202 MARIOX EXPEDITION TO DAVIS STEAIT AXD BAFFIN" BAY 



sides and near the bottom. If the current map of May, 1922. be 

 compared with others constructed in 1926 and 1927 (see Smith. 1927 

 and 1927b), we find it representative of normal conditions during 

 spring Avhen the Labrador current is believed to be most voluminous. 

 The opposite extreme, when there is only a weak flow of the cold 

 current south of Newfoundland is represented by observations of the 

 ice patrol made October 21-26, 1923 (see Smith, 1924. pp. 151-164) : 

 February. 1922 (see Smith, 1923, p. 94) ; and even June 9-25. 1927 

 (see Smith, 1927b, pp. 87-93). At such times it is estimated that 

 the discharge past the Tail of the Bank may fall to 10 cubic miles 

 or so per day (0.8 million tons per second). As pointed out on 

 page 156, the flow and volume of the Labrador current shows wide 

 fluctuations. The current may not only show a seasonal variation 

 within the year, but at the same time alter irregularly in velocity 

 and size over periods of a month or even less. With maximum and 

 minimum rates, in terms of daily volume of about 70 and 10 cubic 

 miles, respectively, a value of 40 cubic miles (3.2 million tons per 

 second) may be assumed to be approximately the year round mean. 

 According to this figure the total yearly "discharge is, therefore, 

 something like 14,600 cubic miles. 



The mean temperature of the cold current in cross section, which 

 we have calculated above, is 37° F., and it discharges south of Xew- 

 foundland into the North Atlantic at latitude 43°. The normal 

 surface temperature for the latitude at which the Labrador current 

 discharges and mixes with the ocean masses off the Tail of the 

 Grand Bank is approximately 54° F.^^' The drop in temperature 

 from the surface to a depth of 600 meters (the thickness of the 

 circulatory layers) is about 9° F. The mean annual temperature of 

 this 600-meter ocean layer is therefore approximately 47° F. This 

 value not only includes the chilling effect of the Labrador current in 

 the vicinity of the forty-ninth meridian but it also takes into con- 

 sideration the warming effect of the Gulf Stream farther eastward 

 in the same latitude and therefore the two effects are more or less 

 counterbalanced in the temperature value of 47° F. Assuming the 

 average temperature of the Labrador current is 37° F., the mean 

 annual cooling effect of this discharge off the Tail of the Grand 

 Bank is therefore 10° F. Consideration of the melting ice volume 

 of 467 cubic miles and annual volume of Labrador current discharge 

 of 14,600 cubic miles indicates that the cooling effect of the latter 

 would counteract an amount of ice about four times as great as 

 normally is melted in the northwestern North Atlantic; or to put 

 it another way, the branch of the Lahrador current which dis- 

 charges at the Tail of the Grand Bank has four times the cooling 

 effect as that of the amvual melting of Arctic ice for the loestern 

 North Atlantic. 



The Marion expedition measured a section across the continental 

 shelf opposite Hamilton Inlet and from a jjreliminary calculation of 

 these data the cubical daily transport of the main trunk of the 

 Labrador current is approximately 130 cubic miles (10.5 million 

 tons per second). If we assume, therefore, that the branch of the 

 Labrador current that passes the Tail of the Grand Bank amounts 



»•■' Kriim'mel (1907, p. 400) has calculated tlie mean annual surface of ocean water for 

 both north and south latitudes. At 43° north latitude it is 12° C. (53.0° F.). 



