Antarctic Sea Ice
As air temperature drops in March, seawater begins cooling to
Ice crystals accumulate near the surface.
Within a few days the ice crystals become thin ice surfaces.
This ice thickens and the mass of small pads bump and overlap each other.
Surrounding swells freeze over the pads.
A white surface of ice forms and the ice edge moves outwards by as much as 200 kms a week.
By late winter sea ice covers an area more than double the size of Antarctica.
Chinese ship fails to break out of ice trap in Antarctica after rescue mission
January 04, 2014
The Xue Long Snow Dragon Chinese icebreaker sits in the ice pack unable to get through to the MV Akademik Shokalskiy, in East Antarctica
An attempt to break free of heavy Antarctic ice floes by Chinese icebreaker Xue Long, which helped to rescue passengers from Russia’s Akademik Shokalsky, has failed. But those it helped to rescue are now on their way home on an Australian vessel.
“Xue Long’s attempt to maneuver through the ice early this morning was unsuccessful,” the Australian Maritime Safety Authority (AMSA) said in a statement.
"The ship has confirmed to the Australian Maritime Safety Authority it is beset by ice."
On Thursday, helicopter sent by the Xue Long, or Snow Dragon, successfully evacuated all the 52 passengers aboard the Russian vessel Akademik Shokalsky to the Australian icebreaker Aurora Australis.
Over the next few days there was speculation whether the Chinese ship had gotten stuck as the vessel had hardly moved after its failed attempt to cut through the ice to reach the Shokalsky for the first time.
The Xue Long's movement has been blocked by a drifting kilometer-long iceberg, which constantly changed position and at times came as closely as 1.2 nautical miles (about 2.2 kilometers) to the ship, according to Xinhua reporters aboard the Chinese icebreaker.
Wang Jianzhong, captain of the Xue Long:
“The conditions are extremely complex in this sea area, which is experiencing large astronomical tides, and the positions of the iceberg and ice floes are changing rapidly.”
Chinese Antarctic vessel Xue Long from the bridge of the Aurora Australis ship off Antarctica, both in the frozen waters
to help rescue a nearby Russian research ship.
Photo of January 2, 2014 provided by Fairfax Media Pool and released by the Australian Antarctic Division.
The captains of both the Shokalsky and Xue Long, which remains stuck just a few kilometers from the Russian icebreaker, agreed they don’t need further help from the Australian icebreaker as they will “provide mutual support to each other,” AMSA reported.
A 22-member crew still remains on board the Russian icebreaker, which has been stuck in the ice nearly 100 nautical miles (185 kilometers) from the French Antarctic base of Dumont d'Urville. There is no threat to their lives, AMSA said.
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Antarctic sea ice extent on September 22 2013 compared to 1981-2010 median depicted by orange curve (NSIDC)
Antarctic sea ice in 2013 has grown to a record large extent for a second straight year, baffling scientists seeking to
understand why this ice is expanding rather than shrinking in a warming world.
Antarctic Ice Shelf melting
Sunday, 24 February 2008
Antarctic glaciers surge to ocean
By Martin Redfern
Rothera Research Station, Antarctica
The UK work is discovering just how fast the ice is moving
UK scientists working in Antarctica have found some of the clearest evidence yet of instabilities in the ice of part of West Antarctica.
If the trend continues, they say, it could lead to a significant rise in global sea level.
The new evidence comes from a group of glaciers covering an area the size of Texas, in a remote and seldom visited part of West Antarctica.
The "rivers of ice" have surged sharply in speed towards the ocean.
David Vaughan, of the British Antarctic Survey, explained: "It has been called the weak underbelly of the West Antarctic Ice Sheet, and the reason for that is that this is the area where the bed beneath the ice sheet dips down steepest towards the interior.
"If there is a feedback mechanism to make the ice sheet unstable, it will be most unstable in this region."
There is good reason to be concerned.
Satellite measurements have shown that three huge glaciers here have been speeding up for more than a decade.
The biggest of the glaciers, the Pine Island Glacier, is causing the most concern.
Julian Scott has just returned from there.
He told the BBC: "This is a very important glacier; it's putting more ice into the sea than any other glacier in Antarctica.
"It's a couple of kilometres thick, its 30km wide and it's moving at 3.5km per year, so it's putting a lot of ice into the ocean."
The team drove its skidoos for thousands of km across the ice
It is a very remote and inhospitable region.
It was visited briefly in 1961 by American scientists but no one had returned until this season when Julian Scott and Rob Bingham and colleagues from the British Antarctic survey spent 97 days camping on the flat, white ice.
At times, the temperature got down to minus 30C and strong winds made work impossible.
At one point, the scientists were confined to their tent continuously for eight days.
"The wind really makes the way you feel incredibly colder, so just motivating yourself to go out in the wind is a really big deal," Rob Bingham told BBC News.
When the weather improved, the researchers spent most of their time driving skidoos across the flat, featureless ice.
"We drove skidoos over it for something like 2,500km each and we didn't see a single piece of topography."
Rob Bingham was towing a radar on a 100m-long line and detecting reflections from within the ice using a receiver another 100m behind that.
The signals are revealing ancient flow lines in the ice.
The hope is to reconstruct how it moved in the past.
Julian Scott was performing seismic studies, using pressurised hot water to drill holes 20m or so into the ice and place explosive charges in them.
He used arrays of geophones strung out across the ice to detect reflections, looking, among other things, for signs of soft sediments beneath the ice that might be lubricating its flow.
