142 MARION AND GENERAL GREENE EXPEDITIONS 



rent swells to maximum volume in the spring and dwindles or dis- 

 appears from the Grand Banks region in the fall and winter. The 

 underlying factor is attributed to summertime insolation with the 

 consequent release of water from melting snow and ice, the Labrador 

 Current acting as a freshet overflows southward deeper into the North 

 Atlantic.^* But a spring freshet in the Grand Banks sector, con- 

 sidering the distances from the source region and the rate of trans- 

 port of such a flood wave, comes much too early to connect with 

 summer or even vernal warming. 



The common impression that the Labrador and the East Greenland 

 Currents display a seasonal variation may have been largely abetted 

 by the drift of the sea ice and the icebergs south of Newfoundland, 

 a well-known phenomenon which is subject to a conspicuous annual 

 cycle. Any marked correlation between the abundance of sea ice 

 south of Newfoundland and vernal warming is discountenanced, 

 however, by the fact that the seasonal maximum of the former pre- 

 cedes the latter. The cycle in the sea ice is traceable apparently to 

 a seasonal rate of production during winter and the consequent 

 southward drift from its source. The sequence of events is quite in 

 harmonj^, moreover, with a uniform velocity of the currents pre- 

 viously described. 



The seasonal cycle of icebergs south of Newfoundland which 

 reaches a maximum usually in May is also somewhat too early to be 

 caused by a freshet of the cold current predicated on vernal warming. 

 The iceberg cycle, on the other hand, as proven by Smith (1931), 

 correlates with the cycle of the pack ice, and is believed primarily 

 dependent upon a "fence" of pack ice along the Labrador coast dur- 

 ing late winter and early sprmg. This also is a condition obviously 

 quite unrelated to a cyclical phase, if any, in the Labrador Current. 

 An annual cycle of the Labrador Current based upon the cyclical 

 drift of pack ice and icebergs south of Newfoundland is, therefore, 

 in view of the above, considered a delusion. 



The impression that Arctic currents, noticeably their southern 

 extensions, dwindle and in many places disappear during late sum- 

 mer and autumn, may have been gained from the temperature of 

 the water. Naturally different temperature criteria for the axis of 

 the cold current must be employed during late summer and autumn 

 than at other times due purely to solar warming and mixing to 

 which the upper layers are subject. The East Greenland polar con- 

 stituent of the West Greenland Current, for example, along the coast 

 north of Cape Farewell, often loses its negative character in late 

 summer, yet comparison between the velocity and temperature pro- 

 files proves its presence nevertheless. Higher average subsurface 

 temperatures were noted in the axis of tlie Labrador Current in 

 Grand Banks sector by Smith (1924, p. 102) and attributed not to 

 any slacking in the cold current but primarily to a milder 1923-24 

 winter. 



Surface temperature maps of the Grand Banks sector compiled by 

 the Ice Patrol in June and July have proved quite misleading regard- 



'* BiKelow (lf>27) found that tlic No'ji Scotian Curront cxpcrii'iices freshet charac- 

 teristics when during a few weeks in spring it flows into the Gulf of Maine. 



