The Geographical Journal (Journal of the Royal Geographical Society): Volume XII, No. 2 [‎264v] (31/154)

122 THE ANNUAL RANGE OF TEMPERATURE IN THE SURFACE WATERS OF THE
approximation of the range of temperature. In the southern hemisphere
south of the 60th parallel, our maps are almost a complete blank, the
observations being limited to those taken in the summer by Ross and
other antarctic explorers. In the northern hemisphere, on the other
hand, we have a good deal of information. As already stated, Makaroff
records numerous observations north of 60° N., extending as far north
as 76° N., in the North Pacific, and in the North Atlantic we have been
able, approximately, to estimate the range of temperature as far as
82° N., from the observations and maps published by Mohn in the
Norwegian North Atlantic Expedition Report, from Koldewey’s obser
vations during the German Arctic Expedition, from Nansen’s published
observations, and from records brought home by Mr. Bruce, of the
Jackson-Harmsworth Expedition, as well as other arctic explorers.
From these sources we have observations in no less than 155 squares
between lat. 60° and 82° N., and long. 26° W. and 38° E., which are
available in estimating the range of temperature.
3. General Features of the Map.
The lines on the map are drawn for intervals of 5° Fahr. of range of
temperature, and different shades of colour are used for intervals of
10° Fahr. Broadly speaking, the map shows that the surface of the
ocean may be divided into five great zones: firstly, a circumtropical
zone with high temperature and small range (coloured deep red on the
map); secondly, two circumpolar zones with low temperature and small
range (coloured pale red on the map); and lastly, two intermediate
zones with large ranges lying between the circumtropical and the two
circumpolar zones (coloured in different shades of blue on the map).
The regions indicated as having a range of less than 5° Fahr. are
largely hypothetical, more especially in the polar regions and tropical
Pacific, though the small areas laid down in the tropical Atlantic and
tropical Indian oceans are based upon numerous observations. In the
polar regions the line coincides approximately with the line of perpetual
ice.
The northern circumpolar band, with a range not exceeding 10° Fahr.,
borders the northern shores of Asia and America, lying mostly within
the arctic circle. It is probable, however, that a wider range will be
found off the mouths of many of the rivers flowing into the Arctic
ocean from America and the Eurasian continent. The corresponding
southern circumpolar band apparently approaches nearer to the tropics,
extending northwards, approximately, as far as lat. 50° S., and pene
trating to the north of that latitude in the Atlantic, but it may be
expected that more extended observations will necessitate the drawing
of the line of 10° range much nearer the antarctic circle, probably
throughout its whole extent. In these two circumpolar bands, with a
range of less than 10° Fahr., observations are meagre, and indicate