Friday, September 28, 2012

Vanishing Arctic sea ice is rapidly changing global climate

By Paul Beckwith

Adapted from a September 21, 2012, post at the Sierra Club Canada blog

About 5 million years ago continental drift pushed North and South America together, creating the Isthmus of Panama where the Central American Seaway ocean passage had previously existed. The Pacific and Atlantic were no longer connected, drastically altering global ocean currents and atmospheric circulation patterns. As the Atlantic Gulf Stream strengthened, it carried vast amounts of moisture into the northern regions. The Arctic eventually cooled and it’s estimated sea ice cover has existed continuously in the Arctic Ocean for 3 million years, possibly for as long as 13 million years.

Slow cycling between cold and warm periods occurred on Earth many times due to the planet's changing orbit, tilt, and position relative to the sun. This caused the sea ice to wax and wane in size but it always persisted, never vanishing. Not any longer. The sea ice will disappear for longer and longer periods over the coming years until it is finally gone for good, likely within a decade.

The world will be a different place - just like the world from 3, or even 13, million years ago. No longer will the bright white parasol on the top of the world reflect sunlight and keep the Arctic cool. Dark seawater will absorb light and rapid Arctic warming will quickly decrease temperature gradients between the pole and equator. Jet streams will slow down, meander and change tracks. Storms will change in location, intensity, frequency, and speed and everything that humans know about weather and seasons for growing food will be obsolete. Everything.

Higher global temperatures will cause more evaporation, putting more water vapor into the atmosphere. Condensing into clouds, huge amounts of heat will be released, fueling even larger and more frequent storms.

Throw out the models that project disturbing climate effects in 2100. They're happening now! Already we're seeing rising sea levels from the massive and accelerating Greenland ice melt. The rapid warming of southern oceans is melting and destabilizing Antarctic ice from below, causing enormous chunks to break off (we’ve all seen them on TV). And big increases in Arctic temperatures mean terrestrial permafrost is melting and the now-warmer continental shelf sea floor is releasing increasing amounts of methane gas, a potent climate change gas.

Why is the sea ice getting hammered? Feedback loops. Unknown unknowns

NASA images showing the difference between sea ice cover between 1980 and 2012.
A very rare cyclone churned up the entire Arctic region for over a week in early August, destroying 20% of the ice area by breaking it into tiny chunks, melting it, or spitting it into the Atlantic. Cold fresh surface water from melted sea ice mixed with warm salty water from a 500 metre depth! Totally unexpected. A few more cyclones with similar intensity could have eliminated the entire remaining ice cover. Thankfully that didn't happen. What did happen was Hurricane Leslie tracked northward and passed over Iceland as a large storm. It barely missed the Arctic this time. Had the storm tracked 500 to 600 kilometres westward, Leslie would have churned up the west coast of Greenland and penetrated directly into the Arctic Ocean basin.

We dodged a bullet, at least this year. This luck will surely run out. What can we do about this? How about getting our politicians to listen to climatologists, for starters.

Posted with author's permission. Earlier posted at Sierra Club Canada. Paul Beckwith is a PhD student with the laboratory for paleoclimatology and climatology, department of geography, University of Ottawa. 

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