Ice alias of Arctic Canada. C. W. M. Swithinbank Ottawa, Defence Research Board, 1960. [ii], 67 p., 67 figs. $7.50. (Obtainable from the Queen's Printer, Ottawa.)

Abstract

WHEN cautiously used, charts of the occurrence of sea ice would be useful to seamen in Canadian Arctic waters; these charts com piled by Dr. Swithinbank should also be studied in deta il by scientists with interests in polar seas. There are 29 charts showing by sector diagrams the freq uency of occurrence of ice derived from 29 ice summary diagrams. In addition there is a reference chart showing the numbered locations of stations, one showing mean surface currents and five monthly charts showing the mean extent of fast ice.The cartograph y is pleasing, both in style and definition. On the frequency charts the base chart is printed in dark grey, the outline of the circles of the sector diagrams in black, and the ice formation in clearly contrasting colours. Perhaps the registration might have been more precise but this is a minor criticism. It is agreeable to see the legend repeated on each page and also the clearly printed dates at the head of each sheet. The size of the atlas is somewhat cumbersome, 34 X 20 in. (86 X 51 cm.), but this is understandable as the area studied stretches from the north coast of Alaska, from Icy Cape eastwards through Canadian Arctic waters to West Greenland waters north of Disko Bugt. It is somewhat regrettable that the projection is not stated.This reviewer is particularly conscious of the patience needed in accumulating so many data from so many sources in a number of countries. Dr. Swithinbank explains in a short but admirable text the method employed in making the ice summary diagrams and from these the frequen cy charts. It is also well worth while to read his pa per (1958) on the compilation of this atlas, presented at the 1958 conference on Arctic sea ice. I ce data collected from ships' logs, 1900-58, and from aerial observations obtained from the U.S. Hydrographic Office, from 1952 onwards, were plotted on 998 separate weekly plotting charts (a sample of which is given in the atlas as Figure 38) covering 1 March to 30 November. This information was tabulated for the 324 reference stations in the ice summary diagrams, one for the whole month of March, two for April, weekly for May to October, and two for November. The sector diagrams, plotted at the position of the reference stations on the frequency charts, were constructed by collating all the materia l for one week, or other selected period, given in the ice summary diagrams ; different colours denote varying ice conditions, and each sector of the circle represents a proportion of years in which ice ofa particular concentration was observed. It is apparent from the text, as well as from the diagrams, that the emphasis is on the effect of sea ice on shipping and there is a careful statement of the possible relationships between ice concentration as measured in tenths of the sea surface covered and the navigability of such ice.