Arctic sea ice has reached its minimum extent for 2018, according to scientists at the National Snow and Ice Data Center.
At 4.59 million square kilometers (1.77 million square miles), it ties with 2008 and 2010 for the sixth lowest minimum in the nearly 40-year satellite record.
“It’s a fair amount above our record low, which was a really extreme year in 2012, but it’s much lower than what used to be normal conditions in the ’80s and ’90s,” said Walt Meier who analyzes sea ice for the National Snow and Ice Data Center in Colorado.
The Arctic used to be cold enough that huge portions of the ice on the Arctic Ocean would remain throughout summer, creating what’s called “multi-year ice.”
“We’re taking an area that was basically the size of the lower 48 United States that was continuously ice-covered even through the summer,” said Meier. “Now we’ve lost basically about half of that ice cover… half that’s open ocean at the end of summer.”
That’s a striking image: an ice country on the scale of the lower 48 that’s been cut nearly in half as the Arctic has warmed. The borders of that country are essentially what the “ice minimum” is a measure of.
Meier says the Arctic has been losing upwards of 13% of that area each decade.
Ice reflects most of the energy that reaches it from the sun, while water traps and holds it. So the more ice is replaced by open water, the more heat is added to the Arctic. And what happens in the Arctic, doesn’t stay in the Arctic says Meier.
“The Arctic’s like an air conditioner or refrigerator for the global climate,” said Meier. “And as the Arctic warms, partly because the sea ice is going away, it’s like you’re opening that refrigerator door… we’re losing that cooling ability.”
Meier says that some scientists also see indications that a warming Arctic is affecting the polar jet stream, a current of wind above the earth that can affect seasonal weather patterns. He says it could be part of what explains increasing frequency and severity of certain weather events like droughts, heat waves and heavy rains.
When NSIDC does its final analysis in a few months, the sea ice minimum could change slightly. Meier says that they generally see the number in the final analysis change by less than 0.05 million square kilometers, but since the 2018 number was so close to 2008 and 2010, it’s possible it could change the ranking.
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