Ladda ner årsbok 2008 (6,5 MB) - Polarforskningssekretariatet

Figure 4
Stefan Gunnarsson shifting gearbox
on the TL-4. Photo: Per Holmlund
20
and 900 metre deep. Although it is now
covered by 4 km of ice, it is believed that
Lake Vostok has been in existence since the
time when it had an open lake surface more
than 20 million years ago. The lakes we were
examining with radar were approximately 20
km wide and covered by 3 km of ice.
Studying ice layers
The ice layers as seen in radar registrations are
most interesting features. They exist from the
surface down to a depth of approximately 1.5–2
km, corresponding to the ice formed after the
termination of the last Ice Age ten thousand
years ago. The relative pattern-consistency of
internal layers with depth indicates whether
or not the ice dynamics have been stable over
time, which appears to be the case.
The snow layering was surveyed down
to a depth of 20 metre, which corresponds
to the snow accumulation over the past two
FoRSKARRAPPoRTER CRUISE REPoRTS SWEDARP 2007/08
centuries. One important objective for the
snow radar programme was to link these
ground truth data to satellite images in order
to extend the data spatially. The ultimate
goal is to find the toll for surveying snow
accumulation on Antarctica with satellites, a
goal that was shared by our Japanese colleagues
working on the relation between properties of
snow and radio wave scatter at high frequencies.
The chemistry of the snow describes the
air mass from which the precipitation once
originated and furthermore reflects how
pollutants are spread throughout the world.
Although Antarctica is the cleanest continent
in the world, human activities can be traced
even there. The nuclear bomb tests made in
the atmosphere in the early fifties and the
early sixties resulted in fall out being spread
all over the world, which phenomenon is
commonly used for dating horizons all over
Antarctica.