NO. 6 PAST CLIMATE OF NORTH POLAR REGION BERRY 29 



ried into the Arctic basin by rivers in the formation of ice and the 

 efifect of current-borne ice in maintaining subnormal density and con- 

 sequently the identity of the present day cold currents as they move 

 southward. Once they become of normal density they disappear below 

 the surface and lose their climatic influence. 



Another factor of considerable importance climatically, especially 

 in connection with the theory of Brooks, is the amount of reflection 

 from the earth's surface. I do not have the exact figures, but estimates 

 given to me orally by W. J. Humphreys, are about 7 per cent from 

 land or water and about 70 i>er cent, or ten times as much, from the 

 surface of snow and ice. If there has been the wide fluctuations in 

 polar ice as Brooks predicts, then reflection is a factor which can not 

 be safely neglected. 



At the present time in high latitudes the prevailing wind circula- 

 tion is easterly with a southward moving component at the surface. 

 If the ice cap were gone we would have westerly winds in high lati- 

 tudes with a poleward component at the surface. 



If Bering Strait was open and less shallow, a great volume of warm 

 Pacific water would pour into the Arctic and greatly ameliorate the 

 climate, as would also be the case if a Cretaceous seaway bisected 

 North America, or a Devonian or Eocene seaway bisected Eurasia, 

 such as are shown on current paleogeographic maps. If the best avail- 

 able sources are utilized in plotting Eocene seaways nearly all the 

 Tertiary coal occurrences and floras in the Arctic range themselves 

 along the easterly coasts of such seaways. 



CONCLUSIONS 



The major factor in the polar extent of temi)erate floras is 

 not primarily the direct effect of temperature so much as it is the fact 

 that above 32° F. water is a liquid and Itelow 32° F. it is a solid. Asa 

 Gray said " Plants are the thermometers of the ages." I have no 

 doubt that terrestrial vegetation when properly interpreted is the safest 

 guide to geological climates, but as thermometers they are pretty 

 poor and we have no means of calibrating them. 



There is no unequivocal botanical evidence of tropical or subtropical 

 climates at any time in the Arctic. There is no evidence from paleo- 

 botany of a lack of climatic zonation at any geological period from 

 which fossil plants are known, although at such times the evidence 

 points to a relative mildness and a lack of sharp zonation, as com- 

 pared with the present. 



The distribution of the known fossil Arctic floras with resjiect 

 t(j the present pole ])roves conclusively, as Seward pointed out in 

 1892 (p. 53). tliat tliere could have been no wandering pole. 



