Paper 11 



EFFECTS ON ESTUARINE AND COASTAL WATERS 



Increased vertical mixing: The increased density of chilled 

 water v. i I L accelerate vertical mixing and alter normal 

 circulation patterns in inshore waters. 



Ice covgr: oecause the onset of ice cover causes abrupt 

 cessation of uina driven vertical tiixingx the salinity in some 

 estuaries may be above normal near bottom and below normal near 

 the surface. 



^icreased rung,ff : Decreased coastal runoff resulting from frozen 

 streams and snowfalls instead of rainr results in general 

 elevation of estuarine salinities^ although the opposite effect 

 can be looked for in the upper oarts of mixed estuaries where the 

 penetration of saline water along the bottom is driven by surface 

 flow toward the ocean. 



ice cover effects in CQastaJL zane: Ice cover and near freezing 

 temperatures in estuaries and lagoons along the southeast 

 Atlantic coasts where such conditions are a rarity^ may severely 

 affect some resident marine species. Along the northeast coast 

 su-ch conditioDSr although normal in the winter/^ may be having 

 marked effects on the marine life because of their unusual 

 duration/' offshore extension/ and depth penetration. 



Strong seriQii runoff: Wherever there are above normal 

 accumulations of snow and ice in the drainage basins^ the 

 possibility exists of strong spring runoff. In the estuaries^ 

 this would result in an abrupt reversal of the salinity and 

 circulation conditions that now prevail. On the inner 

 continental shelf^ strong runoff could lead to early 

 stratification of the water column with the possibility of anoxia 

 developing next summer^ as occurred last summer off New Jersey. 

 Despite the accumulation of snow and ice in the drainage, basins/' 

 however* strong runoff will sti I L^ depend on the volume of 

 precipitation during the spring and -timing of the thaw. 



I!}§if yaie£ tenjQer atures : Not only should water temperatures be 

 expected to equal or go below record low values* but the normal 

 spring and summer warming cycle may be delayed. Persistence of 

 the cold water can be expected* particularly in bottom waters 

 over the outer continental shelf* where the cold water becomes 

 insulated from seasonal warming by formation of a warm surface 

 layer. The vertical stratification may also be stronger than 

 usual because of cold dense water persisting at the bottom. 



The Atlantic Environmental Group* NMFS* is attempting to 

 determine whether the warm Slope Water that contacts bottom on 

 the outer continental shelf in the Middle Atlantic Bight could be 

 displaced in 1977 by abnoririally chilled Shelf Water. Such 



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