DAVIS STRAIT AND LABRADOR SEA 175 



This gives an excess of heat entering amounting to 1.7 billion kilo- 

 gram calories per second. If the average temperature of the water 

 sinking beloAv the 1,500 meter level is assumed to be 3.2° C, the cor- 

 responding outflov7 of heat was about 6.1 billion kilogram calories 

 per second on the basis of the current balance tabulated on page 

 173. This figure of 6.1 compared with the above excess of current- 

 borne heat entering above 1,500 meters of 1.7 billion kilogram calories 

 per second leaves an excess of departing current-borne heat of 4.4 

 billion kilogram calories per second. It seems reasonable that this 

 represents the order of magnitude of the average summer rate of 

 absorption of insolation for it is estimated ^^ that, during the sum- 

 mertime, the insolation reaching the surface of the sea in this area 

 amounts to about 20 billion kilogi'am calories per second of which 

 perhaps more than 40 percent is lost, as far as the sea is concerned, 

 through reflection. If this figure for reflection is accepted, 12 billion 

 kilogram calories per second remain to account for radiation, evapora- 

 tion, and absorption. As radiation is probably small, approximately 

 two-thirds of the solar heat not reflected from the surface goes 

 for evaporation and only one-third is absorbed. This proportion 

 of absorption is probably too low because no account has been taken 

 of land drainage, compensating sinking, and consequent transport 

 of heat to depths below 1,500 meters. 



CABBELING 



The indicated sinking of approximately 1.9 million cubic meters 

 per second volume of current below the 1,500-meter level and also, 

 proportional quantities of heat, is substantiated by the position of 

 the axis of saltest water along the southwest coast of Greenland 

 for the summer of 1928. These data when plotted against depth 

 (fig. 132) show that the Irminger- Atlantic water sank from the 200- 

 meter level off Cape Farewell to about the 500-meter level off God- 

 thaab. The temperature-salinity curves representative of the West 

 Greenland Current (fig. 23, p. 48), if interpreted in terms of density, 

 also indicate the progressive increase of density along its course. 

 This sinking of the Irminger-Atlantic water is verified by the obser- 

 vations of Baggesgaard-Rasmussen and Jacobsen (1930) and those of 

 Riis-Carstensen (Conseil Permanent International, 1929) some of 

 the results of which are shown on figures 133 and 134, respectively. 

 The Dana's observations taken June to July, 1925 when plotted 

 on figure 133 show that the core of warmest water (Irminger-Atlantic 

 Current) sank from a depth of about 200 meters to a depth of about 



"According to Davis (1899, p. 18) the rate at which unobstructed insolation is received 

 on the earth with the sun at the zenith is 75.000 thousand Icilogram caloriss per minute per 

 square mile or 54 billion kilogram calories per 12 hours. If the length of sunshine per 

 day at the equator on March 20 be taken at 12 hours and the average rate of insolation 



2 

 during that period be taken as - times the maximum then the daily rate would be about 



34.3 billion kilogram calories per square mile. Davis (1899, p. 20) gives the daily inci- 

 dent radiation in latitude 60° on June 21 and September 22 as 1.09 and 0.50 times the 

 above, respectively. A conservative estimate for July-August then is taken as 0.8, 

 whence estimating the area in question to be 310,000 square miles the average summer 



rate of insolation would be ^^'^^"gHoo"'""" °^ approximately 100 billion kilogram calories per second. 

 According to Milhorn (1929, p. 41) about 60 percent is transmitted and of this about 

 two-thirds is absorbed by the atmosphere so that about 20 billion kilogram calories per 

 second reaches the ocean surface. 



