CLIMATOLOGICAL PROBLEMS IN THE ARCTIC AND SUB-ARCTIC 
influenced by the idea of ‘dynamic climatology” put 
forward by Bergeron. Borisov’s study is illustrated by 
numerous distribution maps, some of them drawn from 
the U.S. S. R. Great Soviet World Atlas [61], and all of 
them emerging from official sources. An invaluable 
supplement is the exhaustive study of Tikhomirovy [58] 
on the Arctic and sub-Arctic of Soviet Asia. Tikhomirov 
presents tabulated summaries of the chief observa- 
tional data from most of the new Siberian stations 
set up since 1930 by the resurgent Soviet states. A 
general review of Russian climates from the point of 
view of the normal circulation has been given by 
Alisov [1]. 
To these general studies must be added a large 
volume of local or specialised work scattered through 
the literature, almost entirely from Scandinavian 
sources. When reading either the general studies or 
the more specialised papers, one should bear in mind 
the scattered nature of the observations upon which 
they are based. The peninsula of Labrador-Ungava 
may be taken as an instance. This great land mass has 
an area of over 500,000 square miles; from north to 
south the peninsula extends over 14° of latitude, the 
same span as that separating New York and Palm 
Beach, Florida, and in longitude it extends over 22°, a 
distance equivalent to that separating New York from 
Minneapolis. In area, the peninsula is thus equivalent 
to the whole of United States territory lying east of 
the Mississippi and south of latitude 40°. Yet in the 
whole of this area there were no inland climatological 
stations before 1915, and only one from 1915-37 
(Mistassini Post). Today there are ten, corresponding 
to less than one per state in the southeastern United 
States as defined above. 
It is plain, then, that the time for comprehensive 
climatological synthesis is far distant. Yet there are 
many specialised fields in which the climatologist can 
work, and in which much valuable material has already 
been published. The author has selected for discussion 
below those special fields of research that seem to him 
most profitable with our present limited resources. 
They are: 
1. The ecological climatology of the Arctic and sub- 
Arctic, a field that tends to be neglected by the cli- 
matologist; and 
2. The climatological relation of sea ice, a vast and 
disorderly field in which much research is now pro- 
gressing. 
In addition, some attention is given below to the 
highly significant question of Greenland’s icecap climate, 
a topic much bedevilled by controversy. 
Inevitably this selection omits many subjects con- 
sidered important by others. Prominent among these 
will be the physical characteristics of arctic snow cover. 
Restrictions in space and the author’s experience must 
excuse these omissions. 
ECOLOGICAL CLIMATOLOGY 
The relation of climate to natural vegetation is one 
of the most significant branches of modern climatology. 
Vegetation and soils are mirrors of the normal climate 
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of a region; the concepts of climax vegetation and of 
the great world soil groups both depend on the idea 
that climate is the ultimate ecological control. There is 
fairly general agreement that the type of fully de- 
veloped natural vegetation and the mature soil profile 
are faithful climatic indicators. Soil and vegetation 
maps divided into regions ought therefore to give us a 
useful method of defining rational climatic regions. 
Most systems of climatic classification, like those of 
K6ppen [86] and Thornthwaite [56, 57], have been 
based upon this assumption. 
The ecological approach to climatology is especially 
valuable in the Arctic and sub-Arctic, for these are 
by definition major world regions in which climate 
restricts growth and economic potential through the 
agency of excessive cold. The natural vegetation of 
the cold northern lands falls into two major formations: 
1. The tundra, the truly arctic landscape with no 
tree growth, where the dominant plants are the sedges, 
rushes, mosses and lichens, with some small shrubs and 
bushes. Very little work has been done on the climatic 
relations of the tundra in North America, and the 
Russian tundra is still being mapped. 
2. The Boreal forest, which is the term applied to 
the great forest formation that everywhere borders 
the tundra along the latter’s southern flank. The tundra 
and Boreal forest formations are separated by a transi- 
tion zone in which both occur, the so-called forest- 
tundra, or forest-tundra ecotone.2 The arctic tree line is 
the extreme northern limit of tree growth and may in 
general be regarded as the northern edge of the forest- 
tundra. As so defined, the line is the absolute northern 
limit, not of the forest, but of patchy and often stunted 
tree growth, extensive islands or “peninsulas”’ of tun- 
dra associations lying to the south of it. 
Tundra associations occur in places far south of the 
true arctic limit. These anomalous areas occur in two 
types of environment: (1) on high ground, where the 
effect of altitude lowers the summer temperatures to 
the point at which only tundra vegetation can be sup- 
ported (this is the so-called alpine tundra, and one 
also speaks of the alpine tree line); and (2) on certain 
exposed coasts in high latitudes, as for example in 
Labrador, Iceland, and parts of Arctic Scandinavia (to 
these anomalies the term “maritime tundra’? may be 
applied). 
The Nature of Climatic Control. It has long been 
assumed that temperature and the length of the grow- 
ing season are the climatic elements controlling the 
distribution of climax vegetation in the north. It is a 
demonstrable fact that imterformational boundaries 
tend to follow the general trend of the mean isotherms 
across continental masses. This correlation of the great 
vegetation regions with thermal climate has been used 
by such climatologists as Képpen and Thornthwaite 
to define climatic boundaries, which will be discussed 
later. Thornthwaite explicitly states [56, p. 648] that 
in the cold climates restriction of growth by cold far 
2. The term ecotone is used ecologically to indicate a zone 
of transition from one major plant community to another. 
See Weaver and Clements [64, p. 104]. 
