The yellow line reveals the gap between this year's minimum and average summertime minimum from 1981 to 2010. Photo by NASA/Goddard
GREENBELT, Md., Sept. 16 (UPI) -- On September 11, satellites found the arctic sea ice cover at its smallest, its summertime minimum. Its shrunken coverage measured just 1.7 million square miles in size.
According to NASA and scientists with the agency's National Snow and Ice Data Center, it was the fourth-smallest summer minimum on record.
But unlike previous lows, researchers say this summer's minimum was not exacerbated by meteorological conditions. In 2012, for example, the record for smallest arctic sea ice cover was achieved with the help of an August cyclone, which fractured sea ice and accelerated the cover's recession.
This year, air and ocean temps were simply exceptionally high. Global averages were the highest they've ever been this summer, and current trends suggest 2015 will be the hottest year on record. And as each summer gets hotter and hotter, the arctics sea ice coverage grows thinner, weaker and easier to melt the next year.
"The ice cover becomes less and less resilient, and it doesn't take as much to melt it as it used to," Walt Meier, a sea ice scientist at NASA's Goddard Space Flight Center, said in a news release. "The sea ice cap, which used to be a solid sheet of ice, now is fragmented into smaller floes that are more exposed to warm ocean waters."
Each summer, Meier says warming ocean waters are finding their way into new imperfections in the sea ice, melting the cover from within.
Just as the climate's hottest years have been bunched within the last two decades, so too have the smallest summer minimums. The ten smallest have all been recorded within the last 11 years. This year's low was nearly 700,000 square miles smaller than the average low from 1981 to 2010.
Scientists say it's not clear whether the El Niño pattern in the Pacific Ocean has played a role shrinking arctic ice coverage, but as the cap's thicker strongholds of ice weaken, the summer minimum is likely to become ever more vulnerable to faraway weather systems.
"Historically, the Arctic had a thicker, more rigid sea ice that covered more of the Arctic basin, so it was difficult to tell whether El Niño had any effect on it," explained Richard Cullather, a climate scientist at Goddard. "Although we haven't been able to detect a strong El Nino impact on Arctic sea ice yet, now that the ice is thinner and more mobile, we should begin to see a larger response to atmospheric events from lower latitudes."