Norm Dixon
Hollywood's global warming apocalypse flick, The Day After Tomorrow, has focused attention on how the melting of polar ice, the Arctic tundra and the world's glaciers can trigger abrupt climate change. There is now overwhelming evidence that the world's huge reserves of ice are melting at an alarming rate due to industry-induced global warming.
Despite The Day After Tomorrow's fantastically exaggerated scenario of an ice age enveloping the northern hemisphere within weeks, the scientific theory which it is very loosely based on is sound.
On March 5, NASA's Science@NASA website warned that "global warming could plunge North America and Western Europe into a deep freeze, possibly within only a few decades". The US government agency agreed with the analysis of researchers from the Oregon State University (OSU), published in the science journal Nature in February 2002, that explained how the influx of massive quantities of freshwater into the polar oceans could slow down or even halt the global thermohaline circulation (also known as the Great Ocean Conveyor), the gigantic ocean currents that bring warm water from the tropics to otherwise frigid parts of the world.
"Without the vast heat that these ocean currents deliver — comparable to the power generation of a million nuclear power plants — Europe's average temperature would likely drop 5-10 [degrees celcius], and parts of North America would be chilled somewhat less. Such a dip in temperature would be similar to global temperatures toward the end of the last ice age", Science@NASA reported. Robert Gagosian, president and director of the Woods Hole Oceanographic Institution, told Science@NASA that this shift in ocean currents could come "surprisingly soon", perhaps within 20 years.
The 2500 scientists from around 100 countries who make up the Intergovernmental Panel on Climate Change (IPCC) have warned that unless levels of greenhouse gases in the atmosphere — primarily carbon dioxide (CO2) from the burning of fossil fuels — are stabilised, the Earth's average temperature will rise 1.4-5.8C by 2100. To achieve stabilisation, total global greenhouse gas emissions must be cut to at least 60% compared to emissions within 25 years.
The IPCC also forecasts, on the assumption that the Antarctic and Arctic ice caps remain constant, a gradual sea level rise of between 20 centimetres and almost one metre by 2100 if greenhouse gas emissions are not significantly reduced.
'World's canary'
"We are the canary in the mineshaft", Gunter Weller, executive director of the University of Alaska's Centre for Global Change and Arctic System Research, told the October 7 Christian Science Monitor. He was referring to the fact that scientists' predictions that the coldest parts of the world — Antarctica and the Arctic — will warm much faster are coming true.
The Arctic region is warming more than twice as fast as the rest of the world, according to Robert Corell, chairperson of the Arctic Climate Impact Assessment, whose 1800-page report was handed to Europe's environment ministers last November.
According to the Science@NASA web site on March 5, NASA and other US government weather satellites, which use cloud-penetrating microwaves, "clearly show a long-term decline in the 'perennial' Arctic sea ice (the part that remains frozen during the warm summer months). According to a 2002 paper by Josefino Comiso, a climate scientist at NASA's Goddard Space Flight Centre, this year-round ice has been retreating since the beginning of the satellite record in 1978 at an average rate of 9% per decade ... More recent data peg the rate at 14% per decade, suggesting that the decline in Arctic sea ice is accelerating." The Arctic ice pack is also 40% thinner than it was in the 1960s.
The Greenland ice sheet accounts for 10% of the world's ice. Waleed Abdalati, from the Earth Sciences Department of NASA's Goddard Space Flight Centre, told the October 13, 2002, Washington Post that in some parts of the south Greenland coast, the ice cover is thinning at the rate of one metre each year. There is a "net loss of ice, particularly in the south". This is corroborated by the observations of Greenland's indigenous Inughuit people, who report an increase in the number of icebergs in recent years.
Alaska, northern Canada and Siberia are similarly feeling the heat. In Alaska, average winter temperatures have risen about 4.5oC over the past 30 years. According to the University of Colorado's Institute of Arctic and Alpine Research's Mark Meier in 2002, glaciers in Alaska and northern Canada are shedding ice at twice the rate as was the case in 1988.
"Large 91×ÔÅÄÂÛ̳ of northern forests are collapsing into swamps of melting permafrost [tundra]; 91×ÔÅÄÂÛ̳ of shoreline on the Arctic coast have thawed, making them vulnerable to storms; and the Arctic's largest ice shelf, solid for 3000 years, broke up [in September 2003] due to warmer temperatures", the October 7 Christian Science Monitor reported.
