178 MAKION EXPEDITION TO DAVIS STRAIT AND BAFFIN BAY 



meltiii<r <>i^ ice alonji; the coast or over the coiitineiital shelves. The 

 expansion and recession of reservoirs of lifj^ht water ahing- the 

 inar<»:in of the current are especially sirrnificant in this connection. 

 The greater the quantity and the lower the specific <>ravity of these 

 masses, the steeper becomes the gradient and the greater the velocity 

 and volume of the flow. The principal sources that contribute this 

 coastal supply of light water are the melting ice/' and the drainage 

 from the bordering land areas. Since contributions are at their 

 maximum in sj)ring and summer, their effect in imparting, therefore, 

 a seasonal variation to the fringing ocean current is cunudative 

 Avith that of the wind. Such oceanographic observations on the 

 Labrador current as are at hand have been collected mostly in sum- 

 mer, and in the region south of Newfoundland. Tlie investigations 

 of the ice patrol, which embrace 1)5 per cent of the total, have been 

 very scanty in February and March, but voluminous and in detail 

 from May to July, wath only one survey in October. 19'23. Few 

 observations have been taken of the current north of Newfoundland, 

 excej^t for those collected by the Chance in the summer of 11>26. and 

 by the Mar'ion expedition and the Godthaah expeditions in the sum- 

 mer of 1928. The volume and strength of tlie Labrador current 

 around the (xrand Bank, as shown by comparing the ice })atrors data 

 of temj^erature, salinitv, and dynamic topography from vear to vear 

 (see Fries 1922, p. GlfSmith 1923, p. 84; 1924, p. 109: and 1924a, p.. 

 98), indicates the occurrence of seasonal variations. In normal 

 years, at least according to the foregoing observations from around 

 the Grand Bank, the cold current appears to reach a nuiximum 

 during spring and early summer, after which it dwindles to a 

 minimum in fall and winter. The fact that little Arctic ice drifts 

 into the Atlantic during fall and early winter may also indicate that 

 the Labrador current is then interrupted. It should be noted, 

 however, that no year-round observations have yet been made from 

 several sections distributed over the entire length of the Labrador 

 current, and until they are collected we can not reach final 

 conclusions. 



The Labrador current is also marked by fre(iuent irregular pulsa- 

 tions occurring witliin the interval of a few weeks, or of a month or 

 two, all of which tends to mask the more important major cycle. 

 (See figs. 99. 100, and 101.) These secondary short-term fluctuations 

 may hark back to corresponding excesses or deficiencies developing in 

 the light water along the continental slope from time to time. For 

 example, a period of warm, wet weather around Xewf<Huidland may 

 appreciably accelerate the melting of the coastal ice and the discharge 

 from the rivers, increasing the supply of light water, thus swelling 

 the mass and the velocity of the southern end of the cold current. 

 Under such conditions any ice in that particular locality will move 

 south faster than will the ice situated farther north, although the 



■' Many statements have appeared in print tliat tho cold Arctic currents are auamented 

 b.V Rreat quantities of ice wliieli are melted every sum'mer in the far north. Tlio impres- 

 sion is therefore s'iven that excess masses of lis'ht water or a hijih level at a rivcrlike 

 source (in Baffin Bay for the Labrador current) constitutes the n(>ct'ssary head to dis- 

 charge the water downs! rram into the Atlantic. It is hiirh time that the river idea be 

 discarded when considcrini; unrestruted lUovenKMits on a rotatin.u spliere. under which 

 class behuig (jcean currents. The pressure gradient which impels I lie stream tli>\v of water 

 lies on tlie right-hand side of the current in the northern hemisplierc. Th(>reton'. in order 

 for thaw water to assist the flow of the I.al)radoi- current, the ice must lie distrilaited and 

 melt, not in Baffin Bay or the I'olar Basin, hut along the shelves ot Baffin Land. Labrador, 

 and Newfoundland. 



