the wreck there are strong tidal currents, which at times exceed 2 knots. 

 One measurement indicated approximately 6 knots. These currents are strongly 

 influenced by local topography, and extrapolation may be very difficult if 

 not impossible. Table VII-6 in Appendix VII contains tide predictions from 

 the National Ocean Survey (NOS), NOAA. 



Eulerian water motion measurements were obtained by standard current 

 meter techniques as well as by current probes deployable from the air. In 

 response to the oil spill, six moorings for measuring water currents were 

 implanted. B. Butman, USGS, Massachusetts, implanted four current meter 

 moorings from the tug Whitefoot. Three of these moorings contained one or 

 more self-recording current meters, while the fourth (121) was a tripod 

 mooring that recorded sediment conditions, currents, water depths, light 

 transmission, and bottom photographs every four hours. A current meter 

 mooring was also implanted at the Nantucket Light Ship during Cruise 20 of 

 the Oaeanus on December 28. Before the oil spill on December 5, B. Butman 

 and D. Folger, USGS, had implanted a current meter mooring in the area from 

 the Oaeanus. The Endeavor implanted a current meter mooring supplied by D. 

 Shonting of the Underwater Systems Center (NUSC) on December 29, 1976. An 

 attempt to recover this mooring on February 9, 1977, was unsuccessful because 

 it could not be relocated. Attempts to relocate this mooring are continuing. 

 All these moorings were to be retrieved during February or March 1977, and 

 the data obtained will be available through EDS, NOAA. In the historical 

 past, NOS has measured currents to support tidal table generation in the area 

 where the Argo Merchant foundered. These records are of short duration and 

 are available through EDS. Three sites were covered in 1960 and three others 

 in 1932. Table VII-7 gives the characteristics of all current moorings, and 

 Figure 2-3 shows their locations. 



In response to the spill, single-point measurements were obtained by the 

 SOR Team and by AMSI with Richardson current probes (Photographs 33 and 34, 

 Appendix III) deployed from the air. These current probes operate by releas- 

 ing packets of dye at known time intervals after they are resting on the 

 bottom. The packets rise to the surface whency they are carried by the 

 surface currents. By assuming that they follow the same path from the bottom 

 to the surface (i.e., the vertical current structure is constant), then the 

 separation of the dye packets when they are both on the surface is only a 

 function of the surface current velocity and t;he known time interval between 

 releases. Table 2-1 gives the results of these measurements, most of which 

 were taken in support of oil and oil/water differential velocity studies (see 

 Section 2.2.4). 



Lagrangian water motion measurements were obtained by tracking, as a 

 function of time, USCG datum marker buoys (DMBs) , large sheets of pljrwood, 

 large dye patches, drift cards, sea bed drifters, and a NOAA drifting buoy. 



DMBs are generally used by USCG for search and rescue missions. They 

 are tracked by a radio beacon and have an operational life of 36 hours. 

 Since these buoys do not transmit a unique identifier, there may be confusion 

 if many are deployed in the same region. Five DMBs were deployed, as in- 

 dicated in Table VII-8 in Appendix VII, and tracked. The first was tracked 

 from 1048 on December 18 until 1023 on December 20, showing four positions. 



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