By Galen Rende
The first six months of 2016 brought record-setting declines in Arctic sea ice, leaving polar scientists with the task of investigating the causes of this substantial drop-off. This year’s maximum annual ice extent, measured on March 24, was 431,000 square miles below average and 5,000 square miles below the previous record-low, set in 2015.
Globally, the past 14 months have each been the hottest ever recorded. In the Arctic, however, temperatures have been increasing at more than twice the rate of the rest of the Northern Hemisphere in a phenomenon known as Arctic amplification. In January, temperatures in the Arctic were a startling 5 degrees Celsius above average, marking yet another historic milestone on the climate record.
The story of Arctic sea ice has become increasingly unpredictable, as early-year storms and unusual changes in atmospheric circulation resulted in the movement of warm, humid air into the Arctic Circle.
Dr. Alek Petty, an ESSIC Research Associate based at the NASA Goddard Space Flight Center in Greenbelt, Maryland, has been closely following the progression of Arctic sea ice. He notes that in the beginning of 2016, a massive storm originating off the coast of Ireland made its way up into the Arctic, wreaking havoc on the already thin, heat-burdened ice.
“The storm brought in a lot more heat and moisture than it normally does in the winter and probably helped push the ice back, maybe even causing some melt to occur, thinning the ice,” Petty says. “This storm is something we have never seen before.”
But the winter storm was only the beginning of what has been a tumultuous year for Arctic sea ice. A study out of the NOAA Pacific Marine Environmental Laboratory in Seattle, Washington found that temperatures at the North Pole remained high throughout the winter due to an anomaly newly-dubbed as a split polar vortex. In this scenario, instead of maintaining one centralized, cold, low pressure system at or near the North Pole, two of these systems formed opposite each other in the North Pacific and Atlantic Oceans. The gap running through the polar vortex allowed warmer winds to brush through the Arctic from as far south as the tropics, causing temperatures to remain unusually high all the way into May.
Petty asserts that these high temperatures have been matched by equally low measurements of sea ice.
“Virtually every month this year has been a record breaking month,” Petty contends.
“With the exception of March, each month from January to June has set a new record-low.”
The 2016 measurements reflect a larger trend of declining Arctic sea ice through the turn of the century, as the maximum ice cover this year was just 40 percent of what it was four decades ago.
After a short respite of colder temperatures in June, Petty says that the Arctic is heating up once again. The changes in the last two months have polar scientists scrambling to alter their models and predictions.
“This is the scientific process in action, where people are reacting to changes on a daily basis and people alter their forecasts,” says Petty. “These events have never happened before. It’s very hard for scientists to say ‘when X happens, Y happens,’ because we haven’t experienced ‘X‘ before. Our models aren’t ready for these events.”
If anything, this year has reminded researchers that more must be done to understand the underlying causes of extreme climatic changes. Currently, Petty is examining data from NASA’s Operation IceBridge, which flew over the Arctic in July, to better grasp the factors influencing sea ice melt. Others in the field are still contemplating the role of the recent El Niño in Arctic warming, as well as the possibility of a positive feedback existing between low sea ice, sea surface temperatures, and atmospheric temperatures.
For now, Petty has his sights focused on generating a prediction for this September, when Arctic sea ice will presumably reach its minimum yearly extent- all the while remaining aware of the Arctic’s erratic tendencies.
Petty assures, “These things can change. The weather patterns could shift. But I’m watching it on a daily basis to see how it’s doing.”