1 December 2009

Major sea level rise likely as Antarctic ice melts

By Richard Black, Environment correspondent, BBC News, December 1, 2009 The Southern Ocean is the world's most important feeding ground for whales Sea levels are likely to rise by about 1.4 m (4.5 ft.) globally by 2100 as polar ice melts, according to a major review of climate change in Antarctica. Conducted by the Scientific Committee on Antarctic Research (SCAR), it says that warming seas are accelerating melting in the west of the continent. Ozone loss has cooled the region, it says, shielding it from global warming. Rising temperatures in the Antarctic Peninsula are making life suitable for invasive species on land and sea. The report - Antarctic Climate Change and the Environment - was written using contributions from 100 leading scientists in various disciplines, and reviewed by a further 200. Rising seas: A tale of two cities SCAR's executive director Dr Colin Summerhayes said it painted a picture of "the creeping global catastrophe that we face." "The temperature of the air is increasing, the temperature of the ocean is increasing, sea levels are rising - and the Sun appears to have very little influence on what we see," he said. SCAR's report comes 50 years to the day after the Antarctic Treaty, the international agreement regulating use of the territory, was opened for signing, and a week before the opening of the potentially seminal UN climate summit in Copenhagen. High rise Two years ago, the Intergovernmental Panel on Climate Change (IPCC) projected that the global average sea level would probably rise by 28-43 cm (11-16 in.) by the end of the century. But it acknowledged this figure was almost certainly too low, because it was impossible to model "ice dynamics" - the acceleration in ice melting projected to occur as air and water temperatures rise. Launching the SCAR report in London, lead editor John Turner from the British Antarctic Survey (BAS) suggested that observations on the ground had changed that picture, especially in parts of the West Antarctic ice sheet. "Warmer water is getting under the edges of the West Antarctic ice sheet and accelerating the flow of ice into the ocean," he said. Glaciers: If the world's mountain glaciers and icecaps melt, sea levels will rise by an estimated 0.5 m Thermal expansion: The expansion of warming oceans was the main factor contributing to sea level rise, in the 20th Century, and currently accounts for more than half of the observed rise in sea levels Ice sheets: These vast reserves contain billions of tonnes of frozen water - if the largest of them (the East Antarctic ice sheet) melts, the global sea level will rise by an estimated 64 m By the end of the century, he said, the sheet will probably have lost enough ice alone to raise sea levels globally by "tens of centimetres." The remainder of the projected rise would come from melting of the Greenland cap, melting of mountain glaciers in the Himalayas and Andes, and the expansion of seawater as it warms. A number of research teams have come up with similar projections. But this is the first time that an international body such as SCAR has endorsed the likelihood that sea levels will rise enough to threaten some of the world's biggest cities by the end of the century. Cold store The Antarctic Peninsula - the strip of land that points towards the southern tip of South America - has warmed by about 3 °C over the last 50 years, the fastest rise seen anywhere in the southern hemisphere, according to the report. But the rest of the continent has remained largely immune from the global trend of rising temperatures. ANTARCTIC CLIMATE CHANGE Full report from the Scientific Committee on Antarctic Research [20MB] Most computers will open this document automatically, but you may need Adobe Reader Download the reader here Indeed, the continent's largest portion, East Antarctica, appears to have cooled, bringing a 10% increase in the sea ice extent since 1980. This report backs the theory that it has bucked the global trend largely because of ozone depletion - the chemical havoc wrought over 30 years by chlorofluorocarbons (CFCs) and other agents in the stratosphere above the polar region. "We used to have a big blanket of ozone, and when we took it away we saw a cooling," said Professor Turner. "The Antarctic has been shielded from the impacts of global warming." But, the report concludes, that will not last forever. The ozone hole is expected to repair itself in about 50 years, now that the Montreal Protocol has curbed the use of ozone-destroying substances. As it does so, the SCAR team predicts that greenhouse warming will come to dominate the temperature change across Antarctica, as in other parts of the planet. Doubling of greenhouse gas concentrations in the atmosphere would warm the continent by 3-4 °C, it says. The majority of Antarctica is so cold that a rise of this magnitude in air temperature would have little impact. But more warming of the oceans would speed ice loss still further, the report concludes. On the basis of declines seen around the Antarctic Peninsula, it would also be expected to bring significant reductions in the abundance of krill, a key foodstuff for baleen whales and other animals. Among humankind, the frozen continent was once a preserve of explorers and scientists. But now, about 30,000 tourists a year visit, some setting foot on outlying parts of the peninsula. This increased human traffic, plus the warming on land and sea, are going to change the region's ecology, according to Julian Gutt, allowing organisms to enter and survive that were previously excluded through climate or simple geography. "A good candidate is the stone crab (aka king crab) such as those found throughout Norwegian waters - they're more than a metre across from toe to toe. "There are hints of it hopping across from South America - and that could completely change the ecosystem on the sea floor," said the Alfred Wegener Institute researcher. About one third of one percent of Antarctica's land surface is ice-free; but already, non-native species are competing with native mosses for this meagre resource, Dr Gutt noted. Richard.Black-INTERNET@bbc.co.uk

Link:  http://news.bbc.co.uk/2/hi/science/nature/8387137.stm

First comprehensive review of the state of Antarctica's climate

Antarctic Climate Change and the Environment

The first comprehensive review of the state of Antarctica's climate and its relationship to the global climate system is published this week (Tuesday 1 December 2009) by the Scientific Committee on Antarctic Research (SCAR). The review - Antarctic Climate Change and the Environment – presents the latest research from the icy continent, identifies areas for future scientific research, and addresses the urgent questions that policy makers have about Antarctic melting, sea-level rise and biodiversity.

