clockwise in a circular system (Gordienko). 
(See Polar Record, Vol. 9, No. 63, 1959, p.617, Recent 
Polar Literature: Thorén, Ragnar. Fotografisk rekog- 
noscering och tolkning av havsisen 1 Arktis. Ymer, 
Arg. 78, Hft. h, 1958, p.263-T9, illus., map. (Aerial 
photographic reconnaissance and interpretation of sea 
ice in Arctic; conditions and movements of sea ice in 
Arctic Ocean. English summary.)) 
NORTH FOLAR ICE 
The term Polar Ice means the thickest and heaviest 
form of sea ice which is more than one year old. Polar 
Ice, therefore, is always older and as a rule thicker, 
: too, than Winter Ice, formed and developed in one win- 
ter. Old ice of the type Polar Ice is common, broadly 
speaking, everywhere in the center of the Arctic Ocean, 
see Figure 2. Several years old ice 1s often called 
North Polar Ice. This special type of ice is to be 
found primarily in the eastern half of the Polar Basin, 
north of Alaska and East Siberia, from which area it ex- 
tends as vast fields of pack ice in a direction towards 
the North Pole and the north coast of Greenland. Inter- 
spersed in fields of North Polar Ice are patches of 
younger ice, where water openings from the preceding 
summer have become frozen. The ice thickness is normal- 
ly 10 to 13 feet or 3 to h m. At pressure ridges, how- 
ever, the thickness is increased considerably - 40 feet 
or about 12 m. is notunusual. The total surface of the 
field is crisscrossed by pressure ridges, often in a 
zigzag pattern. 
As an example of North Polar Ice in close-ups in 
Figures 3-4 there are photos from the Beaufort Sea at 
the north coast of Alaska, taken by the author during 
ice reconnaissance in August 1955. It is the Polar Pack 
that is in motion. This North Polar Ice is several years 
old and is hard as steel. 
The ice floes often appear in the most fantastic 
forms in blue, green and white, which ought preferably 
to be reproduced in color. Blocks and floes, several 
years old, are usually eroded at the water line. Sub- 
merged parts of many floes are projecting as dangerous 
rams, as can be clearly seen in Figure 3. Erosion at 
the water line and the melting of the upper ice layers 
explain the development of the ram. It is worth notic- 
ing, however, that the main part - or ebt. 7/8tns of the 
total mass of the ice - always belong to the submerged 
part of the floes. 
ARCTIC ICE ISLANDS 
Ice Islands is the designation given to floating, 
larger or smaller ice fields of considerable age and 
thickness. They differ from the surrounding pack ice 
especially by their characteristic "rolled" surface. 
This type of ice was first discovered during the 19h0s, 
by the U.S. Air Force, and is to be found as large fields 
in the Polar Basin off the Canadian arctic archipelago 
or as smaller islands which have found their way into 
the channels of this archipelago. To-day there seems 
to be only one opinion as regards their origin, i.e. 
that they are separate offspring sections of the shelf 
ice at the north coast of Ellesmere Island, the so- 
called Ellesmere Ice Shelf. The thickness is, as men- 
tioned above, considerable, attaining about 150 feet or 
45 m. as regards the larger islands. It is on such an 
ice island, called T 3, that the Americans have one of 
their polar stations in action. 
At the discovery of the ice islands, as well as at 
the exploration of their actual origin, photographic 
reconnaissance and photo interpretation were used with 
great success. The same valuable aids have been used in 
localizing the islands again to register their tracks. 
As a result science has also got important information 
as regards the ocean currents, and the slow, clockwise 
circular motion in the "inner" part of the Arctic Ocean. 
(See: 
Baird, P.D. 1955.  "Glaciological Research in the 
Canadian Arctic". Arctic, Vol. 8, Nr 2. 
Browne, I.M. and A.P. Crary. 1958. "The Movement of 
Ice in the Arctic Ocean". Paper presented to the 
Arctic Sea Ice Conference, Washington (Easton), 
U.S.A., 1958. 
Crary, A.P., R.D. Cotell, and T.F. Sexton. 1952. 
"Preliminary Report on Scientific Work on "Fletcher's 
Ice Island", T 3". Arctic, Vol. 5, Nr L. 
Hattersley-Smith, G. and others. 1955. "Northern 
Ellesmere Island, 1953 and 1954". Arctic, Vol. 8, 
Nr 1. 
Hattersley-Smith, G. 1957. "The Rolls on the Elles- 
mere Ice Shelf". Arctic, Vol. 10, Nr 1. 
Koenig, L.S., K.R. Greenaway, Moira Dunbar, and 
G. Hattersley-Smith. 1952. "Arctic Ice Islands". 
Arctic, Vol. 5, Nr 2. 
Marshall, Ernest W. 1955. "Structural and Strati- 
graphic Studies of the Northern Ellesmere Ice Shelf". 
Arctic, Vol. 8, Nr 2. 
Montgomery, Margaret R. 1952. "Further Notes on Ice 
Islands in the Canadian Arctic". Arctic, Vol. 5, 
Nr 3.) 
DISINTEGRATION OF SEA.ICE 
Fields of se& ice or pack ice interrupted with areas 
of water, e.g. leads or lanes, polynyas and pools be- 
tween the floes, or depressions on ice filled with melt 
water, so-called puddles, will absorb considerably more 
radiant heat than a continuous ice or snow surface. As 
goon as free water surfaces appear, the rate of further 
disintegration of an ice sheet is much accelerated. 
Photographic reconnaissance and continuous interpre- 
tation of aerial photos of sea ice areas, with special 
regard to free water surfaces, are therefore of import- 
ance for estimating the speed of disintegration of the 
ice and forecasting the trafficability or possibilities 
of shipping. 
In the same way as free water surfaces accelerate the 
disintegration of an ice field, accumulation of dust or 
film of diatoms will speed up the melting process. As 
regards fast ice, the ice generally disappears first in 
the coastal zone where it has got a thin cover of wind- 
blown sand or dust from rocks ashore. Such "shore 
leads" are of special importance for the navigability 
in areas where the ice conditions are otherwise severe 
and perhaps render shipping impossible. Photographic 
reconnaissance and photo interpretation are, quite 
naturally, a good air for shipping also under these 
circumstances. 
MISCELLANEOUS NOTES OF INTEREST 
The Baltic Ice Code 
In September 1959 the Swedish Meteorological and 
Hydrological Institute published The Baltic Ice Code 
in Swedish and English with illustrations. The des- 
cription is written by Dr. Bertil Rodhe, First State 
Meteorologist at this Institute, Stockholm, in close 
cooperation with representatives of the Ice Reporting 
Services in Denmark, Finland, Norway, Sweden and 
Western Germany. There are 45 photographs, high and 
low obliques and ground photos as well, illustrating 
the Character of the Ice and the Ice Development in 
different situations. They are really good examples, 
suitable to be used as an Ice Key to photo interpre- 
ters. 
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