Burning crops darken Arctic sky, speed polar melt

The collapse of the Soviet Union and the loosening of state control over crop burning in Russia has had an unexpected impact in the Canadian North: the unleashing of massive amounts of soot that is settling on Arctic sea ice and speeding the ongoing polar meltdown.

How the end of the Cold War has fuelled Arctic warming is detailed in a new report by U.S. scientists that points a finger at Saskatchewan farmers for sending some "black carbon" into the Arctic environment but largely blames Russia for the rising number of smoke plumes drifting north and creating a "critical" challenge for Canada and other polar nations.

The findings were released ahead of an international meeting next week at the University of New Hampshire aimed at curbing the impact of agricultural burning — a problem scientists say has emerged as a major factor in Arctic warming and thinning sea ice.

"These fires weren't part of our standard predictions, they weren't in our models," said Daniel Jacob, a Harvard University climate researcher who participated in a multi-agency U.S. government experiment last spring off the northern coast of Alaska.

Teams of scientists led by NASA, the National Oceanic and Atmospheric Administration and the U.S. Department of Energy gathered data on long-range polar pollutants and used NASA's DC-8 "flying laboratory" to sample smoke plumes drifting over Alaska and parts of Arctic Canada.

"What they found surprised them," says the report, Agricultural Fires and Arctic Climate Change, released Wednesday by the Boston-based Clean Air Task Force.

"Over the course of the month, the airplanes encountered up to 50 smoke plumes originating from fires in Eurasia, more than 4,800 kilometres away. Analysis of the plumes, combined with satellite images, revealed the smoke came from agricultural fires in Northern Kazakhstan-Southern Russia and from forest fires in Southern Siberia."

Forest fires have long been identified as a major source of Arctic pollutants, but the study concludes that agricultural fires — typically used to clear stubble from harvested crops and prepare land for the next growing season — are sending more and more smoke northward, warming the Arctic troposphere and then depositing soot on polar snow and sea ice.

The darkened surface reduces the reflective features of the snow and ice and absorbs more heat from the sun, compounding the overall effects of rising temperatures caused by global climate change, the report states.

The study attributes much of the rise in farm-related Arctic pollution to changing land-use practices in post-Soviet Russia and Kazakhstan.

"The collapse of the USSR in 1991 brought an end to the socialist command economy that had dominated agricultural production for decades," the report states. "In the absence of state subsidies, the large farming co-operatives that had supported Soviet industrial society were abandoned, leading to the re-growth of vegetation across much of the countryside. As smaller private enterprises emerged, they faced a changed landscape; cultivated fields now existed alongside wild grasslands and dry brush, creating ideal conditions for fire."

The report says the largely unregulated use of agricultural fires in Russia is now responsible for about 80% of the crop-related black carbon reaching the Arctic.

Canada is contributing just over 1% of the total, the report notes, with most of those agricultural emissions coming from Saskatchewan.

Although farmland burning appears to have declined in recent years in the province, satellite records "nevertheless show extensive fire activity in the crop and grasslands of southern Saskatchewan between January and June 2008," the report says.

The U.S. researchers say the findings about the impact of agricultural fires should prompt stronger action from the Arctic Council, an eight-country organization that includes Russia and Canada and which recently pledged to curb black carbon emissions reaching polar latitudes.

"Targeting these emissions offers a supplemental and parallel strategy to carbon dioxide reductions, with the advantage of a much faster temperature response, and the benefit of health risk reductions," says Ellen Baum, senior scientist of the Clean Air Task Force. "In addition, we have the know-how to control these pollutants today."

Another U.S. study announced on Wednesday also had bad news for the Arctic.

A University of Florida-led research paper to be published in the journal Nature predicted that thawing Arctic permafrost will pump one billion tonnes of carbon dioxide annually into the atmosphere by the end of this century.

Although greater plant growth in the warming Arctic will absorb more CO2 and initially balance the effects of melting permafrost, the research shows the increased vegetation won't fully compensate for carbon unlocked from the soil.

"At first, with the plants offsetting the carbon dioxide, it will appear that everything is fine, but actually this conceals the initial destabilization of permafrost carbon," said study co-author Ted Schurr in a statement released by the university. "But it doesn't last, because there is so much carbon in the permafrost that eventually the plants can't keep up."

A third study — on projected sea-level rises caused by melting Arctic ice — identified coastal cities in the northeast corner of North America, including Halifax, New York and Boston, as the places most likely to face adverse effects.

The study led by the National Center for Atmospheric Research at the University of Colorado incorporated forecasted effects from melting of the Greenland Ice Sheet with earlier predictions about overall increases in ocean levels caused by global warming.

The study, to be published this week in the journal Geophysical Research Letters, found that continued moderate melting of Greenland's ice cap would shift Atlantic Ocean circulation by the end this century and cause sea levels in northeastern Canada and the U.S. to increase between 30 and 51 cm more than in other coastal zones.

"If the Greenland melt continues to accelerate, we could see significant impacts this century on the northeast U.S. coast from the resulting sea level rise," said NCAR scientist Aixue Hu. "Major northeastern cities are directly in the path of the greatest rise."

The researchers also note that "more remote areas in extreme northeastern Canada and Greenland could see even higher sea-level rise" than heavily populated areas to the south.

Those areas include much of Ellesmere Island, Baffin Island, Quebec's Ungava Peninsula and Labrador.