Wintertime Arctic sea ice growth slows long-term decline

Wintertime arctic sea ice growth slows long-term decline: NASA
he sun setting over the Arctic sea ice pack, as observed during the Beaufort Gyre Exploration Project in October 2014. Credit: NASA/Alek Petty

New NASA research has found that increases in the rate at which Arctic sea ice grows in the winter may have partially slowed down the decline of the Arctic sea ice cover.

As temperatures in the Arctic have warmed at double the pace of the rest of the planet, the expanse of frozen seawater that blankets the Arctic Ocean and neighboring seas has shrunk and thinned over the past three decades. The end-of-summer Arctic sea ice extent has almost halved since the early 1980s. A recent NASA study found that since 1958, the Arctic sea ice cover has lost on average around two-thirds of its thickness and now 70 percent of the sea ice cap is made of seasonal ice, or ice that forms and melts within a single year.

But at the same time that sea ice is vanishing quicker than it has ever been observed in the satellite record, it is also thickening at a faster rate during winter. This increase in might last for decades, a new study accepted for publication in Geophysical Research Letters found.

This does not mean that the ice cover is recovering, though. Just delaying its demise.

"This increase in the amount of sea ice growing in winter doesn't overcome the large increase in melting we've observed in recent decades," said Alek Petty, a sea ice scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study. "Overall, thickness is decreasing. Arctic sea ice is still very much in decline across all seasons and is projected to continue its decline over the coming decades. "

Petty and his team used and observations of sea ice thickness from the European Space Agency's CryoSat-2 satellite to explore sea ice growth variability across the Arctic. The climate model results compared well both with CryoSat-2's measurements and the results of another commonly used Arctic sea ice model, giving the authors confidence in the climate model's ability to capture Arctic sea ice variability.

"The global climate model seems to do a good job of capturing the Arctic sea ice state and shows that most of the thickness change in the central Arctic is from thermodynamics, that is, ice formation and ice melt, although around the Arctic sea ice edge dynamics, which is ice transport, can play a bigger role," Petty said.

These model simulations showed that in the 1980s, when Arctic sea ice was on average 6.6 feet thick in October, about 3.3 extra feet of ice would form over the winter. That rate of growth has increased and may continue to do so for several more decades in some regions of the Arctic; in the coming decades, we could have an ice pack that would on average be only around 3.3 feet thick in October, but could experience up to 5 feet of ice growth over the winter.

It seems counterintuitive: how does a weakening ice cover manage to grow at a faster rate during the winter than it did when the Arctic was colder and the ice was thicker and stronger?

"Our findings highlight some resilience of the Arctic sea ice cover," Petty said. "If we didn't have this negative feedback, the ice would be declining even faster than it currently is. Unfortunately, the positive feedback loop of summer ice melt and increased solar absorption associated with summer ice melting still appears to be dominant and continue to drive overall sea ice declines."

Nonetheless, the increased rate of sea ice thickening in winter has other implications. As ice forms at the , it releases a lot of the salty and dense water from which it originated, which sinks and increases the mixing of waters in the upper ocean. The more ice formation that takes place, the more mixing we expect to see in the upper ocean. Increases in this ice formation and mixing during winter may help mitigate the strong freshening of the Arctic Ocean's surface waters that has been observed in recent decades due to increased summer melt.

"This is altering the seasonal balance and the salinity distribution of the upper ocean in the Arctic; it's changing when we have fresh water, when we have salty water and how deep and seasonal that upper oceanic mixed layer is," Petty said. "And that's all going to mean that local micro-organisms and ecosystems have to adapt to these rapidly evolving conditions."

Petty's projections found that, by the middle of the century, the strong increases in atmospheric and oceanic temperatures will outweigh the mechanism that allows ice to regrow faster, and the Arctic sea ice cover will decline further. The study predicted that the switch will happen once the sea ice is less than 1.6 feet thick at the beginning of , or its concentration -the percentage of an area that is covered in sea ice- is less than 50 percent.

"This mechanism increasing ice growth is unlikely to be sufficient in preventing an ice-free Arctic this century," Petty and his colleagues concluded.


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With thick ice gone, Arctic sea ice changes more slowly

Journal information: Geophysical Research Letters

Citation: Wintertime Arctic sea ice growth slows long-term decline (2018, December 6) retrieved 18 June 2019 from https://phys.org/news/2018-12-wintertime-arctic-sea-ice-growth.html
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User comments

Dec 07, 2018
"This does not mean that the ice cover is recovering, though. Just delaying its demise."
Fortune-tellers are now employed in the Climate Change game?


Dec 08, 2018
I make that four SEU
triple post

Quadruple post

That ice
that
is
at its triple point
of .01 degree
is at its most slippery
so take care
one and all
as the sherry flows
as the fruit cakes multiplieth
in this festive time
as and when
the ice cometh
take
a
lesson from this quadrupole triple toe loop
we dinosaurs will simply slip
In its triple point

Dec 09, 2018
"This does not mean that the ice cover is recovering, though. Just delaying its demise."
Fortune-tellers are now employed in the Climate Change game?

No. These predictions are as a result of something called "science" that is done by people a lot smarter than you or I and who that have spent YEARS doing intensive research on it thus, unsurprisingly, know many things about it that you and I don't.

So who's predictions we should give greater trust to by default? -the scientist, you know, as in the people that actually know something about what they are talking about? -or the usual loonies that don't know the first thing about the science but have formed there own idiotically opposing opinions on it anyway with the WILDLY delusional arrogance that they mysteriously actually know better than the scientists? I assert it should be the former.


Dec 09, 2018
but , but , 2018 is the HOTTEST yr ever !!!!

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