September, you see, is when Arctic sea ice naturally declines to its annual minimum each year, after months of summer warmth and unbroken sunlight. No wonder, then, that climate wonks have been anxiously watching the daily charts from the National Snow and Ice Data Center (NSIDC) recently, wondering how low this September’s ice would actually go.
However, Arctic weather during the summer was more friendly to ice — cloudiness, for instance, can cool down the ocean — and as a result, this year’s September extent wasn’t quite so low as in 2012. Instead, the National Snow and Ice Data Center announced Thursday that 2016 was merely tied for the second-lowest extent ever recorded, with the year 2007.
The all-time record low year, 2012, saw just 1.31 million square miles of sea ice extent at its September low, on Sept. 17 of that year. The 2016 low, reached on Sept. 10, was 1.6 million square miles, and the 2007 low was very nearly the same, leading to what the center calls a “statistical tie.”
In other words, in September of 2007 and 2016, the area of the Arctic Ocean covered by sea ice was bigger than it was in 2012 by an area about the size of Texas.
But the real story is that all of these years are way, way below the average, as a figure from the National Snow and Ice Data Center makes clear:
The center stresses that its determination about 2016’s sea ice minimum is merely “preliminary.” It is still possible that the sea ice extent could tick a bit lower before the ocean begins to refreeze, and the planet’s icy cap starts to expand, as winter nears.
The researchers actually appeared to express a bit of surprise that 2016 didn’t stand out more in September, given how dramatically low ice extent was earlier in the year, and given evidence that the ice was also very thin and the ocean very warm.
After all, 2016 is widely expected to turn out to be the warmest year on record for the globe as a whole.
But sea ice doesn’t necessarily follow in perfect lockstep. Weather conditions during the summer matter a lot: “Statistically, there is little relationship between May and September sea ice extents after removing the long-term trend, indicating the strong role of summer weather patterns in controlling sea ice loss,” notes the NSIDC.
Thus, the punchline is clear: Don’t focus too much on any individual year; focus instead on the trend. And when it comes to trends in Arctic sea ice — one of the most observable planetary indicators — there’s just no doubt that the trend is down, and down, and down, even if not every year sets a new record.
“September Arctic sea ice is now declining at a rate of 13.4 percent per decade, relative to the 1981 to 2010 average,” NASA says.
Or think about it another way: According to a table presented by the NSIDC, all of the 10 lowest years for Arctic sea ice extent have occurred since 2005.
This year, Arctic sea ice melt was paired with an astonishing window on the kind of world that this will bring — a cruise ship, the Crystal Serenity, successfully navigated the Northwest Passage on a trip from Alaska to New York via the Arctic. As sea ice trends lower and lower, we can only expect such incursions to grow.
“The loss of summer sea ice … opens up the Arctic to increasing vessel traffic and the risks that come with it like higher risk of oil spills, impact of noise pollution on marine wildlife and the introduction of invasive species,” said Janice Searles Jones, president of the Ocean Conservancy, in a statement. “By 2025, vessel traffic through the Bering Strait is projected to increase anywhere from 100 – 500% from what it was in 2013.”
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