OVERVIEW OF REGIONAL PROGRAMS 



Northeast: Shelf Edge Exchange 

 Processes 



Statement of Problem 



Within the Northeast coastal region, there are 

 over 200 fossil fuel and 20 nuclear power plants, 4 li- 

 quified natural gas facilities, 12 large oil refineries, and 

 2 offshore oil lease areas, as well as major facilities for 

 nuclear submarines at Norfolk, Virginia; New London, 

 Connecticut; and Portsmouth, New Hampshire. 

 About 34,000 containers of radioactive wastes (includ- 

 ing the pressure vessel of the nuclear submarine 

 Seawolf reactor) were discarded off the Northeast 

 Coast between 1951 and 1967. In 1963, the nuclear sub- 

 marine Thresher was lost 300 kilometers off Boston. 

 The 1966 collision of the oil tankers Texaco Mas- 

 sachusetts and Alva Cape led to their explosion in New 

 York Harbor; the Argo Merchant broke up on Nan- 

 tucket Shoals in 1976. This history clearly shows that 

 significant planned and unplanned events will con- 

 tinue to occur here. A strong, continuing research 

 provides the knowledge needed to cope with these 

 events and mitigate their impacts. 



Program Description 



The first phase of the Shelf Edge Exchange 

 Processes (SEEP-I) field program began in 1983-84, 

 when a multidisciplinary team of physical, geochemi- 

 cal, and biological oceanographers set out to test the 

 theory that significant export of biogenic and mineral 

 particles from the shelf occurs, with a subsequent 

 series of geochemical reactions taking place in an or- 

 ganic depocenter on the shelf slope. The first transect 



to test this theory was located at the north end of the 

 Mid-Atlantic Bight running south from Martha's 

 Vineyard. 



The field analysis showed that while there was 

 export of particles from the shelf, it was not nearly as 

 much as postulated. Further, no significant 

 depocenter was found. Data suggested that some of 

 the particles produced on the shelf were consumed 

 there. It was theorized, however, that since the shelf 

 also narrows southward, more water — and therefore 

 more particles — should be exported off the shelf as 

 one proceeded southward along the shelf. The maxi- 

 mum export of particles and water should occur near 

 Cape Hatteras, where it would become entrained into 

 the Gulf Stream and swept far into the North Atlantic 

 (figure 2). 



SEEP-II, initiated in February 1988, focuses on 

 shelf exchange of particles at the latitude of Delaware 

 and Maryland. This phase will determine if the ab- 

 solute flux of particles across the shelf is greater in this 

 geographic region of the Mid-Atlantic Bight than in 

 the northern region. A greater deposition of organic 

 matter on the shelf slope is expected and is being 

 evaluated. Current vectors and planktonic distribu- 

 tions will be determined; subtleties of shelf exchange 

 and biological transformations will be analyzed so as to 

 estimate transport and deposition on the slope. In 

 addition, SEEP-II will evaluate further transport of 

 chemicals from the mid-slope to the interior oceans via 

 redox systems. The field program will operate for 16 

 months through two spring bloom periods. It will 

 describe seasonal and short-term events important in 

 shelf-edge exchange processes for a western boundary 

 circulation regime of the Atlantic Ocean. 



Coastal Ocean Margins Program 



10 



December 1988 



