South (53 page)

The pack
is a term very often used in a wide sense to include any area of sea ice, no matter what form it takes or how disposed. The French term is
banquise de dérive.

Pack ice.
A more restricted use than the above, to include hummocky floes or close areas of young ice and light floes. Pack ice is “close” or “tight” if the floes constituting it are in contact; “open” if, for the most part, they do not touch. In both cases it hinders, but does not necessarily check, navigation; the contrary holds for

Drift ice.
Loose open ice, where the area of water exceeds that of ice. Generally drift ice is within reach of the swell, and is a stage in the breaking down of pack ice, the size of the floes being much smaller than in the latter. (Scoresby’s use of the term drift ice for pieces of ice intermediate in size between floes and brash has, however, quite died out.) The Antarctic or Arctic pack usually has a girdle or fringe of drift ice.

Brash.
Small fragments and roundish nodules; the wreck of other kinds of ice.

Bergy bits.
Pieces, about the size of a cottage, of glacier ice or of hummocky pack washed clear of snow.

Growlers.
Still smaller pieces of sea ice than the above, greenish in color, and barely showing above water level.

Crack.
Any sort of fracture or rift in the sea ice covering.

Lead
or
Lane.
Where a crack opens out to such a width as to be navigable. In the Antarctic it is customary to speak of these as leads, even when frozen over to constitute areas of young ice.

Pools.
Any enclosed water areas in the pack, where length and breadth are about equal.

The meteorological results of the Expedition, when properly worked out and correlated with those from other stations in the southern hemisphere, will be extremely valuable, both for their bearing on the science of meteorology in general, and for their practical and economic applications.

South America is, perhaps, more intimately concerned than any other country, but Australia, New Zealand, and South Africa are all affected by the weather conditions of the Antarctic. Researches are now being carried on which tend to show that the meteorology of the two hemispheres is more interdependent than was hitherto believed, so that a meteorological disturbance in one part of the world makes its presence felt, more or less remotely perhaps, all over the world.

It is evident, therefore, that a complete knowledge of the weather conditions in any part of the world, which it is understood carries with it the ability to make correct forecasts, can never be obtained unless the weather conditions in every other part are known. This makes the need for purely scientific Polar Expeditions so imperative, since our present knowledge of Arctic and Antarctic meteorology is very meager, and to a certain extent unsystematic. What is wanted is a chain of observing stations well equipped with instruments and trained observers stretching across the Antarctic continent. A series of exploring ships could supplement these observations with others made by them while cruising in the Antarctic Seas. It would pay to do this, even for the benefit accruing to farmers, sailors, and others who are so dependent on the weather.

As an instance of the value of a knowledge of Antarctic weather conditions, it may be mentioned that, as the result of observations and researches carried out at the South Orkneys—a group of sub-Antarctic islands at the entrance to the Weddell Sea—it has been found that a cold winter in that sea is a sure precursor of a drought over the maize- and cereal-bearing area of Argentina three and a half years later. To the farmers the value of this knowledge so far in advance is enormous, and since England has some three hundred million pounds sterling invested in Argentine interests, Antarctic Expeditions have proved, and will prove, their worth even from a purely commercial point of view.

I have given just this one instance to satisfy those who question the utility of Polar Expeditions, but many more could be cited.

As soon as it was apparent that no landing could be made, and that we should have to spend a winter in the ship drifting round with the pack, instruments were set up and observations taken just as if we had been ashore.

A meteorological screen or box was erected on a platform over the stern, right away from the living quarters, and in it were placed the maximum and minimum thermometers, the recording barograph, and thermograph—an instrument which writes every variation of the temperature and pressure on a sheet of paper on a revolving drum—and the standard thermometer, a very carefully manufactured thermometer, with all its errors determined and tabulated. The other thermometers were all checked from this one. On top of the screen a Robinson’s anemometer was screwed. This consisted of an upright rod, to the top of which were pivoted four arms free to revolve in a plane at right angles to it. At the end of these arms hemispherical cups were screwed. These were caught by the wind, and the arms revolved at a speed varying with the force of the wind. The speed of the wind could be read off on a dial below the arms.

