[Aqualist] Media Release: Snowy Mountains much colder and drier at
end of the last Ice Age
simon.haberle at anu.edu.au
Wed Dec 10 15:44:09 EST 2003
Media release from recent AAA Conference at Jindabyne, NSW
Snowy Mountains much colder and drier at end of the last Ice Age
Recent scientific studies have discovered that temperatures in the Snowy
Mountains about 20 000 years ago were 8 to 9 degrees colder and conditions
in Australia were also probably drier than today in most parts of Australia.
According to Professor John Chappell of the Australian National University
s Research School of Earth Sciences, scientists previously believed that
the temperature in Australia at the end of the last Ice Age was around 5
degrees colder than it is today.
Until recently we summarised the Australian situation as being about 5
degrees and somewhat drier for a few thousand years. New evidence indicates
that we underestimated the change , Professor Chappell said.
Ice sheets on the northern continents were at their maximum extent 20 000
years ago the Last Glacial Maximum (LGM) and conditions were colder and
drier than today. This poses the question of how humans adapted in order to
live through these harsher conditions. To begin to consider this, we must
first estimate how much harsher conditions were then, compared with today.
The northern ice sheets we now know to have been close to their maximum
size from about 28 000 to 18 000 years ago an interval of about 10 000
years. Recent studies of glacial and ice-related landforms in the Snowy
Mountains and Tasmania indicate that temperatures in the LGM in
south-eastern Australia were 8 to 9 degrees colder than today. These
discoveries have prompted a re-evaluation of the LGM and the conditions
that preceded it.
There is little doubt that arid conditions extended across much of the
Australian interior at the LGM. Dune fields then covered about 60 per cent
of the continent, and were more mobile, and appear to have been active in
areas now used for agriculture, particularly in Western Australia. The
duration of the period of maximum aridity is not well established and may
have been no longer than a few thousand years to judge from windblown dust
found in sediments in the Tasman Sea.
Similarly, the most intensely cold episode, which led to maximum aridity,
also extended for little more than a few thousand years, from about 24 000
years to 19 000 years ago.
However, to characterise the LGM simply as having been arid and very much
colder gives a false impression. Climate is more than a matter of rainfall
or temperature: evaporation, groundwater and surface runoff affect the
landscape, together with its vegetation and fauna.
Also, paradoxically, there was more water in localised parts of the
Australian landscape at the end of the last Ice Age than there is today.
For example, Lake George near Canberra, which is now dry, was 12 metres
deep and larger than it has ever been since Europeans arrived in the area
in the 1800s.
The context of human activity about 20 000 years ago in Australia was not
only much colder, it was also very different in other ways. It was a land
of even greater contrasts than it is today. The great desert tracts may
have been even harsher than now, but the alternation of floods and droughts
that bedevils our climate today, appears not to have been as extreme as it
is today. Human subsistence in wetland, riverine and better-watered upland
areas may have been more dependable then as the climate was less variable,
even though it was much colder.
The LGM was but the last in a procession of dramatic climate changes that
affected the entire world throughout the last few million years. It is
salutary to observe that human impacts on the biota, measured in terms of
extinctions and land degradation, exceed the effects of the climatic
impacts, throughout this long history of repeated changes.
Professor Chappell s comments were made during his keynote speech at the
25th annual conference of the Australian Archaeology Association held at
Jindabyne from 3 to 7 December 2003. The first conference of the
association was held at Kioloa, New South Wales in 1978.
More than 200 delegates from Australia and overseas attended the conference
at Perisher Blue s Station Resort just out of Jindabyne. During their stay
many delegates took the opportunity to visit the Kosciuszko National Park
to view significant Aboriginal and geological sites in the area.
John Chappell, (02) 6125 8113
Tim Winkler, ANU Marketing and Communications (02) 6125 5001
Jane Morrison, AAA Conference Media Officer (02) 6294 0146 Mobile 0414 279 571
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Ausarch-l at anu.edu.au
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