Antarctic sea ice declines 20pc
November 14, 2003
ANTARCTIC sea ice has decreased by about 20 per cent since the
1950s, groundbreaking Australian research has found.
A team led by Australian Antarctic Division senior ice core chemist
Mark Curran has harnessed new technology to piece together changes
to sea ice dating back to 1840.
Hailed as the first long-term evidence of sustained decline, the
study results will be published today in the latest edition of
Dr Curran said glaciologists had developed and calibrated a new tool
to measure chemical signals in ice core samples collected from the
Law Dome, near Australia's Casey station.
"What we have done is used a chemical in the ice core called Methane
Sulfonic Acid (MSA)," he said.
MSA is produced by tiny single-cell ocean plants called
"The amount of MSA in the ice core is related to the northerly
extent of the Antarctic sea ice," Dr Curran said.
"Therefore, in years where you have more sea ice, you get more
algae, and they produce more MSA."
He said while scientists used satellite observations to track sea
ice movement since the 1970s, the new method allowed a much bigger
picture of long-term change.
Dr Curran said sea ice was subject to very large decade-to-decade
"This decadal variability has hampered our knowledge of sea ice
extent from the very short satellite era," he said.
"By going back further in time, we were able to look at the sea ice
extent since 1840.
"Scientists have always predicted that the sea ice should show a
response to climate change, but we haven't been able to detect that
in the short record that we have.
"Now that we have a longer record available, we can detect that
"What we show is the first evidence of a sustained sea ice decline
since the 1950s."
He said the data showed a 20 per cent loss in sea ice since the
1950s over the region closest to the ice core.
Antarctic sea ice is integral in controlling climate stability in
the region and also provides ecosystem support.
It forms cold dense water that sinks to the bottom of the ocean and
drives global ocean circulation, which is important to the wider
Glaciologist are now analysing data from a much deeper ice core,
which goes back 1.2km and covers about 90,000 years.
"We have only just scratched the surface," Dr Curran said.
"We can go back further in time.
"We can at least start and look at the last few hundred years and
determine if the change that we see over the last 50 years is
Dr Curran described the research as a leap forward in efforts to
reconstruct past sea ice patterns.
He said although it showed a marked decline in recent years, it was
not all "doom and gloom".
"While this work indicates the Antarctic sea ice is decreasing, we
have learnt more about the past history of the ice and this work
gives us more knowledge of the climate system," Dr Curran said.
"The more knowledge we have the better equipped we are to protect
and understand the planet."
Dr Curran will present a paper on the issue next week at an
international science conference on global change in Trieste, Italy.
This is consistant with three important things. First, it is
consistant with a warmer ocean. Second, paradoxically, it is
consistant with some of Dr. Peter Doran's work showing a COLDER
Antarctica interior! Why? Because the circumpolar inducts against
cirrus, and the warmer the conducter is, the better it inducts, and a
warmer ocean will induct AGAINST heat trapping cirrus. The interior
gets colder AND drier. Third, the proxy used here is BIOLOGICAL, and
gets to yet another conductivity modultion. This modulation is
critical globally, not just because of global circulation but also
because of the earth EMF itself is driven by the impedences involved
as the global electrical circuit is varied by human activity.