ANTARCTIC MELT WILL DOUBLE SEA LEVEL RISE PREDICTED BY IPCC IN 2007

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1 december 2009

Antarctic shielded by ozone hole, say scientists

By Fiona Harvey in London, Financial Times, December 1 2009

Antarctica has been protected from the most damaging effects of climate change by the impact of one of the worst environmental disasters of the 20th century, the hole in the ozone layer, research published today will reveal.

However, the study has also found that increased melting of some parts of the ice cap around the south pole will cause sea levels to rise much higher than previously expected.

John Turner, of the British Antarctic Survey, and lead editor of the work, said: "The most astonishing evidence is the way that one man-made environmental impact - the ozone hole - has shielded most of Antarctica from another - global warming."

For years, climate change scientists have been puzzling over why most of the Antarctic has shown relatively little warming, and why in some areas the ice cover has, in fact, been increasing.

The failure of the Antarctic to melt across most of its extent - in sharp contrast to the Arctic, where the decline of sea ice and the melting of Greenland's glaciers have been well-documented - has been held up by climate change sceptics as evidence of how global warming is not that serious.

But after drawing on several years of research, experts from the international Scientific Committee on Antarctic Research, a group made up of 100 leading scientists from 13 countries, now say the hole in the ozone layer has changed south polar weather systems.

Westerly winds over the Southern Ocean have, they say, intensified by about 15 per cent, "isolating Antarctica from the warming elsewhere on the planet".

As a result, during the past 30 years there has been little change in surface temperature over much of the vast continent, though west Antarctica has warmed somewhat.

When the ozone layer closes up - which it is doing, as the ozonedepleting chemicals that caused it are phased out - temperatures are expected to rise across most of the continent by only about 3°C, which will not be enough to melt the main ice sheet.

However, in parts of the ice cap that rest on the seabed rather than on a land mass, the warming sea is expected to accelerate the melting of the ice from below.

The melting of those parts of the Antarctic, along with glaciers moving faster to the sea, will be enough to raise sea levels by 1.4m by 2100, the scientists suggested yesterday.

This is a large increase on the estimate of sea level rises of 59cm suggested by the United Nations' Intergovernmental Panel on Climate Change in 2007, which failed to take account of the dynamics of ice at the south pole.

[From the website of the Scientific Committee on Antarctic Research, source of the report referred to above

Antarctic Climate Change and the Environment

This review draws together important information from different scientific disciplines (such as meteorology, glaciology and biology) and therefore different aspects of the global climate system.
* Key findings from the review are highlighted in 85 key points, which you can see in full at:
http://www.antarctica.ac.uk/met/SCAR_ssg_ps/ACCE.htm

A summary of the report’s findings are detailed in the following 10 key points:

1. Hole in ozone layer has shielded most of Antarctica from global warming.

The ozone hole has delayed the impact of greenhouse gas increases on the climate of the continent. Consequently south polar winds (the polar vortex), have intensified and affected Antarctic weather patterns. Westerly winds over the Southern Ocean that surrounds Antarctica have increased by around 15%. The stronger winds have effectively isolated Antarctica from the warming elsewhere on the planet. As a result during the past 30 years there has been little change in surface temperature over much of the vast Antarctic continent, although West Antarctica has warmed slightly. An important
exception is the eastern coast of the Antarctic Peninsula, which has seen rapid summer warming. This warming is caused by stronger westerly winds bringing warm, wet air into the region from the ocean.

2. Warming of the Southern Ocean will cause changes in Antarctic ecosystem.

The largest ocean current on Earth (the Antarctic Circumpolar Current) has warmed faster than the global ocean as a whole. The Southern Ocean is one of the major sinks of atmospheric CO2, but increasing westerly winds have affected the ocean’s ability to absorb CO2 by causing the upwelling of CO2 rich water. If temperatures continue to rise ‘alien’ species may migrate into the region, competing
with and replacing original Antarctic inhabitants. Key species in the food chain like planktonic snails could suffer from ocean acidification. Changes in the food regime are likely to decrease the rich Antarctic seabed biodiversity.

3. Rapid increase in plant communities across Antarctic Peninsula.

Rapid warming has been seen along the western Antarctic Peninsula, along with a switch from snowfall to rain during summer, resulting in expansion of plant, animal and microbial communities in newly available land. Humans have also inadvertently introduced ‘alien’ organisms such as grasses,flies and bacteria.