In addition there was an instrument called a Dines anemometer, which supplied interesting tracings of the force, duration, and direction of the wind. There was an added advantage in the fact that the drum on which these results were recorded was comfortably housed down below, so that one could sit in a comparatively warm room and follow all the varying phases of the blizzard which was raging without. The barometer used was of the Kew standard pattern. When the ship was crushed, all the monthly records were saved, but the detailed tracings, which had been packed up in the hold, were lost. Though interesting they were not really essential. Continuous observations were made during the long drift on the floe, and while on Elephant Island the temperature was taken at midday each day as long as the thermometers lasted. The mortality amongst these instruments, especially those which were tied to a string and swung around, was very high.

A few extracts from the observations taken during 1915—the series for that year being practically complete—may be of interest. January was dull and overcast, only 7 percent of the observations recording a clear blue sky, 71 percent being completely overcast.

The percentage of clear sky increased steadily up till June and July, these months showing respectively 42 percent and 45.7 percent. In August 40 percent of the observations were clear sky, while September showed a sudden drop to 27 percent. October weather was much the same, and November was practically overcast the whole time, clear sky showing at only 8 percent of the observations. In December the sky was completely overcast for nearly 90 percent of the time.

Temperatures on the whole were fairly high, though a sudden unexpected drop in February, after a series of heavy northeasterly gales, caused the ship to be frozen in, and effectually put an end to any hopes of landing that year. The lowest temperature experienced was in July, when -35º Fahr., i.e. 67º below freezing, was reached. Fortunately, as the sea was one mass of consolidated pack, the air was dry, and many days of fine bright sunshine occurred. Later on, as the pack drifted northwards and broke up, wide lanes of water were formed, causing fogs and mist and dull overcast weather generally. In short, it may be said that in the Weddell Sea the best weather comes in winter. Unfortunately during that season the sun also disappears, so that one cannot enjoy it as much as one would like.

As a rule, too, southerly winds brought fine clear weather, with marked fall in the temperature, and those from the north were accompanied by mist, fog, and overcast skies, with comparatively high temperatures. In the Antarctic a temperature of 30º, i.e. 2º
below
freezing, is considered unbearably hot.

The greatest difficulty that was experienced was due to the accumulation of rime on the instruments. In low temperatures everything became covered with ice crystals, deposited from the air, which eventually grew into huge blocks. Sometimes these blocks became dislodged and fell, making it dangerous to walk along the decks. The rime collected on the thermometers, the glass bowl of the sunshine recorder, and the bearings of the anemometer, necessitating the frequent use of a brush to remove it, and sometimes effectively preventing the instruments from recording at all.

One of our worst blizzards occurred on August 1, 1915, which was, for the ship, the beginning of the end. It lasted for four days, with cloudy and overcast weather for the three following days, and from that time onwards we enjoyed very little sun.

The weather that we experienced on Elephant Island can only be described as appalling. Situated as we were at the mouth of a gully, down which a huge glacier was slowly moving, with the open sea in front and to the left, and towering, snow-covered mountains on our right, the air was hardly ever free from snow drift, and the winds increased to terrific violence through being forced over the glacier and through the narrow gully. Huge blocks of ice were hurled about like pebbles, and cases of clothing and cooking utensils were whisked out of our hands and carried away to sea. For the first fortnight after our landing there, the gale blew, at times, at over one hundred miles an hour. Fortunately it never again quite reached that intensity, but on several occasions violent squalls made us very fearful for the safety of our hut. The island was almost continuously covered with a pall of fog and snow, clear weather obtaining occasionally when pack ice surrounded us. Fortunately a series of southwesterly gales had blown all the ice away to the northeast two days before the rescue ship arrived, leaving a comparatively clear sea for her to approach the island.

Being one solitary moving station in the vast expanse of the Weddell Sea, with no knowledge of what was happening anywhere around us, forecasting was very difficult and at times impossible. Great assistance in this direction was afforded by copies of Mr. R. C. Mossmann’s researches and papers on Antarctic meteorology, which he kindly supplied to us.

I have tried to make this very brief account of the meteorological side of the Expedition rather more “popular” than scientific, since the publication and scientific discussion of the observations will be carried out elsewhere; but if, while showing the difficulties under which we had to work, it emphasizes the value of Antarctic Expeditions from a purely utilitarian point of view, and the need for further continuous research into the conditions obtaining in the immediate neighborhood of the Pole, it will have achieved its object.

