INTRODUCTION 



The summaries of sea water temperatures and densities presented 

 in this publication are based on observations made at locations along 

 the Pacific coast of North and South America and Pacific Ocean islands 

 through the year 196I_|_. The sea water temperatures and densities were 

 observed primarily at tide stations which, in the United States and 

 possessions, were maintained by the Coast and Geodetic Survey, often 

 with the cooperation of other organizations. The data for six places 

 on the California coast, namely La Jolla, Balboa, Port Hueneme , Pacific 

 Grove, Southeast Farallon Island and Blunts Reef Lightship were supplied 

 by the Scripps Institution of Oceanography. The data for places in Chile 

 were supplied /by the Departamento de Navegacion e Hidrografia, Republica 

 de Chile. Other observations in Latin America were obtained through 

 cooperation with the Inter American Geodetic Survey. Data for the 

 Philippine Islands were supplied by the Bureau of Coast and Geodetic 

 Survey of the Republic of the Philippines. For places in other countries 

 the Coast and Geodetic Survey derived the data from observations made by 

 organizations in the particular country. 



Table 1 presents monthly means and annual means and extremes of the 

 surface water temperatures and densities for each year of observation 

 after 1959. Earlier observations, with the exception of certain nine- 

 teenth century data, are combined in five-year groups. For each station 

 at which the series- of observations covered two or more years, the follow- 

 ing monthly values are presented: the mean of the monthly means, the max- 

 imum observed, the mean of the monthly maxima, the mean of the monthly 

 minima and the minimum observed. 



¥hen an asterisk appears in either extreme temperature column in 

 Table 1, it indicates that the extreme may have been exceeded if observa- 

 tions had been available for all months in which the maximum or minimum 

 normally occurs. If observations are not available for any month in 

 which the yearly maximum or minimum may have occurred, the extreme has 

 been omitted. For densities, the yearly extremes are from the months of 

 the year for which means are given. If they are from an incomplete year, 

 they are followed by an asterisk. 



The temperature data given in degrees Celsius are based on thermom- 

 eter readings made in a sample of water drawn by bucket from a foot or 

 two below the surface. They can be converted to degrees Fahrenheit by 

 means of Table 2. 



The density of any substance is defined as the mass per unit volume. 

 The density of sea water, as observed, depends not only upon the amount 

 of soluble matter 'held in solution but also upon the temperature of the 

 water at the time the reading was made. It is necessary, therefore, to 

 reduce the observed densities to some standard temperature in order that 

 they may be comparable. In -this publication the observed densities have 

 been reduced to a standard temperature of 15°C (59°F). The density of 

 pure water at a temperature of 15°C is taken as 0.9991. The density 

 values obtained by using a hydrometer were reduced to the standard temp- 

 erature by using the tables given in C&GS Special Publication No. 298. 



Densities in Table 1 are expressed in terms of the Greek letter sig- 

 ma with a subscript that refers to temperature and is called a sigma-t 

 ( <r^ ) value. Thus: "is ~ ( ''u -1)1000 where ^ is the density of sea 

 water at 15°C (59°F) referred to pure water at [|°C (39.2°F) as unity. 

 For example: If sea water has a density at 15°C of 1.0268, Ojj = 26.8. 

 The actual density of the water may vary from a little less than unity 

 for fresh water at a temperature other than [|.°C to approximately 1.0L|.10 

 for the heaviest sea water. 



The salinity of sea water, denoted by the symbol °/oo, is defined 

 as the number of grams of salts contained in 1000 grams of sea water. 



