Antarctic snow may hide climate shock

[Colin McHenry <cmchenry@westserv.net.au>]

The latest data from an Antarctic ice core project  (involving a 
colleague here at NU) is in this week's Science.

Story is here:
http://www.abc.net.au/science/news/stories/s1710851.htm

Pasted below (for those of you without fast internet / who use off-line 
access to this list ;-) )

Colin
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A new study that shows Antarctic snowfalls have changed little in 50 
years, despite global warming, could be evidence that the worst is yet 
to come, says one of the authors.

A study published today in the journal Science reports that, contrary to 
expectations, snowfall in Antarctica has not increased over the past 50 
years.

This contradicts the predictions of most climate models that are based 
on the assumption that warming air can carry more moisture and produce 
greater snowfalls at the poles.

"The models predict that Antarctic snowfall should be increasing with a 
warming atmosphere," says Australian team member and palaeoclimatologist 
Dr Ian Goodwin, of the University of Newcastle.

Goodwin doesn't challenge this basic climate physics. But says the 
recent evidence supports the idea, not recognised in climate models, 
that there is a lag between global warming and Antarctica's response to it.

The reason is that Antarctica and the southern hemisphere are surrounded 
by large oceans that take a long time to heat and therefore act as a 
buffer to climate change.

Recent evidence suggests the lag time could be up to 60 years, says Goodwin.

"We can be relatively complacent about the effects of climate change in 
the Southern Hemisphere because we haven't seen dramatic changes," he says.

"But the frightening thing I think is that we are not yet seeing the 
full impact of global warming in the southern hemisphere. But it's just 
around the corner."

Natural cycles

Goodwin and colleagues published a study in 1991 that showed an increase 
in snowfall in east Antarctica.

But, the new study shows that since then, the amount of snow falling in 
that area has decreased.

Goodwin and colleagues used direct measurement of snowfall and more than 
50 ice cores to reconstruct annual snowfall over the past 50 years.

He says the study demonstrates a previously unknown natural climate 
cycle, affecting the whole of Antarctica.

"On one side of Antarctica in some decades we see an increase in 
accumulation [of snow] and on the other side of Antarctica we see a 
decrease and so it balances out to zero net gain," he says.

Goodwin says this variability is so great it could mask any changes due 
to global warming.

But, he says, it could only be a matter of time before the natural cycle 
becomes dwarfed by the changes brought about by global warming.

And this is where he says the lag time becomes important.

"If we were to rewrite this paper in say 10 years time the likelihood is 
that we will be actually be writing a paper that says 'significant 
change in Antarctic snowfall over the last 10 to 15 years'," says Goodwin.

"In all likelihood we're about to see, in the next couple of decades, a 
very large response to global warming in Antarctic and Southern Ocean 
regions."

Goodwin says that the new research should now feed into climate models 
and make them more accurate.




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Colin McHenry
School of Environmental and Life Sciences (Geology)
University of Newcastle
Callaghan NSW 2308
Australia
Tel: +61 2 4921 5404
Fax: + 61 2 4921 6925

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