Owing to the continued drift of the ship with the ice, the program of physical observations originally made out had to be considerably modified. It had been intended to set up recording magnetic instruments at the base, and to take a continuous series of records throughout the whole period of residence there, absolute measurements of the earth’s horizontal magnetic force, of the dip and declination being taken at frequent intervals for purposes of calibration. With the ice continually drifting, and the possibility of the floe cracking at any time, it proved impracticable to set up the recording instruments, and the magnetic observations were confined to a series of absolute measurements taken whenever opportunity occurred. These measurements, owing to the drift of the ship, extend over a considerable distance, and give a chain of values along a line stretching roughly from 77º S. lat. to 69º S. lat. This is not the place to give the actual results; it is quite enough to state that, as might have been expected from the position of the magnetic pole, the values obtained correspond to a comparatively low magnetic latitude, the value of the dip ranging from 63º to 68º.

So far as possible, continuous records of the electric potential gradient in the atmosphere were taken, a form of quadrant electrometer with a boom and ink recording, made by the Cambridge Scientific Instrument Company, being employed. Here again, the somewhat peculiar conditions made work difficult, as the instrument was very susceptible to small changes of level, such as occurred from time to time owing to the pressure of the ice on the ship. An ionium collector, for which the radioactive material was kindly supplied by Mr. F. H. Glew, was used. The chief difficulty to contend with was the constant formation of thick deposits of rime, which either grew over the insulation and spoiled it, or covered up the collector so that it could no longer act. Nevertheless, a considerable number of good records were obtained, which have not yet been properly worked out.

Conditions during the Expedition were very favorable for observations on the physical properties and natural history of sea ice, and a considerable number of results were obtained, which are, however, discussed elsewhere, mention of them being made here since they really come under the heading of physics.

In addition to these main lines of work, many observations of a miscellaneous character were made, including those on the occurrence and nature of parhelia or “mock suns,” which were very common, and generally finely developed, and observations of the auroral displays, which were few and rather poor owing to the comparatively low magnetic latitude. Since most of the observations made are of little value without a knowledge of the place where they were made, and since a very complete set of soundings were also taken, the daily determination of the ship’s position was a matter of some importance. The drift of the ship throws considerable light on at least one geographical problem, that of the existence of Morrell Land. The remainder of this appendix will therefore be devoted to a discussion of the methods used to determine the position of the ship from day to day.

The latitude and longitude were determined astronomically every day when the sun or stars were visible, the position thus determined serving as the fixed points between which the position on days when the sky was overcast could be interpreted by the process known as “dead reckoning,” that is to say, by estimating the speed and course of the ship, taking into account the various causes affecting it. The sky was often overcast for several days at a stretch, and it was worthwhile to take a certain amount of care in the matter. Captain Worsley constructed an apparatus which gave a good idea of the direction of drift at any time. This consisted of an iron rod, which passed through an iron tube, frozen vertically into the ice, into the water below. At the lower end of the rod, in the water, was a vane. The rod being free to turn, the vane took up the direction of the current, the direction being shown by an indicator attached to the top of the rod. The direction shown depended, of course, on the drift of the ice relative to the water, and did not take into account any actual current which may have been carrying the ice with it, but the true current seems never to have been large, and the direction of the vane probably gave fairly accurately the direction of the drift of the ice. No exact idea of the rate of drift could be obtained from the apparatus, although one could get an estimate of it by displacing the vane from its position of rest and noticing how quickly it returned to it, the speed of return being greater the more rapid the drift. Another means of estimating the speed and direction of the drift was from the trend of the wire when a sounding was being taken. The rate and direction of drift appeared to depend almost entirely on the wind velocity and direction at the time. If any true current effect existed, it is not obvious from a rough comparison of the drift with the prevailing wind, but a closer investigation of the figures may show some outstanding effect due to current.
¹
The drift was always to the left of the actual wind direction. This effect is due to the rotation of the earth, a corresponding deviation to the right of the wind direction being noted by Nansen during the drift of the
Fram.
A change in the direction of the wind was often preceded by some hours by a change in the reading of the drift vane. This is no doubt due to the ice to windward being set in motion, the resulting disturbance traveling through the ice more rapidly than the approaching wind.