76 



OBSERVED NEAR-SURFACE 



MEAN AND LOW-FREQUENCY FLOW 



(DECEMBER 1989 - SEPTEMBER 1991) 



42 6 - 



4? . - 



42 4 



42 3 - 



422 



42 1 - 



42 



41 9 



All Data 

 4-8 m 



-71 



•70 8 



-706 -704 



Longitude 



-70.2 



-70.0 



Figure 3. Map showing the mean flow (solid arrows) and the daily variability (shown as 

 ellipses centered around the tip of the mean flow) for all near-surface (4-8 m depth) current 

 measurements made from December 1989 to September 1991. Typically, the daily-averaged 

 current originates at the station symbol and flows toward any location within the ellipse. The 

 arrows and ellipses have been scaled to correspond to the distance a particle moving with that 

 current would travel in one day. The mean-flow pattern suggests weak flow into 

 Massachusetts Bay from the north and across Stellwagen Bank, southeastward along-shore 

 flow near Scituate and Plymouth, easterly flow in Cape Cod Bay, and outflow in the channel 

 north of Race Point (bold arrows). The area of the new ocean outfall is an area of weak 

 flow compared to the outer bay and there is no strong preferred direction of flow; it is 

 apparently located to the west of the stronger residual coastal current system. This means 

 that water and material here are mixed and transported by a variety of processes rather than 

 being swept in a consistent direction by well-defined steady currents. Station BB is the 

 USGS long-term monitoring station. From Geyer et al (1992). 