Based on the latest evidence* from 100 world-leading scientists from 13 countries, the review focuses on the impact and consequences of rapid warming of the Antarctic Peninsula and the Southern Ocean; rapid ice loss in parts of Antarctica and the increase in sea ice around the continent; the impact of climate change on Antarctica's plants and animals; the unprecedented increase in carbon dioxide levels; the connections between human-induced global change and natural variability; and the extraordinary finding that the ozone hole has shielded most of Antarctica from global warming.

Dr. Colin Summerhayes, Executive Director of the Scientific Committee on Antarctic Research said, "Antarctica is an unrivalled source of information about our planet. This review describes what we know now and illustrates how human activity is driving rapid climate change. By integrating this multidisciplinary evidence into a single source we will help scientists and policy makers understand the distinction between environmental changes linked to the Earth's natural cycles, and those that are human induced. The work is particularly important because it puts Antarctic climate change into context and reveals the impact on the rest of the planet."

Professor John Turner of British Antarctic Survey is the lead editor of the review. He said, "For me 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. Understanding the complexities surrounding these issues is a challenge for scientists – and communicating these in a meaningful way to society and to policymakers is essential. There is no doubt that our world is changing and human activity is accelerating global change. This review is a major step forward in making sure that the latest and best evidence is available in one place. It sets the scene for future Antarctic Research and provides the knowledge that we all need to help us live with environmental change."

Notes for editors:
Stunning broadcast-quality footage and stills of Antarctica, as well as location maps are available from the British Antarctic Survey Press Office.

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.

The 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 1957–1958, 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.

Link:  http://www.eurekalert.org/pub_releases/2009-11/bas-fcr113009.php

Geophysical Research Letters, 36 (2009) L15705; doi: 10.1029/2009GL038671.

Ozone hole and Southern Hemisphere climate change

Seok-Woo Son (Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, Canada), Neil F. Tandon (Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, U.S.A.), Lorenzo M. Polvani (Department of Applied Physics and Applied Mathematics and Department of Earth and Environmental Sciences, Columbia University, New York, NY, U.S.A.), and Darryn W. Waugh (Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, U.S.A.)

Abstract

Link to abstract: http://www.agu.org/pubs/crossref/2009/2009GL038671.shtml

Ozone hole has unforeseen effect on ocean carbon sink

by Kate Ravilious, NewScientist, June 26, 2009

The Southern Ocean has lost its appetite for carbon dioxide, and now it appears that the ozone hole could be to blame.

In theory, oceans should absorb more CO₂ as levels of the gas in the atmosphere rise. Measurements show that this is happening in most ocean regions, but strangely not in the Southern Ocean, where carbon absorption has flattened off. Climate models fail to reproduce this puzzling pattern.

The Southern Ocean is a major carbon sink, guzzling around 15% of CO₂ emissions. However, between 1987 and 2004, carbon uptake in the region was reduced by nearly 2.5 billion tonnes – equivalent to the amount of carbon that all the world's oceans absorb in one year.

Premature effect

To figure out what is going on, Andrew Lenton, from the University of Pierre and Marie Curie in Paris, France, and his colleagues created a coupled ocean and atmosphere climate model, to investigate carbon absorption in oceans. Crucially, they included changes in the concentration of stratospheric ozone since 1975.

By running their model with and without the ozone depletion since 1975, Lenton and his colleagues were able to show that the ozone hole is responsible for the Southern Ocean's carbon saturation.

The effect could be down to the way decreasing stratospheric ozone and rising greenhouse gases are altering the radiation balance of the Earth's atmosphere. This has been predicted to alter and strengthen the westerly winds that blow over the Southern Ocean.

"We expected this transition to a windier regime, but it has occurred much earlier than we thought, seemingly because of the ozone hole," says Lenton.

'Unexpected effect'

Stronger surface winds enhance circulation of ocean waters, encouraging carbon-rich waters to rise from the deep, limiting the capability of surface water to absorb carbon from the atmosphere. Furthermore, the higher carbon levels in surface waters make them more acidic – bad news for many forms of ocean life, such as coral and squid.

"This result illustrates how complex the chain of cause and effect can be in the Earth system. No one would ever have predicted from first principles that increasing CFCs would have the effect of decreasing uptake of ocean carbon dioxide," says Andrew Watson, from the University of East Anglia, U.K.

