This image of Greenland summer 2012 air temperature anomalies at the 925 hPa level (about 3,000 feet above the surface) shows that all of Greenland experienced warmer than average temperatures, with the strongest warming along the west coast. Temperatures are compared to the 1981 to 2010 average. Graphic: National Snow and Ice Data Center / NOAA/ESRL Physical Sciences Division

By Gerard Wynn
15 February 2013 LONDON (Reuters) – Vast uncertainty remains over the causes of melting Arctic sea ice and when it may disappear altogether during the summer, which would have consequences for oil explorers, shipping firms and the fight against climate change. The answer will depend on the balance of natural and manmade causes. Those causes include warmer air and seas as a result of greenhouse gas emissions, variations in atmospheric circulation, and a faster southward ice drift down the east coast of Greenland. A major study said last month that science had underestimated the impact of soot, also called black carbon, adding another complication to an already difficult task of making a forecast. The Arctic region accounts for 15 percent of the world’s undiscovered oil and 30 percent of its undiscovered gas, the U.S. Geological Survey estimates. Scientists are still unsure about the exact causes of sea ice melt, and predictions of when the North Pole could have an ice-free summer vary from 2015 to 2080 or later, with forecasts centring around 2040. Oil producers including Russia’s Rosneft, Norway’s Statoil, U.S.-based Exxon Mobil and Anglo-Dutch Shell are preparing to drill in areas of melting sea ice, despite the technological difficulties and costs. Last September sea ice reached its lowest level in the satellite record, which dates back to 1979, a development that has implications for local native communities and wildlife, local coastal erosion, and possibly northern hemisphere weather. Observations of the extent of Arctic sea ice made by ships in earlier decades suggest last year’s record would at least stretch back to a cold period in the mid-nineteenth century known as the Little Ice Age. Data show a clear trajectory of ice losses in recent decades. An acceleration last year past a previous record in 2007 reflects a self-perpetuating process as well as thinning over many decades. Under the albedo effect, dry snow reflects more than 80 percent of solar radiation; bare ice 65 percent; and open water just 5 percent. And increasing expanse of open water each summer warms up faster than ice-covered sea, meaning new ice will be thinner and more vulnerable the following year. [more]

COLUMN-Ice-free Arctic Ocean in 2030?: Wynn