Tuesday September 25, 2012
Reshaping the Arctic
By JOHN VIDAL and MONTE MORIN
Polar sea ice shrinks to record lows, triggering uncertainties in weather patterns.
WE are a few hundred miles from the North Pole. The air temperature is -3°C, the sea, freezing. All around us in these foggy Arctic waters at the top of the world are floes – large and small chunks of sea ice that melt and freeze again with the seasons.
Arne Sorensen, our Danish ice pilot, is 18m up in the crow’s nest of the Arctic Sunrise vessel. Visibility is just 200m and he inches the 1,000-tonne Greenpeace ice-breaker forward at two knots through narrow passages of clear water. The floes are piled up and compressed in fantastic shapes. Two polar bears on our port side lift their heads but resume hunting. Sorensen has sailed deep into ice at both poles for 30 years, but this voyage is different, he says. The edge of the Arctic ice cap is usually far south of where we are now at the very end of the melt season. More than 600,000sqkm more ice has melted in 2012 than ever recorded by satellites. Now, the minimum extent has nearly been reached and the sea is starting to refreeze.
“This is the new minimum extent of the ice cap,” he says – the frontline of climate change. “It is sad. I am not doubting this is related to emitting fossil fuels to a large extent. It’s sad to observe that we are capable of changing the planet to such a degree.”
The vast polar ice cap, which regulates the Earth’s temperature, has this year retreated further and faster than anyone expected. The previous record, set in 2007, was officially broken on Aug 27 when satellite images averaged over five days showed the ice then extended 4.11 million sqkm, a reduction of nearly 50% compared with just 40 years ago. And since then, the ice just kept melting. Satellite pictures on Sept 16 showed the cap covering only 3.42 million sqkm. That’s the smallest Arctic ice cover since record-keeping began in 1979, the US National Snow and Ice Data Centre (NSIDC) said. This year, 11.7 million sqkm of ice melted, 22% more than the long-term average of 9.18 million sqkm. The record minimum extent has not just been broken, it has been smashed to smithereens, adding weight to predictions that the Arctic may be ice-free in summer within 20 years, say British, Italian and American-based scientists on the Arctic Sunrise. They are shocked at the speed and extent of the ice loss.
Cambridge University sea-ice researcher Nick Toberg, who has analysed underwater ice thickness data collected by British nuclear submarine HMS Tireless in 2004 and 2007, said: “This is staggering. It’s disturbing, scary that we have physically changed the face of the planet. We have about four million sqkm of sea ice. If that goes in the summer months that’s about the same as adding 20 years of carbon dioxide at current (human-caused) rates into the atmosphere. That’s how vital the Arctic sea ice is.”
NSIDC scientist Julienne Stroeve adds: “In the 1970s, we had eight million sqkm of sea ice. That has been halved. We need it in the summer. It has never decreased like this before. We knew the ice was getting thinner but I did not expect we’d lose this much this year. We broke the record by a lot.
“The acceleration of the loss of the extent of the ice is mostly because the ice has been so thin. This would explain why it has melted so much this year. By June, the ice edge had pulled back to where it normally is in September.”
In the past, Stroeve has shown that ice melt has been happening far faster than the models predicted. Her new research, published last month in the journal Geophysical Research Papers, shows humans may have been responsible for most of the ice loss in recent decades.
“It suggests 60% of the observed decline in ice extent in Septembers from 1953-2011 was due to human activity. The decline is linked to the increase in temperatures,” she says. “This year is significant. At the moment, the (ice extent) is below what the next Intergovernmental Panel on Climate Change (IPCC) report will show in 2014. We are on the extreme edge of the models, suggesting that ice loss is happening much faster than the models suggested.”
All over the Arctic, the effects of accelerating ice loss and a warming atmosphere are being seen. The ecology is changing rapidly as trees and plants move north, new beetles devastate whole forests in Canada, Siberia and Alaska, and snowfall increases.
