• Sat. Oct 24th, 2020

Dimancherouge

Technology

Arctic sea ice hits second-lowest level on record amid Siberian heat, fires

Because of the outsize effects of climate change in the Far North, the Arctic is likely to be seasonally ice-free within two to three decades, according to NSIDC Director Mark Serreze.

The NSIDC declared Monday that the likely sea ice annual minimum was reached Sept. 15, when sea ice reached 1.44 million square miles, though it’s possible that a shift in weather patterns could cause some further melting.

The sea ice minimum was 135,000 square miles above the record low in 2012 but a staggering 969,000 square miles below the 1981-2010 average seasonal low, the size of which is equivalent to the states of Alaska, Texas and Montana combined.

Because of rapid Arctic climate change — the region is warming at about three times the rate of the rest of the globe — the downward trend in the minimum ice extent during the past 42 years is 13.4 percent per decade, compared with the 1981-2010 average. The 14 years with the lowest extents in the satellite era have all occurred in the past 14 years, the NSIDC found.

In the Arctic, climate feedbacks are accelerating warming and leading to rapid climate shocks that are reverberating outside the Far North. For example, as air temperatures warm and sea ice melts, it exposes darker ocean waters. These waters absorb more solar radiation, which warms the sea, melts more ice, increases air temperatures and continues the cycle.

According to Serreze, the ice cover north of Siberia entered the summer melt season in a vulnerable position. This sea ice was thinner than average because of prevailing offshore winds in that region throughout the winter that exported thicker ice floes to the north, across the top of the planet.

Then, when the relentless and extreme heat struck the Siberian Arctic during the summer, the thinner ice cover quickly melted. Temperatures across the Arctic were unusually high this summer, with May, June, July and August setting records for either the warmest or second-warmest such months on record since at least 1979.

“These heat waves are getting hotter, and the cold waves are not as cold,” Serreze said in an interview.

This melt season featured record-breaking Arctic wildfires in the Siberian Arctic, with concerns raised about melting permafrost, which acts like a greenhouse gas bank by keeping these gases locked away in the frozen soil.

When permafrost melts, it’s like tapping into the savings account, releasing planet-warming greenhouse gases back into the atmosphere.

The prolonged Siberian heat, which began in January and kicked into high gear during the summer, had clear links to global warming, according to a recent study. Researchers reported that the prolonged January-June heat in northern Siberia was made at least 600 times more likely by human-caused climate change. This led them to conclude that such an event would be nearly impossible in the absence of global warming.

Julienne Stroeve, a senior scientist at the NSIDC, said 2020′s sea ice minimum is cause for concern, given that “what happens in the Arctic doesn’t stay in the Arctic.”

“Everything is interconnected, so removing the reflective ice cover allows the Arctic to warm up even faster, with impacts on permafrost thaw, Greenland and glacier melt, large-scale ocean and atmospheric circulation patterns,” she wrote in an email.

In addition to Siberia, other parts of the Arctic were record-warm. In Longyearbyen, Svalbard, the northernmost inhabited settlement and part of Norway, temperatures soared to 71.1 degrees (21.7 Celsius) on July 25, setting a record high for that location.

According to Zack Labe, a postdoctoral researcher in atmospheric sciences at Colorado State University who keeps close tabs on Arctic warming, the northernmost reaches of the Arctic did see record-low sea extent this season.

The main reason that the sea ice extent did not reach a record low for the entire Arctic, NSIDC data shows, is that somewhat thicker, older sea ice failed to diminish significantly in the Beaufort Sea, located north of Alaska. While the overall trend in sea ice extent and thickness is downward, there is considerable variability from year to year based on weather conditions, Serreze said.

He says people should take this summer melt season as another warning sign that human activities, mainly the burning of fossil fuels for energy, are pushing the climate into uncharted territory. “We knew this would happen. … We knew this was coming, and here it is. … Maybe you should start listening to the scientists,” he said.

Serreze said a seasonally ice-free Arctic will have broad ramifications, from increased shipping, a trend already occurring along the Northern Sea Route in particular, to ecological shifts in the Arctic Ocean that could imperil iconic species that depend on the ice cover.

“That is a fundamentally different Arctic,” he said. “I think the ramifications are extreme.”

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