Friday
11 August 2006 - Despite changes in global climate,
a new study shows that snowfall in Antarctica
has changed little in the past 50 years.
A paper published today in the
prestigious journal Science an international team
of 16 scientists from USA, Australia, China, Germany,
Italy, Norway and Russia reports on variations
in Antarctic snowfall since 1955.
The study shows that although
snowfall is marked by large variations across
the continent - and through time - there has been
little overall change in the past 50 years.
The research used meteorological
data to explore recent changes since around 1985.
However, other measurements, mostly from ice cores,
were required to get an accurate picture of earlier
changes in snowfall.
The snow builds up in annual
layers which can be detected as chemical changes
in ice cores drilled down through the surface.
The ice core and related snow
measurements from 16 locations across the entire
continent were combined to build up a map of snowfall
fluctuations through the five decades.
The research team, led by meteorologists
Andy Monaghan and David Bromwich from Ohio State
University, relied on several ice cores from the
Australian Antarctic programme to fill the map
regions in East Antarctica.
An Australian co-author on the
study Dr. Tas van Ommen – of the Australian Antarctic
Division and leader of the Climate History Project
at the Antarctic Climate and Ecosystems Cooperative
Research Centre - comments that the paper has
important implications for understanding how Antarctic
changes are affecting sea-level.
"Uncertainty over changes
in the amount of water locked up in the Antarctic
ice sheet is one of the greatest unknowns in predictions
of future sea level," Dr van Ommen said.
"At present, we have a
range of tantalising clues: satellite measurements
which show the ice sheet growing in places, and
thinning in others, but each of these is a short-term
snapshot of a much longer, slower drama.
"Studies like this one
that use the longer-term information trapped in
ice cores, have potential to give us the answers
we need if we are to predict future impacts."
Dr van Ommen said that the study
was also interesting because snowfall had generally
been expected to increase with a warming climate,
because warmer air can hold more moisture, but
such a trend was not seen in the past 50 years.
"However, the pattern of
warming in the Antarctic is complicated, both
across the continent and through the atmosphere,
so the absence of a clear impact on snowfall may
not be surprising."
The paper suggests that changes
in circulation patterns that bring moisture to
the continent – essentially the patterns of storms
– could act to reduce snowfall even in a warming
atmosphere.
If this were to occur, the total
water stored on the Antarctic continent would
not increase as is generally expected, and rates
of sea-level rise would be larger than otherwise
predicted.
Paper title:
Insignificant Change in Antarctic Snowfall Since
the International Geophysical Year
Authors:
Monaghan, A., J., Bromwich, D. H., Fogt, R. L.,
Wang, S.-H., Mayewski, P. A., Dixon, D. A., Ekaykin,
A., Frezzotti, M., Goodwin, I. D., Isaksson, E.,
Kaspari, S. D., Morgan, V. I., Oerter, H., van
Ommen, T. D., van der Veen, C., J. and Wen, J.