Whole coastal communities may have to be moved to avoid sea erosion. With the ice loss has come a rush by industry for Arctic resources. Oil, gas, mining and shipping companies are all expanding operations into areas that until only 20 years ago would have been physically impossible. Recently, a historic first drilling operation by Shell in the Chukchi Sea off Alaska was halted after sea ice was seen moving towards the oil company’s drill ship.
Other new research suggests that the loss of ice could be affecting the path and speed of the jet streams, possibly explaining why extreme weather in the northern hemisphere is lasting longer. From now until June, the Arctic sea ice will refreeze, growing up to 100,000sqkm a day until the melt season begins again next year.
But, says Toberg, because of the massive melt this year, there will be less old, or multi-year, ice, which is thicker and less prone to melting. The new ice will be more vulnerable to melt, hastening the loss of ice next year. Now, “feedbacks” are thought to be hastening the ice retreat.
In recent summers, say ice experts, Arctic sea surface temperatures have been well above normal, partly because there is less ice to reflect heat back into the atmosphere. The darker open waters now absorb more solar radiation, accelerating the melt.
The longer term implications of the great melt of 2012 are hard to call, say climate scientists who caution that more research is needed. Sea ice plays a critical role in regulating climate, acting as a giant mirror that reflects much of the sun’s energy, helping to cool the Earth.
What is suspected is that the formation of the sea ice produces dense salt water which sinks, helping to drive the deep ocean currents. Without the summer sea ice, many scientists fear this balance could be upset, potentially causing big climatic changes.
“The Arctic ice cover is a lid on the planet that regulates the temperature. By taking it off you are warming it. Temperatures depend on it,” says Toberg. “We can expect the Arctic to be ice-free in summer within 20 years,” she says. “That does not mean that natural ice variability cannot bring it back again, but the trend, we think, will be downward.”
Scientists believe that the quick thaw of Arctic sea ice will cause extreme weather this winter in North America and Europe. Jennifer Francis, a researcher at the Institute of Marine and Coastal Sciences at Rutgers University, argued that shrinking Arctic ice can be tied to such recent weather events as prolonged cold spells in Europe, heavy snows in the north-eastern US and Alaska, and heat waves in Russia.
The loss of Arctic ice has several effects. Ice reflects heat and solar energy back into space. With less ice cover, that heat energy is instead absorbed by the ocean, which warms and melts more ice.
Currently, the Arctic region is the fastest-warming region on the planet, and the change in temperature will probably influence weather patterns here and in Europe, according to Francis.
The heating and cooling of Arctic seawater has been affecting the jet stream – the river of air that flows from west to east high above the Earth’s surface – and has slowed it down, Francis said. The jet stream controls the formation and movement of storm systems, so when its movement slows, weather conditions persist for longer periods of time over the same area. They get “stuck.”
“If you’re in a nice dry pattern with sunny skies, it’s great if it lasts for a few days. But if it lasts for a few weeks, well then you’re starting to talk about a drought,” Francis said. “If you have a rainy pattern and it hangs around for a long time, then that becomes a situation that could lead to flooding.”
Arctic warming will influence weather to the south during the late fall and winter. While Francis said it would probably result in severe weather this winter, it was impossible to predict when and where those events would occur.
Record ice melts this year and in 2007 have alarmed many scientists, mostly because they thought it would take many more years to reach this state.
James Overland, an oceanographer with the National Oceanic and Atmospheric Administration, said forecasts failed to account for the physics of lost solar energy reflection and warming ocean water.
“These are really surprises to most scientists,” Overland said. “In looking at climate models that are used to look forward, they’ve tended to say the Arctic may be ice-free by 2040 or 2050. It looks like things are happening a lot faster, and it’s because not all of the physics that we’re seeing today were well-handled in these climate models.”
Overland, who is also an associate professor at the University of Washington’s Department of Atmospheric Sciences, said these effects are known as “Arctic amplification” and would carry heavy consequences for wildlife like polar bears and walruses by reducing their habitat. – Agencies