Temperature.—At the solstices the two poles receive the largest amounts of insolation which any part of the earth’s surface ever receives. It would seem, therefore, that the temperatures at the poles should then be the highest in the world, but as a matter of fact they are nearly or quite the lowest. Temperatures do not follow insolation in this case because much of the latter never reaches the earth’s surface; because most of the energy which does reach the surface is expended in melting the snow and ice of the polar areas; and because the water areas are large, and the duration of insolation is short.
A set of monthly isothermal charts of the north polar area, based on all available observations, has been prepared by H. Mohn and published in the volume on Meteorology of the Nansen expedition. In the winter months there are three cold poles, in Siberia, in Greenland and at the pole itself. In January the mean temperatures at these three cold poles are -49°, -40° and -40° respectively. The Siberian cold pole becomes a maximum of temperature during the summer, but the Greenland and polar minima remain throughout the year. In July the temperature distribution shows considerable uniformity; the gradients are relatively weak. A large area in the interior of Greenland, and one of about equal extent around the pole, are within the isotherm of 32°. For the year a large area around the pole is enclosed by the isotherm of -4°, with an isotherm of the same value in the interior of Greenland, but a local area of -7.6° is noted in Greenland, and one of -11.2° is centred at lat. 80° N. and long. 170° E.
The north polar chart of annual range of temperature shows a maximum range of about 120° in Siberia; of 80° in North America; of 75.6° at the North Pole, and of 72° in Greenland. The North Pole obviously has a continental climate. The minimum ranges are on the Atlantic and Pacific Oceans. The mean annual isanomalies show that the interior of Greenland has a negative anomaly in all months. The Norwegian sea area is 45° too warm in January and February. Siberia has +10.8° in summer, and -45° in January. Between Bering Strait and the pole there is a negative anomaly in all months. The influence of the Gulf Stream drift is clearly seen on the chart, as it is also on that of mean annual ranges.
For the North Pole Mohn gives the following results, obtained by graphic methods:—
Mean Temperatures at the North Pole.
| Jan. | Feb. | Mar. | Apr. | May. | June. | July. | Aug. | Sept. | Oct. | Nov. | Dec. | Year. |
| -41.8° | -41.8° | -31.0° | -18.4° | 8.6° | 28.4° | 30.2° | 26.6° | 8.6° | -11.2° | -27.4° | -36.4° | -8.9° |
It appears that the region about the North Pole is the coldest place in the northern hemisphere for the mean of the year, and that the interior ice desert of Greenland, together with the inner polar area, are together the coldest parts of the northern hemisphere in July. In January, however, Verkhoyansk, in north-eastern Siberia, just within the Arctic circle, has a mean temperature of about -60°, while the inner polar area and the northern interior of Greenland have only -40°. Thus far no minima as low as those of north-eastern Siberia have been recorded in the Arctic.
For the Antarctic our knowledge is still very fragmentary, and relates chiefly to the summer months. Hann has determined the mean temperatures of the higher southern latitudes as follows:—[6]
Mean Temperatures of High Southern Latitudes.
| S. Lat. | 50° | 60° | 70° | 80° |
| Mean Annual | 41.9 | 28.4 | 11.3 | -3.6 |
| January | 46.9 | 37.8 | 30.6 | 20.3 |
| July | 37.2 | 18.3 | -8.0 | -24.7 |