South: The Story of Shackleton's Last Expedition, 1914-1917
W. S. Bruce, “Polar Exploration” in Home University Library, c. 1911,
pp. 54–71.
Reference should also be made to the annual publication of the Danish
Meteorological Institute showing the Arctic ice conditions of the
previous summer. This is published in both Danish and English, so that
the terms used there are bound to have a very wide acceptance; it is
hoped, therefore, that they may be the means of preventing the
Antarctic terminology following a different line of evolution; for but
seldom is a seaman found nowadays who knows both Polar regions. On the
Danish charts six different kinds of sea-ice are marked—namely,
unbroken polar ice; land-floe; great ice-fields; tight pack-ice; open
ice; bay-ice and brash. With the exception of bay-ice, which is more
generally known as young ice, all these terms pass current in the
Antarctic.
_Slush_ or _Sludge_. The initial stages in the freezing of sea-water,
when its consistency becomes gluey or soupy. The term is also used (but
not commonly) for brash-ice still further broken down.
_Pancake-ice_. Small circular floes with raised rims; due to the
break-up in a gently ruffled sea of the newly formed ice into pieces
which strike against each other, and so form turned-up edges.
_Young Ice_. Applied to all unhummocked ice up to about a foot in
thickness. Owing to the fibrous or platy structure, the floes crack
easily, and where the ice is not over thick a ship under steam cuts a
passage without much difficulty. Young ice may originate from the
coalescence of “pancakes,” where the water is slightly ruffled or else
be a sheet of “black ice,” covered maybe with “ice-flowers,” formed by
the freezing of a smooth sheet of sea-water.
In the Arctic it has been the custom to call this form of ice
“bay-ice”; in the Antarctic, however, the latter term is wrongly used
for land-floes (fast-ice, etc.), and has been so misapplied
consistently for fifteen years. The term bay-ice should possibly,
therefore, be dropped altogether, especially since, even in the Arctic,
its meaning is not altogether a rigid one, as it may denote firstly the
gluey “slush,” which forms when sea-water freezes, and secondly the
firm level sheet ultimately produced.
_Land floes_. Heavy but not necessarily hummocked ice, with generally a
deep snow covering, which has remained held up in the position of
growth by the enclosing nature of some feature of the coast, or by
grounded bergs throughout the summer season when most of the ice breaks
out. Its thickness is, therefore, above the average. Has been called at
various times “fast-ice,” “coast-ice,” “land-ice,” “bay-ice” by
Shackleton and David and the Charcot Expedition; and possibly what
Drygalski calls _Schelfeis_ is not very different.
_Floe_. An area of ice, level or hummocked, whose limits are within
sight. Includes all sizes between brash on the one hand and fields on
the other. “Light-floes” are between one and two feet in thickness
(anything thinner being “young-ice”). Those exceeding two feet in
thickness are termed “heavy floes,” being generally hummocked, and in
the Antarctic, at any rate, covered by fairly deep snow.
_Field_. A sheet of ice of such extent that its limits cannot be seen
from the masthead.
_Hummocking_. Includes all the processes of pressure formation whereby
level young ice becomes broken up and built up into
_Hummocky Floes_. The most suitable term for what has also been called
“old pack” and “screwed pack” by David and _Scholleneis_ by German
writers. In contrast to young ice, the structure is no longer fibrous,
but becomes spotted or bubbly, a certain percentage of salt drains
away, and the ice becomes almost translucent.
_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 derive_.
_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
colour, 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.
METEOROLOGY
By L. D. A. HUSSEY, B.Sc., (Lond.), Capt. R.G.A.
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
meagre, 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 string and swung round, 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 per cent. of the observations recording a
clear blue sky, 71 per cent. being completely overcast.
The percentage of clear sky increased steadily up till June and July,
these months showing respectively 42 per cent. and 45.7 per cent. In
August 40 per cent. of the observations were clear sky, while September
showed a sudden drop to 27 per cent. October weather was much the same,
and November was practically overcast the whole time, clear sky showing
at only 8 per cent. of the observations. In December the sky was
completely overcast for nearly 90 per cent. of the time.
Temperatures on the whole were fairly high, though a sudden unexpected
drop in February, after a series of heavy north-easterly 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
–35° Fahr., _i.e._ 67° 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 30°, _i.e._ 2° _below_ freezing, is
considered unbearably hot.