The accumulation of river water between Cape Cod and Chesapeake Bay 



351 



as well as several stations occupied by the Atlantis and by other vessels of the Wdod-; 

 Hole Oceanographic Institution during recent years. 



The volume of water between depth contour lines for the various areas shown in 

 Fig. 1 are listed in Table I. These were computed from the planimetercd surface area 

 and the average depth which was obtained from the U.S. Coast and Geodetic Survey 

 Navigation Chart #1000. All volumes, and the average fraction and accumulation of 

 fresh water, are computed for the entire depth of the water column, the contour lines 

 being the inshore and offshore limits of the area considered. 



The average fraction of fresh water was computed from the graded depth mean 

 of the salinity values for each station. The bottom bottle of each cast was used to 

 characterize the water from that depth to the recorded or chart depth of the station. 

 This results in an underestimate of the deep salinities, but the volume of river water 

 calculated for the depths below the bottom bottle rarely exceeded 10 "„ of the total 

 river water, even for the summer observations when stratification was greatest and 

 the error would be most pronounced. 



(n4 



SPRING 



1000- 



SUMMER 



-100- 



-1000— 



WINTER 



-1000- 



33 



D' 



Fip 7 The deoth mean salinity and proportion of fresh water for various areas indicated in Fig. 1. 

 The numl^rsoTeaSrtrne indicate the depth, in fathoms, of the outer boundary of the subd.v.s.on 



considered. 



Soring- 328 stations occupied during April, May and June; 



Summer- 203 stations occupied during July, August and September; 



Winter: 325 stations occupied dunng October-March inc. 



The average fraction of fresh water and the corresponding salinity for each sub- 

 area of Fig 1 are given in Fig. 2 for the three periods of year. The nver water found 

 in the spnng period decreases from a mean value of 7-02 ».. for the i""-"^^-; P^;';;" 

 (shore-20 fathoms) to a mean value of 0-33% over the continental slope (100 1000 

 fathoms). The values also decrease from north to south. Th.s would ,iot appear 

 obviously from the salinity charts of B.CHt.ow and Shaks (1935) wh.ch s ow lower 

 surface salinities to the south. However, they also show max.mum vert.cal grad.ents 

 of salinity m this area, and the average salinity over the enttre w.ter co umn ,s gru tcr^ 

 The decreasing fresh water fraction to the south is observed tor all ol the depth 

 Ganges to the 100 fathom contour. Between the 100 and 1000 fathom contours the 

 fresh water fraction decreases somewhat toward the north. 



