Friday, March 25, 2011

Arctic Sea Ice extent winter maximum continues sea ice decline



Arctic sea ice extent has just passed it's maximum - estimated to be March 7 this year. Only this year it has tied with 2006-2007 as the lowest on record according to satellite records that began in 1979.

The seven lowest maximum Arctic sea ice extents measured by satellites all have occurred in the last seven years, according to Colorado University-Boulder Research Scientist Walt Meier from the National Snow and Ice Data Center. "I'm not surprised by the new data because we've seen a downward trend in winter sea ice extent for some time now." he said.


According to the The National Snow and Ice Data Center, the sea-ice maximum on March 7 was 471,000 square miles (1.2 million square kilometers) below the 1979 to 2000 average -- an 8 percent decline.

"I think one of the reasons the Arctic sea ice maximum extent is declining is that the autumn ice growth is delayed by warmer temperatures and the ice extent is not able to 'catch up' through the winter," said Meier. "In addition, the clock runs out on the annual ice growth season as temperatures start to rise along with the sun during the spring months." said Walt Meier.

Arctic sea ice plays a key role in the global climate system by coolling air and water masses, contributing to global ocean circulation and reflectng solar radiation back into space. As more and more sea ice is lost, more dark ocean allows more radiation to be absorbed increasing temperatures in an Albedo feedback loop. A study has already shown that current Climate Models under estimate loss of reflectivity in the Arctic.

Sea Ice extent is just one measurement used by scientists in assessing Arctic ice. The thickness and condition of sea ice are also important considerations. The last few years have seen a dramatic drop in multi-year ice - ice that repeatedly survives the summer melt season and which provides the greatest difficulty for ships to navigate through.

In December 2009 Dr David Barber reported that sea ice thickness is in rapid decline, with much of the purported multi-year ice as detected by microwaves from satellite proven by new research to be 'rotten' ice unexpectedly thin that electromagnetically fools the satellite measurement instruments.

"Our results are consistent with ice age estimates that show the amount of multiyear sea ice in the northern hemisphere was the lowest on record in 2009 suggesting that multiyear sea ice continues to diminish rapidly in the Canada Basin even though 2009 aerial extent increased over that of 2007 and 2009," Dr David Barber concludes in his paper which was published in Geophysical Research Letters.

In a recent report by Reuters the US Navy's chief oceanographer, Rear Admiral David Titley, commented about the difficulty in finding a thick enough multi-year ice sheet to put an ice camp for military training purposes this year.

Winter temperatures across much of the Arctic were warm, reaching 4 to 11 degrees Fahrenheit (2 to 6 degrees Celsius) above normal in January with a strong negative arctic oscillation which brought snowstorms and freezing weather to the mid-latitudes of North America, the UK and Europe. While cold air has chilled the mid-latitudes, the Arctic has been warming at an unprecedented rate.

"The meltdown of winter sea ice is yet another sign that climate change is underway, and yet some members of Congress continue to deny it, preferring to preserve polluters' profits over saving the future of our planet as we know it," said Shaye Wolf, climate science director at the Center for Biological Diversity's Climate Law Institute.

A vocal, but well funded, minority of people continue to stymie action on climate change particularly in the US, but also to a much lesser extent Australia. Several attacks are being made in the US Congress on the Obama administration use of the Clean Air Act to regulate carbon dioxide pollution.

"We possess the technology to curb greenhouse pollution and slow global warming now," said Wolf. "New and updated Clean Air Act standards for carbon dioxide, methane and nitrous oxide will spur additional technological innovation, create jobs, save lives and slow the melting of the Arctic sea ice -- but not unless Congress lets the EPA do its job."

Want to watch a quick overview of the changes in the Arctic?, then Climate Denial Crock of the week with Peter Sinclair provides a good introduction from September 2010 :



Sources:
* Adapted from University of Colorado at Boulder news, March 23, 2011 - Measurements of winter Arctic sea ice show continuing ice loss, says CU-Boulder study
* Adapted from Centre for Biological Diversity Media release, March 24, 2011 - Winter Sea Ice Hits Historic Low