the warming trend beginning in the 1940s, warmer winter water temperatures 

 accounted for most of the observed rise (Taylor et al. 1957). Warmer winters 

 could affect plant and animal populations by decreasing icing, which causes 

 mortalities in the intertidal zone, and allowing southern species to survive 

 winter . 



Atmospheric temperature variability is the main cause of fluctuations in sea 

 water, but the formation of locally produced dense cold water in winter 

 complicates the relationship. Similar long-term trends were found in the data 

 from St. Andrews, New Brunswick. However, absolute temperatures differ 

 between the two regions. 



Seasonal changes in temperature and salinity . The temperate coastal 

 waters of New England exhibit large seasonal variation in temperature compared 

 to most oceanic waters. The seasonal range of water temperature in region 2 

 (i.e., Boothbay Harbor) is from 28° F (-2 ^C) to about 73 ^F (23 °C). 

 Physiological processes of organisms can be markedly affected over this range. 



Seasonal changes in coastal water off Boothbay Harbor, described below, are 

 based on a time series of data from Apollonio and Applin (1972; appendix A). 

 Although this time series represents the most comprehensive collection of data 

 available, too few stations were sampled to draw more than general conclusions 

 about nearshore temperature distribution. Small-scale temperature 

 variability, due to turbulent mixing induced by currents, and irregular 

 topography in this area make temperature distribution too complex to be 

 deduced from such a limited number of stations. 



As spring approaches, the atmosphere warms the surface waters of the ocean, 

 making them less dense, and a distinct surface layer forms. This layer 

 becomes thicker as warming continues and in Maine coastal waters reaches 100 

 feet (30 m) by August. Its depth is clearly defined by a rapid change in 

 temperature of several degrees in a few meters and a correspondingly rapid 

 increase (downward) in density. The density change lends a great deal of 

 stability to this boundary, which is called a seasonal thermocline or 

 pycnocline. From the time of its initial formation (May in Maine) the 

 thermocline separates the ocean into two layers, each of which mixes 

 relatively freely within itself but has only limited exchange with the other. 



During the fall and winter months, when atmospheric temperatures are lower 

 than sea surface temperatures, waters lose heat to the atmosphere and cool 

 until they become sufficiently dense to sink. Continued cooling results in 

 overturn of the entire water column, which results in water of uniform 

 properties being distributed from surface to bottom or to approximately 300 to 

 500 feet (100 to 150 m) in deep water (late February). 



A number of processes occur that can affect the seasonal cycle described 

 above. They include storms, upwelling , and tidal currents. Seasonal 

 fluctuations in salinity are greatest in areas adjacent to freshwater 

 discharges. Changes in salinity in marine waters near the mouths of estuaries 

 in the characterization area have not been monitored. The extent of influence 

 of this runoff in marine waters is therefore unknown. The Kennebec estuary 

 (region 2) and the Penobscot estuary (region 4) are expected to have the 

 greatest effect on the salinity of adjacent marine waters. 



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