Antarctic snowfall largely unchanged in half a century
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.
Australian Antarctic ice cores help build a map of snowfall
Insignificant Change in Antarctic Snowfall Since the International Geophysical Year
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.
Corresponding author, Andrew J Monaghan, Ohio State University
Australian contact, Dr Tas D. van Ommen, Antarctic Climate & Ecosystems CRC and Australian Antarctic Division