Antarctic meltdown: can we stop it in time?
By Norm Dixon
You stumble out of bed in bare feet to make that pot of coffee to start the heart, you approach the fridge and — step in a huge puddle of chilly water. Somebody didn't shut the fridge door properly. Once ice starts to melt, it is hard to stop, and it can be surprisingly destructive. This is also the case on a global scale. Some of the planet's more irresponsible house-mates have left the fridge door ajar. The consequences could be catastrophic and may take place very soon.
The concentration of greenhouse gases — primarily carbon dioxide (CO2) from the burning of fossil fuels, as well as methane, hydrocarbons, nitrous oxides and water vapour — in the atmosphere is rising. These gases trap heat and lead to global warming.
Unless greenhouse gas levels are stabilised — according to the 2500 scientists from 80 countries who make up the Intergovernmental Panel on Climate Change (IPCC) — Earth's average temperature will rise 1.5-4.5° C during the next century.
To achieve stabilisation, global greenhouse emissions must be rapidly cut by at least 60%. Anything less will not stem global warming.
The average temperature of the atmosphere in 1998 was the warmest since records began in 1866, according to the World Meteorological Organisation. As of October, new monthly temperature records were set in each of the preceding 18 months. Global temperature is almost 0.7° hotter than at the end of the 19th century.
Fifteen of the hottest years on record have occurred since 1980, seven of them since 1990. Researchers from the University of Massachusetts, who analysed data from tree rings, found recent years the warmest in 600 years.
Ice caps
On the assumption that both the Antarctic and Arctic ice caps are likely to remain constant, the IPCC forecasts a gradual sea level rise — from the heat expansion of oceans and melting glaciers — of between 20 centimetres and almost one metre by end of the next century if greenhouse emissions are not cut.
However, there is a growing opinion amongst climate scientists that colossal climate changes are possible and that they can take place within very short periods.
Scientists freely admit that the consequences and interactions that global warming may trigger are so complex that it is impossible to predict when and what sort of events may be unleashed. But they agree that once it begins, it cannot be stopped.
As Dr Will Harrison, a geophysicist at the University of Alaska, warned: "Once climate kicks it off, you can't stop it. Once the bullet's fired, that's it."
Palaeoclimatology — the study of climate in the distant past — sheds some light on what may be in store if global warming is not arrested in the 30 years' grace period it has been estimated we have.
Twelve thousand years ago, the Earth's climate abruptly warmed by 10° in as little as 20 years, and an ice age was brought to an end in slightly more than a human lifespan, reported University of Colorado climatologist James White last October. Analysing ice cores from Antarctica and Greenland, scientists determined that in the north polar region, temperature increased almost 25° within a 50-year period.
The ice cores revealed that the spectacular change in climate coincided with a sudden rise in greenhouse gases in the atmosphere.
"What humans are doing is no different than what natural systems do ... We are simply doing it faster", White pointed out. Such rapid shifts in the climate on a global scale would make it very difficult for humans to adjust.
Scientists believe sudden switches between cold and warm states may be triggered by the complex interactions between a warming atmosphere and melting ice, which at a certain point trigger a rapid change in the circulation of currents in the oceans that distribute heat around the globe.
Dr Gerard Bond, an expert on glaciation at Columbia University, told the March 5 New York Times that the infusion of fresh water from melting glaciers, Arctic ice and tundra could disrupt the strength and flow of dense, salty ocean currents in the North Atlantic.
These currents, said Bond, transport heat into the North Atlantic region. If they weaken, it could set off atmospheric changes that may lead to much colder winters in Europe. Such a chain of events may "at a stretch" even spark a new ice age, said Bond.
Richard Ally of Pennsylvania State University, who specialises in glaciation and the behaviour of ice sheets, told the New York Times that "putting more fresh water into the Atlantic" could "cause things to change in a hurry". He likened the climate to a light switch: a little pressure may not cause change, but when it reaches a certain point, it flips suddenly.
