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Arctic sea ice hits lowest point of the year as planet warms

Scorpio

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Arctic sea ice hits lowest point of the year as planet warms​

By
Alek Petty & Linette Boisvert, NASA

Arctic sea ice reached its minimum extent on September 16. Image courtesy of NASA Earth Observatory/NSIDC


Arctic sea ice reached its minimum extent on September 16. Image courtesy of NASA Earth Observatory/NSIDC

Sept. 23 (UPI) -- September marks the end of the summer sea ice melt season and the Arctic sea ice minimum, when sea ice over the Northern Hemisphere ocean reaches its lowest extent of the year.
For ship captains hoping to navigate across the Arctic, this is typically their best chance to do it, especially in more recent years. Sea ice cover there has dropped by roughly half since the 1980s as a direct result of increased carbon dioxide from human activities.


As NASA scientists, we analyze the causes and consequences of sea ice change. In 2021, the Arctic's sea ice cover reached its minimum extent on Sept. 16. While it wasn't a record low, a look back through the melt season offers some insight into the relentless decline of Arctic sea ice in the face of climate change.
Arctic heating up


In recent years, Arctic sea ice levels have been at their lowest since at least 1850 for the annual mean and in at least 1,000 years for late summer, according to the latest climate assessment from the U.N.'s Intergovernmental Panel on Climate Change. The IPCC concluded that "the Arctic is likely to be practically sea ice free in September at least once before 2050."


As the Arctic's bright ice is replaced by a darker open ocean surface, less of the sun's radiation is reflected back to space, driving additional heating and ice loss. This albedo feedback loop is just one of several reasons why the Arctic is warming about three times faster than the planet as a whole.
Sea ice in 2021


The stage for this year's sea ice minimum was set last winter. The Arctic experienced an anomalous high-pressure system and strong clockwise winds, driving the thickest, oldest sea ice of the Central Arctic into the Beaufort Sea, north of Alaska. Sea ice scientists were taking note.
Summer melt began in earnest in May, a month that also featured multiple cyclones entering the Arctic. This increased sea ice drift but also kept temperatures relatively low, limiting the amount of melt.
The extent and pace of melting increased significantly in June, which featured a predominant low-pressure system and temperatures that were a few degrees higher than average.


By the beginning of July, conditions were tracking very close to the record low set in 2012, but the rate of decline slowed considerably during the second half of the month. Cyclones entering the Arctic from Siberia generated counterclockwise winds and ice drifts. This counterclockwise ice circulation pattern generally reduces the amount of sea ice moving out of the Arctic through the Fram Strait, east of Greenland. This likely contributed to the record low summer sea ice conditions observed in the Greenland Sea.


This ice circulation pattern also increased ice export out of the Laptev Sea, off Siberia, helping create a new record low for early summer ice area in that region. The low-pressure system also increased cloudiness over the Arctic. Clouds generally block incoming solar radiation, reducing sea ice melt, but they can also trap heat lost from the surface, so their impact on sea ice melt can be a mixed bag.
In August, sea ice decline slowed considerably, with warm conditions prevailing along the Siberian coast, but cooler temperatures north of Alaska. The Northern Sea Route -- which Russia has been promoting as a global shipping route as the planet warms -- was actually blocked with ice for the first time since 2008, although ice breaker-supported transits were still very much possible.
At this stage of the melt season, the sea ice pack is at its weakest and is highly responsive to the weather conditions of a given day or week. Subtle shifts can have big impacts. Freak end-of-summer weather events have been linked to the record low sea ice years of 2007 and 2012. "The Great Arctic Cyclone of 2012" is an interesting example.
There's ongoing debate over the effect they have. However, scientists are broadly in agreement that specific storms may not have actually played that big a role in driving the record lows in those years -- things are never that straightforward when it comes to weather and sea ice.


The Arctic sea ice reached its 2021 minimum extent on Sept. 16, coming in at 4.72 million square miles, the 12th lowest on record.
So, the 2021 melt season was, despite all the stops and starts, pretty typical for our new Arctic, with the September minimum ending up slightly higher than what we would have expected from the long-term downward trend. But various new record lows were set in other months and regions of the Arctic.
As the hours of sunlight dwindle over the coming weeks and temperatures drop, Arctic sea ice will start to refreeze. The ice pack will thicken and expand as the surrounding ocean surface temperatures drop toward the freezing point, releasing a lot of the heat that had been absorbed and stored through summer.
This refreeze has started later in recent years, shifting into October and even November. The more heat the ocean gains during summer, the more heat needs to be lost before ice can begin to form again. Because of this, some of the biggest warming signals are actually observed in fall, despite all the attention given to summer ice losses.
Much we don't know
For people living and working in the high Arctic, understanding local ice conditions on a given day or week is what really matters. And predicting Arctic sea ice at these more local scales is even more challenging.