4. Rapid ice loss in parts of the Antarctic.

The West Antarctic Ice Sheet has significantly thinned particularly around the Amundsen Sea Embayment as a result of warmer ocean temperatures. Regional warming caused by intensification of the westerly winds (due to the ozone hole) is melting ice shelves along the eastern Antarctic Peninsula (e.g. Larsen B Ice Shelf). Overall, 90% of the Peninsula’s glaciers have retreated in recent decades. However, the bulk of the Antarctic ice sheet has shown little change.

5. 10% increase in sea ice around the Antarctic.

Since 1980 there has been a 10% increase in Antarctic sea ice extent, particularly in the Ross Sea region, as a result of the stronger winds around the continent (due to the ozone hole). In contrast, regional sea ice has decreased west of the Antarctic Peninsula due to changes in local atmospheric circulation and this has also been linked with the very rapid warming seen over land on the west coast of the Peninsula.

6. Carbon dioxide levels increasing at fastest pace in 800,000 years.

Atmospheric concentrations of CO2 and CH4 are at higher levels than experienced in the last 800,000 years and are increasing at rates unlikely to have been seen in the (geologically) recent past.
Antarctica was warmer in the last interglacial (130,000 years ago) and sea levels were higher, but the contribution of West Antarctica to that rise is currently unknown. Small-scale climate variability over the last 11,000 years has caused rapid ice loss, shifts in ocean and atmospheric circulation and enhanced biological production, showing that Antarctica is highly sensitive to even minor climate changes. Studies of sediments under recently lost ice shelves suggest ice shelf loss in some regions is unprecedented during this time scale.

7. Sea ice loss directly affecting krill levels and penguin colonisation.

Loss of sea ice west of the Antarctic Peninsula has caused changes in algal growth. This loss of sea ice has also caused a shift from large to smaller species. Stocks of krill have declined significantly. In some areas Adélie penguin populations have declined due to reduced sea ice and prey species (on the northern Antarctic Peninsula), but they have remained stable or increased elsewhere (Ross Sea and East Antarctica). Historical exploitation of seals and whales has changed the ecosystem, reducing scientists’ ability to fully understand the impacts of climate change on krill and other species.

8. Antarctica predicted to warm by around 3°C over this century.

Over this century the ozone hole is expected to heal, allowing the full effects of greenhouse gas increases to be felt across the Antarctic. Models suggest that the net effect will be continued slow strengthening of winds across the Southern Ocean, while sea ice will decrease by a third, resulting in increased phytoplankton productivity. The predicted warming of about 3°C across the continent is not enough to melt the main ice sheet and an increase in snowfall there should offset sea level rise by a few centimetres.

9. West Antarctic ice loss could contribute to 1.4 m sea level rise.

Loss of ice from the West Antarctic ice sheet is likely to contribute some tens of centimetres to global sea level by 2100. This will contribute to a projected total sea level rise of up to 1.4 metres (and
possibly higher) by 2100.

10. Improved modelling of polar processes required for accurate predictions.

Climate variability in the Polar Regions is larger than in other parts of the world, yet these remote regions are sparsely sampled. These areas need to be monitored in much greater detail in order to detect change, to improve understanding of the processes at work, and to distinguish between natural climate variability and variability caused by human influences. A detailed understanding of past
climate is also crucial for understanding this distinction, as is a significant refinement of currently crude climate models.

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Scientific Committee on Antarctic Research (SCAR) is the main body dealing with the international co-ordination of scientific research in Antarctica and the Southern Ocean. Formed with 12 member countries in 1958 to continue activities begun during the International Geophysical Year of 1957 – 58, it is an interdisciplinary committee of the International Council for Science (ICSU) and now has 35 Member countries. SCAR played a leading role in the recently completed International Polar Year (2007 – 2008).

British Antarctic Survey (BAS), a component of the Natural Environment Research Council, delivers
world-leading interdisciplinary research in the Polar Regions. Its skilled science and support staff based in Cambridge, Antarctica and the Arctic, work together to deliver research that underpins a
productive economy and contributes to a sustainable world. Its numerous national and international collaborations, leadership role in Antarctic affairs and excellent infrastructure help ensure that the UK maintains a world leading position. BAS has over 450 staff and operates five research stations, two Royal Research Ships and five aircraft in and around Antarctica.


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