Journal reference: Geophysical Research Letters (DOI: 10.1029/2009GL038227)

Link to article: http://www.newscientist.com/article/dn17385-ozone-hole-has-unforeseen-effect-on-ocean-carbon-sink.html

Proceedings of the National Academy of Sciences, published online before print June 22, 2009; doi: 10.1073/pnas.0902817106

The large contribution of projected HFC emissions to future climate forcing

Link to article: http://www.pnas.org/content/early/2009/06/19/0902817106.abstract

Real Climate: Winds of Change

Geophysical Research Letters, 36, L08502; doi:10.1029/2009GL037524.

Non‐annular atmospheric circulation change induced by stratospheric ozone depletion and its role in the recent increase of Antarctic sea ice extent

John Turner (British Antarctic Survey, National Environment Research Council, Cambridge, U.K.), Josefino C. Comiso (NASA Goddard Space Flight Center, Greenbelt, MD, U.S.A.), Gareth J. Marshall, Tom A. Lachlan‐Cope, Tom Bracegirdle, Ted Maksym, Michael P. Meredith, Zhaomin Wang, and Andrew Orr (British Antarctic Survey, National Environment Research Council, Cambridge, U.K.)

BLOGGER'S NOTE: This is probably one of my most favorite subjects -- the vortices!

Why Antarctic ice is growing despite global warming

by Catherine Brahic, New Scientist, April 20, 2009

It's the southern ozone hole whatdunit. That's why Antarctic sea ice is growing while at the other pole, Arctic ice is shrinking at record rates. It seems CFCs and other ozone-depleting chemicals have given the South Pole respite from global warming.

Winds circle clockwise around Antarctica, whip off Victoria Land and create a vortex of cold storms (dark blue) off the Ross Sea, where sea ice is expanding. The vortex also draws in warm (red) air from South America, which warms the Antarctic Peninsula (Image: modified from Turner/AGU) -- Please click on the graphic to enlarge the details.

But only temporarily. According to John Turner of the British Antarctic Survey, the effect will last roughly another decade before Antarctic sea ice starts to decline as well.

Arctic sea ice is decreasing dramatically and reached a record low in 2007. But satellite images studied by Turner and his colleagues show that Antarctic sea ice is increasing in every month of the year except January. "By the end of the century we expect one third of Antarctic sea ice to disappear," says Turner. "So we're trying to understand why it's increasing now, at a time of global warming."

In a new study, Turner and colleagues show how the ozone hole has changed weather patterns around Antarctica. These changes have drawn in warm air over the Antarctic Peninsula in West Antarctica and cooled the air above East Antarctica.

The Southern Ocean is home to some of the strongest ocean winds on the planet. The region between 40° and 60° South is well-known to sailors who call it the "roaring forties" and "furious fifties."

Wind vortex

If the South Pole were smack in the middle of Antarctica, the winds would circle neatly around it in a clockwise direction. But in fact the continent is set slightly off-centre relative to the South Pole. As a result, the winds whip off Victoria Land and create a vortex over the Southern Ocean north of the Ross Sea (see blue area in figure). Turner compares this to the way wind going down a line of buildings will whip into a vortex when it comes to a corner.

The vortex generates a large area of storm activity. It also draws in warm air from South America over the Antarctic Peninsula, making this the warmest region of the continent.

By running an atmospheric computer model with and without the ozone hole, Turner and his colleagues found that the depletion of the ozone has intensified the winds of the roaring forties and furious fifties. The net result has been to draw more warm air in from Chile – which has warmed the Antarctic peninsula and caused the collapse of several ice shelves – and generate stronger cool-air storms around the Ross Sea.

Satellite data shows that sea ice has shrunk west of the Antarctic Peninsula and grown in the Ross Sea. Because the increase in sea ice extent has been greater than the reduction around the Antarctic peninsula, the net effect is that since the ozone hole appeared 30 years ago, Antarctic ice has grown. The researchers say their models suggest this is most likely a result of the ozone hole, although they cannot rule out the possibility that natural variations in sea ice extent have also played a role.

Ozone healing

"Over the next 50 to 100 years, the ozone hole will heal," says Turner. "At the same time, greenhouse gases will rise. In next decade or so we should see sea ice plateauing and then decreasing massively if greenhouse gases continue to increase."

Earlier this year, research led by Eric Steig of the University of Washington, Seattle, showed that although the Antarctic continent as a whole has warmed by 0.5 °C in the last 50 years – on a par with the global average – the figure hides strong regional differences. West Antarctica has warmed while temperatures over East Antarctica have dropped.

Accordingly, the disintegration of large ice shelves have all been in West Antarctica, the most famous example being the Larsen ice shelf. More recently, scientists have been anxiously expecting the Wilkins ice shelf to collapse as well.

Journal reference: Geophysical Research Letters (DOI: 10.1029/2009GL037524, in press).

Link to article: http://www.newscientist.com/article/dn16988-why-antarctic-ice-is-growing-despite-global-warming.html