See how Arctic sea ice is losing its bulwark against warming summers

See how Arctic sea ice is losing its bulwark against warming summers
Credits: NASA'S Scientific Visualization Studio

Arctic sea ice, the vast sheath of frozen seawater floating on the Arctic Ocean and its neighboring seas, has been hit with a double whammy over the past decades: as its extent shrank, the oldest and thickest ice has either thinned or melted away, leaving the sea ice cap more vulnerable to the warming ocean and atmosphere.

"What we've seen over the years is that the older ice is disappearing," said Walt Meier, a sea ice researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "This older, thicker ice is like the bulwark of sea ice: a warm summer will melt all the young, thin ice away but it can't completely get rid of the older ice. But this older ice is becoming weaker because there's less of it and the remaining old ice is more broken up and thinner, so that bulwark is not as good as it used to be."

Direct measurements of are sporadic and incomplete across the Arctic, so scientists have developed estimates of sea ice age and tracked their evolution from 1984 to the present. Now, a new NASA visualization of the age of Arctic sea ice shows how sea ice has been growing and shrinking, spinning, melting in place and drifting out of the Arctic for the past three decades.

"Ice age is a good analog for ice thickness because basically, as ice gets older it gets thicker," Meier said. "This is due to the ice generally growing more in the winter than it melts in the summer."

In the early 2000s, scientists at the University of Colorado developed a way to monitor Arctic sea ice movement and the evolution of its age by using data from a variety of sources, but primarily satellite passive microwave instruments. These instruments gauge brightness temperature: a measure of the microwave energy emitted by sea ice that is influenced by the ice's temperature, salinity, surface texture and the layer of snow on top of the sea ice. Each floe of sea ice has a characteristic brightness temperature, so the researchers developed an approach that would identify and track ice floes in successive passive microwave images as they moved across the Arctic. The system also uses information from drifting buoys as well as weather data.

Arctic sea ice has not only been shrinking in surface area in recent years, it's becoming younger and thinner as well. In this animation, where the ice cover almost looks gelatinous as it pulses through the seasons, cryospheric scientist Dr. Walt Meier of NASA Goddard Space Flight Center describes how the sea ice has undergone fundamental changes during the era of satellite measurements. Credit: NASA's Goddard Space flight Center/Jefferson Beck

"It's like bookkeeping; we're keeping track of sea ice as it moves around, up until it melts in place or leaves the Arctic," said Meier, who is a collaborator of the group at the University of Colorado and the National Snow and Ice Data Center in Boulder, Colorado, the center that currently maintains the Arctic sea ice age data.

Ice in motion

Every year, sea ice forms in the winter and melts in the summer. The sea ice that survives the melt season thickens with each passing year: newly formed ice grows to about 3 to 7 feet of thickness during its first year, while multi-year ice (sea ice that has survived several melt seasons) is about 10 to 13 feet thick. The older and thicker ice is more resistant to melt and less likely to get pushed around by winds or broken up by waves or storms.

The motion of sea ice is not limited to its seasonal expansion and shrinkage: Except for coastal regions where sea ice is attached to the shore, the sea ice cap is in almost constant movement. The primary driver of sea ice movement in the Arctic is wind and there are two major features in the Arctic circulation: the Beaufort Gyre, a clockwise ice circulation that makes ice spin like a wheel in the Beaufort Sea, north of Alaska, and the Transpolar Drift Stream, which transports ice from Siberia's coast toward the Fram Strait east of Greenland, where the ice exits the Arctic basin and melts in the warmer waters of the Atlantic Ocean.

"On a week-to-week basis, there are weather systems that come through, so the ice isn't moving at a constant rate: sometimes the Beaufort Gyre reverses or breaks down for a couple weeks or so, the Transpolar Drift Stream shifts in its direction ... but the overall pattern is this one," Meier said. "Then the spring melt starts and the ice shrinks back, disappearing from the peripheral seas."

The new animation shows two main bursts of thick ice loss: the first one, starting in 1989 and lasting a few years, was due to a switch in the Arctic Oscillation, an atmospheric circulation pattern, which shrank the Beaufort Gyre and enhanced the Transpolar Drift Stream, flushing more sea ice than usual out of the Arctic. The second peak in ice loss started in the mid-2000s.

"Unlike in the 1980s, it's not so much as ice being flushed out -though that's still going on too," Meier said. "What's happening now more is that the old ice is melting within the Arctic Ocean during the summertime. One of the reasons is that the multiyear ice used to be a pretty consolidated ice pack and now we're seeing relatively smaller chunks of old ice interspersed with younger ice. These isolated floes of thicker ice are much easier to melt."

"We've lost most of the older ice: In the 1980s, multiyear ice made up 20 percent of the sea ice cover. Now it's only about 3 percent," Meier said. "The older ice was like the insurance policy of the Arctic sea ice pack: as we lose it, the likelihood for a largely ice-free summer in the Arctic increases."


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Citation: See how Arctic sea ice is losing its bulwark against warming summers (2016, October 28) retrieved 15 September 2019 from https://phys.org/news/2016-10-arctic-sea-ice-bulwark-summers.html
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Oct 28, 2016
My solution to create a global cold forcing in the Arctic to forestall the inevitable is to dam Bering Straits to 1/100 its flow to create a year-round sea-ice refuge using modified Dutch levee & dam methods for deeper water learning & refining by raising and restoring villages being lost till ready.

Then build a weir dam & shipping locks at St. Lawrence Island, with reduced flow then to build ice-polders protecting sections to allow the bottom to refreeze and prevent shipping or warmer freshwater too far from shore, confining both.

If that works to build atolls around the methane flares to refreeze them, this may be fast the bubbles make a rising flow and bring in colder water at the sides.

The ice-polders and larger areas calmed by levee sections and shoals to attempt to sustain ice much longer in half the Bering Sea, all of the Chukchi Sea, farther south in the Bering & north into the Beaufort the goal.

This will have an effect on the jetstreams, hasn't been modelled.

Oct 29, 2016
A simple phenomenon is the temperature Cold. All cells, quarks, nuclei, blood, earth etc produce cold from their poles. The ratio of cold emitting from cells is so minute as to go unnoticed except of course the big cell Earth. Every cell has a nucleus with orbiting bits of itself (nuclei) and individually con zillions of these are in harmony with the cell until a reaction causes the particles to repel one another. Individually these particles have the same energy as the parent two poled cell. Now you will notice the cold being produced. As an example take an air cell and cause a reaction! OK just blow on your hand.

COOL experiment
Fill a stubby clear water glass - full of water. Place in the freezer. Next day drill a - inch hole down into the center of ice. Fill that hole with water then put it into the fridge (not freezer). After a couple hours you will notice that water surrounds the berg

Oct 29, 2016
By the by one quarter inch is the size to drill. The same phenomenon as the ice cube takes place at Earths poles keeping the ice frozen.

Ice of the arctic is one big fridge creating its own cold. It will be when all hell freezes over that a little warmth will affect these ice packs. What does affect the melting of these ice packs are erratic radiation blasts, the same that are causing erratic Earth tippings.

The ice packs around the world (perma frost) have received jolts of radiation causing internal rot (melting)! Cold of winter does not penetrate this now rotten ice.

Oct 29, 2016
After a couple hours you will notice that water surrounds the berg and the drilled hole of water is frozen solid.

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