CHAPTER II TEMPERATURE L-ADELIE LAND AND QUEEN MARY LAND 1.—INSTRUMENTS AND METHODS. Notes regarding the instruments and their exposure at Adelie Land are given in Volume IV of this series containing the "tabulated and reduced records". The tabulated values were derived from the records of a weekly thermograph by Messrs. Short & Mason, Ltd. in which the recording element was a bimetallic spiral. No details regarding the instrument are given. The usual difficulties due to the severity of Antarctic conditions were experienced. Drifting snow was especially troublesome owing to the almost continuous high winds. The readings of the thermograph were, however, controlled by those of mercury thermometers and the final accuracy may be regarded as quite satisfactory. In addition to hourly values, the daily maximum and minimum were read from the thermograph traces. These, together with their time of occurrence and the daily range as derived from them, are tabulated for each day. At Queen Mary Land the procedure was very much the same, but the thermograph gave considerable trouble and there are a number of long breaks in the record. These are filled to a certain extent by the three-hourly eye observations, but in some months the number of days with no observations is still considerable. In the tabulations contained in Volumes II, III, and IV of this series, it was the general practice not to give a daily mean for days when some observations were missing, or to use these days in determining the diurnal variation. For the purposes of the present discussion the gaps have been filled wherever possible. In some cases, probable values could be got by reference to the original records, but in other cases interpolations had to be made. At Queen Mary Land, when 3-hourly observations are available, it is clear that a satisfactory daily mean can be obtained, while hourly values can be interpolated to a close degree of approximation. In consequence of this incorporation of additional values, and of errors in computation in the original tables, it will frequently be found that the figures used in this volume differ from those printed in the others. These remarks apply to other elements besides temperature. 2.—TOPOGRAPHY. The location of the two Bases in reference to the Southern Ocean and the Antarctic Continent is shown in Fig. 1. A more detailed map of the Adelie Land and King George V Land region is given in Fig. 2. The coastline runs fairly evenly in a west- northwest to east-southeast direction but is indented by a number of bays, on one of which, Commonwealth Bay, the expedition's headquarters were situated. It is important to notice that for over 50 miles to the eastward and over 100 to the westward, there was open sea at all times of year. Further to the eastward, there were the great tongues of the Mertz and Ninnis glaciers with fields of floe ice attached to them, while to the west, beyond the distance mentioned, impenetrable pack extended for many miles off-shore. 13 14 AUSTEALASIAE" ANTAKOTIC EXPEDITION. Around the Base itself was an area of exposed or semi-exposed rock surface, consisting of granitic gneiss and some morainic material, but this was too small to exercise any important influence on. the thermal conditions. Polar equidistant projection Scale at on a meridians FIG. 1. The slopes of the great ice shelf of the Antarctic Continent rise from the shore probably to the centre of the continent. At the furthest point reached by the Southern Party under Kobert Bage, which was approximately 150 miles inland, the ice surface was 6,000 feet (1,800m.) above sea level. The main ice divide to the southward is unlikely anywhere to be less than 7,000 feet (2km.) in altitude and it may be anything from 200 miles to 1,000 miles and more from the coast in different directions. Certainly the coast in this region must receive the drainage of cold air from an enormous hinterland. The sea being kept open on the coast, a temperature of 28° F. and upwards must be main­ tained there. In any but the warmest summer months, therefore, there must be a very marked contrast between the thermal conditions on either side of the shore line. There was, consequently, an almost continuous rush of cooled air from the interior out over H O W O fi O MAIN BASE LOCALITY FIG. 2. AUSTRALASIAN ANTARCTIC EXPEDITION WESTERN BASE LOCALITY SCALE — STATUTE Ml LBS 10 5 0 10 20 30 40 SO m i—i izj H Q M Q M / ' HENDERSON, ' / y . ' I H3 I—I O ,..:,-.;LAN 5a FIG. 3. METEOROLOGY. 