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Along
the route from "King Baudouin Base - South Pole - McMurdo"
Hubert and Dansercoer will collect surface snow samples
for the analysis of stable isotopes.
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equipment required for taking observations are light
and not at all cumbersome: a mini-ice core sampler (a
titanium tube, several centimetres long and a few centimetres
in diameter) and all the little bottles for the samples,
plate and scales for the density, thermocouple, ANENA
table, magnifying glass and data tables. The camera
and spade are already part of the expedition's basic
equipment. |
It is thanks to the Belgian doctor Hubert Gallée,
who specialises in the study of atmospheric dynamics at
the Georges Lemaître Institute at the UCL (Université
Catholique de Louvain, Belgium) - and seconded for a year
to the Centre for the Study of Snow/French Meteorology -
that the Laboratory of Glaciology & Environmental Geophysics
at Grenoble (France) showed an interest in these snow samples.
The weight of the equipment to be transported (5 to 8 kg)
was designed to be compatible with the nature of this expedition.
Collecting snow samples.
The isotopic values for snow (Deuterium and Oxygen 18) represent
the perfect tool for recreating temperatures from ice core
samples. In fact, the heavy isotopic composition of snowfall
depends on water particles evaporating from the oceans and
condensing in clouds as they make their journey to the ice-caps.
Paleoclimatologists have observed, on several expeditions
carried out in Antarctica and Greenland, a practically linear
relationship linking the isotopic composition of snow and
the temperature of the site where the sample was collected.
Theoretical studies and numerical simulations confirm this
link and show that the condensation temperature is the dominant
factor which determines the isotopic value. It is then possible
to make a temperature correspond to each isotopic composition
of an ice sample.
Given the size of the polar ice-caps, and in particular
that of the Antarctic, collections of snow samples have
been few and far between up until now. The international
scientific community is currently organising itself to set
up in the longer term a project for sample collection covering
some 15 million square km in Antarctica (the ITASE Project:
International Trans-Antarctic Scientific Expedition - conducted
by Dr Paul Mayewski of the University of New Hampshire,
USA). The forthcoming project will rely on significant logistical
resources (tractors, sledges, etc.) and would aim to carry
out drilling to depths of 200 metres for the study of stable
isotopes and the physical and chemical parameters of Antarctic
snow. The information which the researchers could collect
from the samples along the entire route of the expedition
to be taken by the Belgians will help build their data base
and guide future crossings of the ITASE programme.
The snow which is collected is mixed on plastic strips
and one or two aliquots are collected directly with the
help of plastic bottles. Ideally samples are required every
50 kilometres on average, however this frequency will be
based on the needs of the expedition (nightly stops). The
project managers hope to have up to 50 collection sites
from the point of departure to the South Pole and about
30 sites from the South Pole to McMurdo. The characteristics
of samples (date, depth, geographic co-ordinates, possible
stratigraphy, comments) will be noted in the expedition
diary. Samples collected between Queen Maud Land and the
South Pole will be handed over to the station managers at
Amundsen-Scott and new flasks could be collected there for
sample collections on the journey to McMurdo.
Observations of the physical characteristics of surface
snow.
This involves obtaining data relating on the one hand to
the stratigraphy, the temperature and density of snow, and
on the other hand, the size and shape of the snowflakes
as well as the structure of the surface. This data is important
for remote detection (which remains the only method of investigating
the polar ice-caps with high spatial and temporal density
data) and for studies on changes to the snow. With the exception
of surface structure, observations must be carried out at
different levels, for example, 0, 5, 10, 20, 30, 40, 60,
100, 150 and 200 cm, and down to a depth of at least one
metre (2 metres is even better).
A series of observations is desirable on average every
150 km if possible (depending on the requirements of the
expedition) or whenever there is a clearly visible transition
(appearance or disappearance of sastrugis; sastrugis are
forms of erosion or accumulations created by the wind on
the surface of the snow. They may attain a height of some
tens of centimetres, up to one metre in extreme cases).
The time for the series of observations to be carried out
- drilling of a bore of 1 to 2 metres included - is estimated
at about 1 to 2 hours.
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