As 2021 demonstrated, sea ice is highly dynamic -- it moves and melts in response to the weather patterns of the day. Think how hard it is for forecasters to predict the weather where you live, with good understanding of weather systems and many observations available, compared to the Arctic, where few direct observations exist.
Weather events can also trigger local feedback loops. A freak heat wave, for example, can trigger ice melt and further warming. Winds and ocean currents also break up and spread ice out across the ocean, where it can be more prone to melt.
Sea ice scientists are hard at work trying to understand these various processes and improve our predictive models. A key missing part of the puzzle for understanding sea ice loss is ice thickness.
Thickness times area equals volume. Like area, sea ice thickness is thought to have halved since the 1980s, meaning today's Arctic ice pack is only about a quarter of the volume it was just a few decades ago. For those hoping to navigate the Arctic Ocean, knowing the thickness of any ice they may encounter is crucial. Sea ice thickness is much harder to measure consistently from space. However, new technologies, like ICESat-2, are providing key breakthroughs.


Despite all this uncertainty, it's looking pretty likely that summer ice-free Arctic conditions are not too far away. The good news is that the path forward is still largely dependent on future emissions, and there is still no evidence the planet has passed a tipping point of sea ice loss, meaning humans are still very much in the driver's seat.Alek Petty is an associate research scientist in polar sea ice variability at NASA, and Linette Boisvert is a sea ice scientist and deputy project scientist for NASA's Operation IceBridge.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The views and opinions expressed in this commentary are solely those of the authors.

 

Scorpio

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The good news is that the path forward is still largely dependent on future emissions, and there is still no evidence the planet has passed a tipping point of sea ice loss, meaning humans are still very much in the driver's seat.

wow, just wow,
the hubris of these people is just too much for me,

humans are in, or have control
 

Cigarlover

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12,000 years ago the oceans were 400' lower and Canada was pretty much all under ice. I would be willing to guess that it wasn't SUV's that were causing this.
 

chieftain

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It's a bullshit counter to the article you posted on Monday Scorp:

 

Uglytruth

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Yet big mike & the kenyans compound is not under water.....
 

Cigarlover

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Yet big mike & the kenyans compound is not under water.....
Bushs place in Kennebunkport is right on the water too. Biden and family members have beach houses on both coasts I believe. Trump has plenty of beach front exposure. At least he didn't buy into the global warming hysteria.
 

gnome

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It's a bullshit counter to the article you posted on Monday Scorp:

Year-to-year fluctuations are weather. The accelerating decline over decades is climate.

Annual rebounds of ice are short lived. New ice is thin and does not replace thicker older ice that previously melted.

arctic_sea_ice_extent_020321.png
 

gnome

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12,000 years ago the oceans were 400' lower and Canada was pretty much all under ice. I would be willing to guess that it wasn't SUV's that were causing this.
Correct, that was caused by orbital tilt. Orbital tilt today exerts a slight cooling influence, so it is not causing current warming.

Blonde hair spread through northern europe about 11,000 years ago. I would be willing to guess it wasn't hair dye that caused this.
Just because natural blondes have been around for thousands of years, does not mean blondes today are all natural.
 

Scorpio

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Voodoo

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It's a bullshit counter to the article you posted on Monday Scorp:


I was going to say, wasn't there just an article saying the opposite. GD statistics.
 

Oldmansmith

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They don't say the opposite, one says 12th lowest ever at lowest point of the year, the other says 25% more than last year. They are not mutually exclusive.
 

KnowWhy

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why do these articles use phrases like “mixed bag” and “freak weather?” Smart people don’t need perfect grammar, but those indicate the author’s grasping to fill space or make stuff up.
mixed bag=no idea
freak=miracle
Please give me numbers and let me guess where we’re going.

The equivalent is the cdc article saying 74% of the sick are fully vaxxed, then recommending vaccinations
 

hardmoney

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Bigfoot

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The people who work for NASA would never cherry pick numbers in order to promote an agenda. These smart nobles will save the Earth from our wood burning stoves and gas powered vehicles. Let us pledge to obey. Thinking is above our pay grade. Hail Gaia! We must atone for our existence.
 

dacrunch

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"A picture is worth 1000 words" is the old saying, right?

G7 Sea Levels 2021 vs 1925.jpg
 

Merkin

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The people who work for NASA would never cherry pick numbers in order to promote an agenda. These smart nobles will save the Earth from our wood burning stoves and gas powered vehicles. Let us pledge to obey. Thinking is above our pay grade. Hail Gaia! We must atone for our existence.
Never?
 

mnmom

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Just a random note.. many geologists and climatologists back in my academic days swore ice ages were started when fresh water melting at the north pole caused the gulf stream to slow and stop. The real news is in the Atlantic multidecadal oscillation and how fresh water from the arctic causes turnover.
 

Thecrensh

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Just a random note.. many geologists and climatologists back in my academic days swore ice ages were started when fresh water melting at the north pole caused the gulf stream to slow and stop. The real news is in the Atlantic multidecadal oscillation and how fresh water from the arctic causes turnover.
That is the theory, and apparently it has happened several times in the past- specifically, around 11,600 years ago during "meltwater pulse 1B" following the younger-dryas event (possibly a meteor or comet strike on the N. American ice sheet).