17 the sea. The regular downward slope from the interior would prevent any stagnation of cold air. Directly its density became greater than that of the free air at the same level, air cooled by the snow surface would be carried by gravity down the slope towards the sea. The temperature of the sheet of downward flowing cooled air could, therefore, never be very greatly below that of the air above it. Though the temperature at Adelie Land should, therefore, be lower than that some distance off-shore, it should be much higher than that over level or only very gently sloping ice-surfaces such as the Great Ross Barrier and parts of the interior of the continent. The comparatively steep slope of the land surface and the presence of the open sea on the coast ensure that cooled air is drained off the land by a continuous process, whereas in the Ross Sea region accumulations are removed by occasional blizzards when the pressure distribution favours southerly winds. Owing to the continued strong winds one would expect rather small annual and diurnal variations of temperature, and generally speaking the temperature should be much steadier than in, for instance, McMurdo Sound where it is possible for an intensely cold layer to form over the snow or ice surface. At Queen Mary Land, the base was on a floating tongue of shelf-ice with a level top, some distance (about 14 miles) from the shores of the continent. The conditions were, therefore, very different from those at Adelie Land and the cold layer was fre­ quently in existence. A detailed map of the region adjacent to the Queen Mary Land base station appears as Fig. 3. 3.—THE TEMPERATURE OBSERVATIONS. Mean Temperatures.—The monthly mean temperatures deduced from tabulations of the hourly values are given in Table I. The annual variation as derived from all the observations is given in Fig. 4. The mean temperature is 8.9° F. at Adelie Land, which II IV V VI VII VIII IX XI XII FIG. 4.—Annual Variation of Temperature. * 2636—B 18 AUSTRALASIAN ANTARCTIC EXPEDITION. TABLE I. Temperature—Monthly Means. Degrees Fahrenheit. Year. I. II. III. IV. V. VI. VII. VIII. IX. X. XI. XII. Mean. Ad elie L a,nd. 1912 .. 22-8 11-0 1-9 —3-4 —6-8 —4-2 —2-5 —1-7 71 181 26-8 1913 30-3 25-3 13-6 2-5 1-9 —2-0 —2-8 1-3 —1-3 2-3 16-3 27-4* Means 30-3 24-0 12-3 2-2 —0-8 —3-5 —0-6 —1-5 4-7 17-2 270 8-9 * From 14 days only, weighted Queen Mary Land. 1912 4-8* —30 —7-5 —15-2 —1-9 —4-9 1-8 9-3 17-8 24-8 I 5-8 1913 23-1 20-2 * Many days are missing in March, April, October, and February; see Tables in Vol. V. TABLE II. Temperature—Harmonic Analysis of Annual Variation. HI = ax sin (0 + Ax) + a2 sin (20 + A2) + o3 sin (39 + A3). Adelie Laud. Queen Mary Land. « 1 A, a, A, a A. l Ax °» A, o» A. O O o °F. °F. °F. °F. O "F. 0 °F. O 16.5 81 4'8 68 0-7 110 17-2 97 3-2 54 0-7 185 METEOKOLOGY. 19 may be compared with 0.7° F. for McMurdo Sound* 7.0° F. for Cape Adaref, and -14.4° F. for Framheimf. The mean derived from one year's observations at Queen Mary Land is only 5.8° F. but for corresponding periods the Queen Mary Land mean is only 2.7° F. below that of Adelie Land. Similarly, during the eleven months of 1912 when records were being obtained contemporaneously at the two stations, the temperature at Cape Evans was only 4.4° F., in the mean, below that at Adelie Land. 1912 was the windiest year experienced in McMurdo Sound. J. 5,—Temperature at Southern Stations. The mean temperatures at numbers of Southern Hemisphere stations south of Latitude 40° are compared in Fig. 5. Between Latitudes 40° and 50° the rate of decrease * E. Kidson. British Antarctic Expedition. 1907-1909, Meteorology, Melbourne, page 20. •f G. C. Simpson. British Antarctic Expedition. 1910-1913, Meteorology, Vol. I, page 83. 20 AUSTKALASIAN ANTAKCTIC EXPEDITION. of temperature appears relatively small. Thereafter there is a rapid decrease until the Antarctic Circle is reached. Between Macquarie Island and Adelie Land the rate is 2.5° F. per degree of Latitude. This is a region of very strong westerly winds and the general circulation is very active. The figure suggests that the temperature in the free air falls off at a reduced rate again between the Antarctic Circle and the Pole. In the summer, the gradient is very slight. The actual surface temperature recorded at these high latitudes depends very much on the nature of the exposure.