The melting and freezing of Arctic and Antarctic water drive vast ocean currents that affect climate in ways that scientists can only guess at. Because of warm currents, Britain's ports are free of winter ice at the same latitudes as Canada and Russia, where ports are frozen solid.
Sea ice reflects heat back into space that would otherwise make the atmosphere even hotter. As well, much of the Greenland Sea freezes in winter, trapping huge quantities of dissolved CO2. A retarding of this process could add to the accumulation of CO2 and reinforce global warming. Such "feedback" mechanisms may massively accelerate warming.
There is considerable evidence that the steady rise in atmospheric temperature is melting the world's huge reserves of ice. Scientists have long predicted that the coldest parts of the world — Antarctica and the Arctic — would warm much faster than the rest.
Ice shelves
Antarctica has warmed by an average 2.5° — about three times the global average — since the 1940s, and winter temperatures have jumped almost 5°. According to research conducted by the US Geological Survey, Antarctica is now hotter than at any time in the past 4000 years.
Around the Antarctic Peninsula, reported Climate Solutions' Patrick Mazza and Rhys Roth in April, extensive sea ice formed in four out of five winters in mid-century. Since the 1970s, that has dropped to only one or two in every five. Several ice shelves, attached to the continent around the peninsula, are in retreat. The Larsen A ice shelf, after years of slowly melting, suddenly disintegrated in 1995.
In March 1998, a 200 square kilometre piece of ice broke free of the Larsen B ice shelf. British Antarctic Survey (BAS) scientists warn that Larsen B may have entered an "irreversible retreat phase". The Wilkins Ice Shelf, on the other side of the peninsula, shrank by almost 1100 square kilometres last year.
"We have evidence that the shelves in this area have been in retreat for 50 years, but those losses amounted to only about 7000 square kilometres", BAS researcher David Vaughan told the Environmental News Service. "To have retreats totalling 3000 square kilometres in a single year is clearly an escalation. Within a few years, much of the Wilkins Ice Shelf is likely to be gone."
The Larsen and Wilkins shelves are relatively insignificant in Antarctic terms. A much greater concern is if the Ross and the Filchner-Ronne ice shelves begin to collapse.
While the collapse of the Antarctic ice shelves will not cause a discernible rise in sea levels because they already displace water, the shelves prevent massive quantities of ice on the land-based Western Antarctic Ice Sheet from rapidly entering the ocean.
In January, Peter Barrett, from New Zealand's Victoria University in Wellington, told politicians at McMurdo Station, Antarctica, that he believed the Western Antarctic Ice Sheet is on the point of beginning irreversible melting. If that happened, it would result in a six-metre rise in sea levels in less than a century. More than half the world's people live in areas that would be inundated.
The Western Antarctic Ice Sheet is the smaller of Antarctica's two vast sheets, but it is the most active (the vastly larger eastern sheet is cradled in a bowl of mountains). It contains a mind-boggling 3.2 million cubic kilometres of ice, about 10% of the world's ice.
Within the western sheet are five ice streams — enormous glacier-like rivers of ice more than 50 kilometres wide and one kilometre thick — which move towards the ocean at speeds of up to one metre a day, 60 times faster than rest of the sheet. The Ross Ice Shelf — floating ice nearly the size of New South Wales — and similarly sized Filchner-Ronne Ice Shelf block their access to the sea.
Barrett told the New Zealand Press that polar scientists could not be certain when the ice sheet may begin to melt. "It will be too late to do anything about it when we know for certain", he warned.
Ominously, in October 1998, a huge iceberg, measuring more than 150 kilometres long by 35 kilometres wide, broke from the Filchner-Ronne Ice Shelf. This berg was four times larger than the one that broke free of Larsen B in March.
According to David Schneider, writing in the March 1997 Scientific American, the West Antarctic Ice Sheet may have melted at least once before, between 110,000 and 130,000 years ago. "... many geologists believe the sea level [then] stood about five metres higher than it does now — just the additional dollop that would be provided by the melting of the West Antarctic Ice Sheet", explained Schneider.
