Survey 21 Apr 2009 Increased growth in Antarctic sea ice during the past 30
years is a result of changing weather patterns caused by the ozone hole
according to new research published this week (Thurs 23 April 2009).
Reporting in the journal Geophysical Research Letters scientists from British
Antarctic Survey (BAS) and NASA say that while there has been a dramatic loss of
Arctic sea ice, Antarctic sea ice has increased by a small amount as a result of
the ozone hole delaying the impact of greenhouse gas increases on the climate of
Sea ice plays a key role in the global environment – reflecting heat from the
sun and providing a habitat for marine life. At both poles sea ice cover is at
its minimum during summer. However, during the winter freeze in Antarctica this
ice cover expands to an area roughly twice the size of Europe. Ranging in
thickness from less than a metre to several metres, the ice insulates the warm
ocean from the frigid atmosphere above. Satellite images show that since the
1970s the extent of Antarctic sea ice has increased at a rate of 100,000 square
kilometres a decade.
The new research helps explain why observed changes in the amount of sea-ice
cover are so different in both polar regions.
Lead author Professor John Turner of BAS says,“Our results show the complexity
of climate change across the Earth. While there is increasing evidence that the
loss of sea ice in the Arctic has occurred due to human activity, in the
Antarctic human influence through the ozone hole has had the reverse effect and
resulted in more ice. Although the ozone hole is in many ways holding back the
effects of greenhouse gas increases on the Antarctic, this will not last, as we
expect ozone levels to recover by the end of the 21st Century. By then there is
likely to be around one third less Antarctic sea ice.”
Using satellite images of sea ice and computer models the scientists discovered
that the ozone hole has strengthened surface winds around Antarctica and
deepened the storms in the South Pacific area of the Southern Ocean that
surrounds the continent. This resulted in greater flow of cold air over the Ross
Sea (West Antarctica) leading to more ice production in this region.
The satellite data reveal the variation in sea ice cover around the entire
Antarctic continent. Whilst there has been a small increase of sea ice during
the autumn around the coast of East Antarctica, the largest changes are observed
in West Antarctica. Sea ice has been lost to the west of the Antarctic Peninsula
– a region that has warmed by almost 3ºC in the past 50 years. Further west sea
ice cover over the Ross Sea has increased.
Turner continues,“Understanding how polar sea ice responds to global change –
whether human induced or as part of a natural process – is really important if
we are to make accurate predictions about the Earth’s future climate. This new
research helps us solve some of the puzzle of why sea-ice is shrinking is some
areas and growing in others.”