OCS Environmental Benchmark. 1978. Draft final report, Vol. 

 V, Sects. G-J. Energy Resources Co., Cambridge, Mass., 224 p. 



flank. On the western side of Great South Channel, little net 

 flow was measured. 



Great South Channel has been historically considered a ma- 

 jor exit for Gulf of Maine waters (Schlitz in press). However, 

 recent water current measurements indicate that mean (low 

 w ithin the channel is directed mainly toward the Gulf of Maine 

 (Butman et al. 1980). Schlitz et al. (1977) showed that a perma- 

 nent front exists across the channel from Nantucket Shoals 

 toward Georges Bank, separating the Gulf of Maine from the 

 shelf to the south. According to Schlitz (in press), a small 

 amount of water flows southward through Nantucket Shoals, 

 but this probably does not contribute a significant volume. 



Bottom temperature. — When the study was conducted in 

 June 1962, a cell of cold bottom water (6.1 °-6.9°C) extended 

 in an east-west band from the New York Bight eastward to 

 long. 69°30'W (Fig. 3). This cell occurred at depths of 40-80 

 m, roughly the mid-shelf region. The cold cell was bounded on 

 the north by higher coastal water temperatures (< 12°C) and 

 on the south by values of 10-12°C near the shelf break. Long- 

 term (1940-66) annual maximum and minimum bottom-water 

 temperatures near the shelf break were 16°-17°C and 1 C -2°C, 

 respectively (Colton and Stoddard 1973). However, the annual 

 range here is normally 2 C C. Offshore shelf waters, particularly 

 in shallow portions, may range from 3°C in February-March 

 to 14°C in September-November (Wigley and Stinton 1973). 



Figure 3. — Bottom temperature ('C) off Martha's 

 Vineyard, Mass., from measurements taken at sta- 

 tions (o), June 1962. 