An article in the August 1995 Scientific American pointed out that the five-metre rise was almost immediately followed by 10-metre decrease — all in the space of 100 or so years!
Arctic
Arctic sea ice is up to a third thinner than it was 20 years ago, according to Dr Peter Wadhams, a reader in polar studies at the Scott Polar Institute in Cambridge.
The Arctic is warming at least twice as fast as the rest of the world. The Nansen Environmental and Remote Sensing Centre in Norway has found that between 1978 and 1994, there was a 4.6% reduction in the extent of Arctic ice and a 5.8% decline in its area — an area the size of France.
Airborne surveys using laser altimeters have revealed that the southern half of the Greenland ice sheet, the largest expanse of land-bound ice after Antarctica, has shrunk substantially in the past five years, it was reported in Science in March. Each year from 1993 to 1998, Greenland lost an average of eight cubic kilometres of ice.
Glaciers
Glaciers form the fourth largest collection of ice in the world, after Antarctica, the Greenland ice sheet and the ice that surrounds the Queen Elizabeth Islands in the high Arctic.
In Alaska, the famous Columbia Glacier's 80-metre high front wall, which once disgorged icebergs into Prince William Sound, has retreated 13 kilometres in the past 16 years. Alaska's more than 1000 other glaciers are also in retreat.
In May 1998, a study by the geological sciences department at the University of Colorado found a "significant decrease in the area and volume of glaciers, especially at mid- and low-altitudes".
The largest glacier on Africa's Mount Kenya has lost 92% of its mass in this century. There remain just 13 glaciers in Spain — there were 27 in 1980. Half the glacier ice in the European Alps and Russia's Caucasus has disappeared during the past century. In New Zealand, glaciers have shrunk 27% since 1890. In the Tien Shan mountain range, between Russia and China, 22% of the volume of its thousands of glaciers has melted over the past 40 years.
High in the South American Andes, the great Quelccaya ice cap, is shrinking by 30 metres a year.
Greenland's glaciers are suspected of flowing faster into the ocean, reported Science in March, due to increased melting that lubricates the bed of the glacier. As the ice picks up speed, friction increases and results in further melting and even greater lubrication. More fresh water is being deposited into the ocean as icebergs as well as through melting.
Tundra
North-western Canada, Siberia and Alaska are thawing too. Scientists at the University of Alaska estimate that average temperatures in these regions have risen 3° in the last 30 years.
According to the August 18 New York Times, Alaska's once permanently frozen ground and pockets of underground ice are melting. "Over thousands of miles, big patches of forest are drowning and turning grey as the ground sinks under them and swamp water floods them. Here and there, deep holes have opened in the earth."
In some places, the point at which the tundra begins has shifted 130 kilometres north over the last century. Scientists have found that over huge areas of Alaska, the ground is just tenths of a degree away from melting.
Melting tundra could have another devastating effect. Carbon in tundra soils is equal to 33% of that in the atmosphere.
Not too late
It is not too late to turn around global warming, but time is short. It is estimated that critical levels of atmospheric C02 will be reached within 30 years at the current levels of greenhouse gas emissions.
The rich capitalist countries refuse to seriously reduce greenhouse gases reaching the atmosphere. North America, Europe, Japan, Australia and New Zealand are responsible for more than 80% of past emissions and 75% currently. Yet these governments place the protection of the profits and "competitiveness" of their powerful corporations above the welfare of the world's people.
The US is the worst offender. With around 4.5% of the world's population, in 1990 the US emitted 36.1% of all greenhouse gases. Greenhouse gas emissions in the US are predicted to increase 30% from 1990 levels by 2010.
We urgently need a massive reduction in greenhouse gas emissions. To achieve that requires fundamental changes in the way the world is organised. The private profit system, which has brought us to the brink of calamity, needs to be replaced by a system that puts people and the planet they live on before profits.