DISTRIBUTION OF THE PACK-ICE 



IN THE 

 SOUTHERN OCEAN 



By N. A. Mackintosh, D.Sc. and H. F. P. Herdman, M.Sc. 

 (Plates LXIX-XCV) 



INTRODUCTION 



The purpose of this paper is to furnish information on the limits of the Antarctic sea 

 ice at different times of year, and it is hoped that it will be of some assistance both to 

 the study of oceanographical problems in the Southern Ocean and to the navigation of 

 ships in high southern latitudes. We have attempted little more than to plot a number of 

 records of the observed position of the northern fringe of the pack-ice, and to indicate, 

 so far as the data permit, in what latitudes the ice-edge is most likely to be found at 

 different times of year. We have not set out to discuss the factors which control the 

 distribution of the ice nor to describe the processes of its formation and disintegration. 



It will be realized that this paper is only a preliminary consideration of a large and 

 complex subject. The available observations are quite inadequate for a detailed account 

 of the distribution and movements of the pack-ice as a whole, especially in the winter 

 months, but the times and places at which additional records are most needed can be 

 seen at once from the charts. However, we have been able to assemble a considerable 

 number of records for the summer months from many parts of the Southern Ocean, and 

 sufficient for the winter months to give at least a rough indication of the seasonal advance 

 and retreat of the ice-edge. 



There is very little published work on the broad distribution of the Antarctic pack- 

 ice edge ; in fact a paper by Hansen (1934) appears to be the only account of the varying 

 limits of the pack-ice in any large part of the Southern Ocean. This is a short paper 

 illustrated by a set of charts showing the positions of the ice-edge at different times on 

 the southern whaling grounds in the seasons 1929-30, 1930-1, 1932-3 and 1933-4. 

 These charts were based on the positions, at monthly or half-monthly intervals, of 

 whaling factory ships working at the ice-edge, and they constitute a most valuable 

 record of the changes in the distribution of the pack-ice in those four Antarctic summers. 

 They only cover, however, the area between 40 W and no° E and the period from 

 October to March. Subsequently an Atlas over Antarktis og Sydishavet was compiled 

 by Hansen and published by the Norsk Hvalfangernes Assuranceforening, and in this 

 is included a chart showing the approximate mean positions of the ice-edge in November, 

 December, January and March in all except the Pacific sector, and in January and March 

 in the Pacific sector also. This again is derived mainly from records from the whaling 