The indigenous peoples of the Arctic region have long relied on hunting seals, salmon, whales and other wildlife. Richard Kocan of the University of Washington's School of Aquatic and Fisheries Science points out that Alaskan and northern Canadian rivers have become 2.8oC warmer in 20 years, making them almost lethal for salmon in summer.
Antarctica
Antarctica has also warmed by an average 2.5oC since the 1940s, and winter temperatures there have jumped almost 5oC. The Antarctic ice shelves are in retreat. The Larsen A ice shelf, after years of slowly melting, suddenly disintegrated in 1995. The Wilkins Ice Shelf shrank by almost 1100 square kilometres in 1998. In March 1998, a 200 square kilometre piece of ice broke free of the Larsen B ice shelf.
In 2002, the 3400-square kilometre Larsen B shelf — at least 12,000 years old and up to 70 storeys thick — disintegrated into thousands of icebergs in the space of a few months (dramatic satellite images of the collapse are available at ) Glaciers around the area of ice shelf accelerated immediately after it collapsed.
The Larsen and Wilkins shelves are relatively insignificant in Antarctic terms. A much greater concern is if the massive Ross and the Filchner-Ronne ice shelves begin to collapse. The Ross and the Filchner-Ronne ice shelves prevent the gigantic land-based Western Antarctic Ice Sheet from rapidly entering the ocean, where it would melt rapidly.
The Western Antarctic Ice Sheet is the smaller of Antarctica's two vast sheets, but it is the most active (the vastly larger Eastern Antarctic Ice Sheet is cradled in a bowl of mountains). It alone contains a mind-boggling 3.2 million cubic kilometres of ice, about 10% of the world's ice — enough to raise the sea level six metres. (If the eastern sheet melted, the sea level would rise more than 60 metres!)
Within the western sheet are five ice streams — enormous 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. The Ross Ice Shelf — floating ice nearly the size of New South Wales — and similarly sized Filchner-Ronne Ice Shelf prevent these ice rivers from sliding into the sea where they would rapidly melt.
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 followed by 10-metre decrease — all in the space of 100 or so years!
The May 2002 edition of Science reported that researchers from the Oregon State University, the University of Toronto and the University of Durham in Britain had found that the "global meltwater pulse 1A", the massive and unusually abrupt 23-metre rise in the sea level about 14,200 years ago, was caused by the partial collapse of both major ice sheets in Antarctica. The sea level took just 500 years to reach that height; in each year of that period, the sea-level rise was more than the total rise during the previous 100 years.
This melting was triggered by a runaway greenhouse effect, caused by concentrations of CO2 in the atmosphere, causing the Earth's climate to rapidly warm. About 12,700 years ago, the fresh water from melted polar ice, Arctic tundra and glaciers seems to have reached the concentration required to severely disrupted the North Atlantic thermohaline circulation. It triggered a 15oC drop in the northern hemisphere's average temperature in the space of a three decades — an event known as the Younger Dryas. This cold spell lasted 1300 years. About 8200 years ago, a similar warming triggered a century-long temperature drop of around 2.8-3.3oC.
On January 27, 1999, Peter Barrett, from New Zealand's Victoria University in Wellington, told politicians gathered at McMurdo Station, Antarctica, that he believed the Western Antarctic Ice Sheet is on the point of beginning to irreversibly melt.
Ominously, the calving of monstrous Antarctic icebergs is becoming a regular occurrence. In October 1998, a berg measuring more than 150 kilometres long by 35 kilometres wide broke from the Filchner-Ronne Ice Shelf. In March 1999, two massive icebergs broke away from the Ross Ice Shelf. Researchers at the University of Wisconsin Madison's Antarctic Meteorological Research Center discovered the icebergs, one of which, at about 270 kilometres long and 40 kilometres wide, was as large as Jamaica. The second iceberg was 130 kilometres long and 20 kilometres wide. In May 2002, a 76-kilometre-long, 7.4 kilometre-wide iceberg broke off from the Ross Ice Shelf.
From 91×ÔÅÄÂÛ̳ Weekly, June 9, 2004.
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