Top ten weather stories for 2007: story one
1. Vanishing Ice at the Top of the World
On September 12, satellite images over Arctic waters revealed that sea ice in the area had shrunk to about 4 million square km - a minimum not seen for possibly more than a century. The ice shrinkage stunned scientists, who found 23 per cent less sea ice than the previous record of 5.3 million square km in 2005. It was as if an ice chunk the size of Ontario had disappeared in one year. Since 1971, and particularly since 1990, sea ice in the Arctic Ocean has been decreasing significantly on a hemispherical scale. But this year’s “big melt” was a shocker.
The main channel through the Canadian waters of the Northwest Passage was nearly ice-free and completely navigable for about five weeks in August and September. Of its 2,300 km length, there was only about 20 km of ice instead of the usual 400 km. In 2007, ships as small as sailboats could have plied the normally ice-infested waters of the venerable Passage -- and nearly 100 vessels did.
Description of Image
In September 2007, Parry Channel, the northern, deep-water route of the Northwest Passage, became almost clear of ice from one end to the other for the first time in recorded history. This RADARSAT-1 satellite image recorded the remarkable event. Image: © Canadian Space Agency, Imagery processed by MacDonald, Dettwiler and Associates, 2007.
The unprecedented shrinkage of Arctic sea ice is a direct response to several years of favourable Arctic winds pushing old ice into the Atlantic, as well as persistent, year-round warming of the North and a dramatic transformation of its surface from a highly reflective white snow or ice to dark heat-absorbing sea water. The last two winters were the warmest on record in northern Canada, with 2005-2006 the warmest in the past 60 years. Further, 5 of the 10 warmest years in the past 60 have occurred since 2001. The last cold winter occurred nearly 15 years ago.
This year’s Arctic ice shrinkage (similar to what some climatologists envisioned would happen 30 years from now) meant the 2007 fall freeze-up started from a huge deficit, making it harder for the ice to grow back and increasing the likelihood that sea ice will shrink even more next summer. Scientists are now even more convinced that the Arctic climate system is heading toward a more ice-free state during the summer months, and that human-caused global warming is playing a significant role. And while the disappearing ice is having an immediate impact on northern peoples, the effects of this unprecedented loss outside the Arctic is uncertain. What we do know is that ice exerts an enormous control on global climate and its sudden loss could have profound impacts on weather well beyond the Arctic’s borders.
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