I. IWTRODUCinOII 



A . Tempe ratu re Distribution in the Upper Layers of the Morth Atlantic 



Annual temperature cycles occur in most parts of oceans, seas, and 

 lakes. For purposes of this discussion, a surface layer about I50 meters 

 thick is considered. The layer may be isothermal or nearly isothermal 

 during winter. During the remainder of the year it is stratified with a 

 mixed layer at its surface, a seasonal thermocline (rapidly decreasing 

 temperatiare ) below the mixed layer, and moderately decreasing temperature 

 below the thermocline. 



The annual march of temperatiire in the mixed layer at any given 

 location in the ocean has a well-defined pattern and can be approximated 

 without much difficxiLty by the expression: 



^o~^s,a + A,cos (a;t + a,) + Ag cos(2wt +a2) + '" (1) 



where = mean annual surface temperature at the location 



A|,A2--= amplitudes of temperature oscillation for various harmonics 



w = angular frequency equal to ~j— , where T = period length 



of the first harmonic term 



t = time, and 



a,,a2 = phase angles. 



Surface temperature could always be computed by equation (l) if the 

 annual march of temperature depended strictly on predictable factors. How- 

 ever, this is not the case, because nonperiodic factors are always present 

 and actual temperature usually differs from the mean. The departure of 

 actual surface temperature, 6'^ , from 6^ constitutes the surface temper- 

 ature anomaly A6q at a given location at a given time, thus 



Equation (l) is not needed for mean surface temperature computa- 

 tion for most areas in the Morth Atlantic where surface temperature data 

 have been collected for many years, and for which mean monthly surface 

 temperature charts, based on sufficient data, are available. Mean daily 

 temperatures can be interpolated from the mean monthly charts with satis- 

 factory approximation. If equation (l) is applied for computation of mean 

 surface temperature, amplitudes and phase angles should be either based 

 on characteristics of the region of study or determined as fvinctions of 

 latitude. 



The mean annual range of surface temperature in the Atlantic is 



