3-31 



By February, temperatures in the outer harbor and adjacent 

 waters of Long Island Sound were as low as -0.5 C. Waters of the inner 

 harbor were slightly wanner (up to 1.0 C) . The surface temj)orature maps 

 show that warmer inner harbor waters tended to occupy the western side 

 of the harbor whereas the eastern side was dominated by the colder Long 

 Island Sound waters. 



March cross-sectional data show the cold isothermal conditions 

 of Long Island Sound at the harbor mouth (Station 20) (average temp- 

 erature was 3.0 to 3.5 C) . Within the inner harbor, a warmed near- 

 surface layer about 1 m thick of up to 6.5 C was clearly evident. Near 

 the head of the estuary on the ebbing tide, warm, low-salinity waters 

 from upland drainage were flushed into the main harbor near Station 3 

 and formed this surface layer. On the flooding tide, this warmed water 

 became trapped on the western side of the harbor and colder, more saline 

 waters intruded landward into the upper estuary. By April, seasonal 

 warming of Long Island Sound waters was well established, with average 

 temperatures of 8.0 to 9.0 C. Ebb-tidal temperatures were up to 14.5 C 

 at Station 1 and the stratified layer across the inner harbor was almost 

 2 m thick. The pattern for May remained about the same except that 

 temperatures had increased by a few degrees (to 10.5 to 11.5 C) at the 

 harbor mouth and up to 16.0 C in the Quinnipiac (Station 1) . On the 

 flood tide, the warmed inner harbor waters from the preceding ebb tide 

 moved toward the western half of the harbor. 



In June, Long Island Sound waters developed strong thermal 

 stratification, averaging 17.5 C near the surface and 14.0 C near the 

 bottom (Figure 3-5) . Across the inner harbor, temperatures were higher, 

 but vertical gradients were less distinct due to greater mixing and a 

 weak halocline. In July, the Sound showed a fairly thick, warm near- 

 surface layer (21.0 to 22.7 C) and cool near-bottom waters (19.0 to 20.0 C) 

 Land runoff on the ebbing tide was up to 26.0 C, but the isotherms 

 indicated weaker stratification and more vertical mixing across most of 

 the harbor. 