The Pig Pine Island Glacier is a major draining feature on the Wais
He also placed recorders linked to the global positioning system (GPS) satellites on the ice to track the glacier's motion, recording its position every 10 seconds.
Throughout the 1990s, according to satellite measurements, the glacier was accelerating by around 1% a year.
Julian Scott's sensational finding this season is that it now seems to have accelerated by 7% in a single season, sending more and more ice into the ocean.
"The measurements from last season seem to show an incredible acceleration, a rate of up to 7%. That is far greater than the accelerations they were getting excited about in the 1990s."
The reason does not seem to be warming in the surrounding air.
One possible culprit could be a deep ocean current that is channelled onto the continental shelf close to the mouth of the glacier.
There is not much sea ice to protect it from the warm water, which seems to be undercutting the ice and lubricating its flow.
Julian Scott, however, thinks there may be other forces at work as well.
Much higher up the course of the glacier there is evidence of a volcano that erupted through the ice about 2,000 years ago and the whole region could be volcanically active, releasing geothermal heat to melt the base of the ice and help its slide towards the sea.
Geothermal activity may be playing its part, says Julian Scott
David Vaughan believes that the risk of a major collapse of this section of the West Antarctic ice sheet should be taken seriously.
"There has been the expectation that this could be a vulnerable area," he said.
"Now we have the data to show that this is the area that is changing. So the two things coinciding are actually quite worrying."
The big question now is whether what has been recorded is an exceptional surge or whether it heralds a major collapse of the ice. Julian Scott hopes to find out.
"It is extraordinary and we've left a GPS there over winter to see if it is going to continue this trend."
If the glacier does continue to surge and discharge most of it ice into the sea, say the researchers, the Pine Island Glacier alone could raise global sea level by 25cm.
That might take decades or a century, but neighbouring glaciers are accelerating too and if the entire region were to lose its ice, the sea would rise by 1.5m worldwide.
|MMVIII|Above BBC article is about West Antarctica Ice Shelf melting
Below is explanation of how sea ice, which grows and diminishes each year, benefits all life
Salt is rejected as sea ice forms, increasing the salinity and density of the underlying water.
The magnitude of sea ice release of salt produces a vertical process that conveys higher oxygenated water to lower depths.
This provides a nutrient salt and oxygen rich base for benthic life, as well as contributing to the thermohaline circulation.
Phytoplankton, both inside and underneath the sea ice, are able to photosynthesize as light shines through.
This ‘grass of the sea’ assimilates carbon dioxide in its creation of organic compounds.
It produces food and oxygen for a host of creatures from bacteria to purple and red pteropods, to winged free-swimming molluscs, to copepods and amphipods.
Summer and winter, phytoplankton algae are the energy and oxygen producers at the base of the food web.
Krill and krill lava graze at the bottom of the pack ice, feeding on the microscopic phytoplankton.
Krill transparent shrimp like crustaceans have small bright red pigment spots on their shell.
They also play a key role in the Antarctic food web.
In springtime with the melting of ice there is a typical intense blooming of phytoplankton along the edges of ice retreat.
Krill feed on this algae and are found in great abundance.
When the Baleen whale almost went extinct in the southern oceans due to human capture, the amount of krill made available caused some penguin populations to explode.
Commercial fishing of krill began in the early 1970s.
The crustaceans are processed on board trawlers into food for human consumption, food for farm animals, and food for farmed fish.
Japan, Ukraine, Russia, USA, Poland, Argentina, the Republic of Korea, South Africa and Uruguay fish krill.
Canada and the UK have stated their intention to fish.
Because whales, seals, penguins, seabirds, fish and squid depend directly or indirectly on krill, the Convention on the Conservation of Antarctic Marine Living Resources was enacted in 1981.
The fishing treaty the treaty also applies to the recovery of whales and some overexploited species of fish had as its aim the protection of krill from the consequences of rapidly expanding fishing.
Today many species of Penguins are declining in population, especially on the outer islands of the peninsula.
Since 1989, Chinstrap and Adélie numbers have fallen by 35 percent and 40 percent respectively on King George Island.
There are some studies to show that krill are no longer in such abundance due to the loss of winter sea ice in these areas.
Satellites started measuring the sea ice in 1973.
Over the last 18 years the mean position of the Antarctic sea ice edge has remained constant, but around the Antarctic Peninsula the ice pack has been shrinking.
Pack ice is the resting and breeding grounds of Adélie, Crabeater and Emperor penguins.
Weddell, and Leopard seals also use the pack ice as resting and breeding places.
Seal pups and their mothers hunt in the breaks in sea-ice for food.
Birds follow the ice edge.
Sea birds such as skua, and snow and giant petrel scout in the open spots of sea ice for whatever they might find to eat.
Many scientists believe that due to the way the food chain has adapted, without the winter pack ice there would be much less life in the southern seas at any time of the year.
The surrounding oceans, sea ice and the atmosphere, form a complex interactive system.
Sea ice insulates the relatively warm ocean water from the cold polar atmosphere.
It also helps to refract light rays from the sun, lessening temperature increase.
Through its phytoplankton it absorbs CO2 from the ocean, allowing the ocean to become a sink for additional atmospheric carbon dioxide.
Covering an area of 20 million square kilometers in winter, the Antarctic’s sea ice plays a major role in climate stability.
Space borne Imaging and X-Band Radar is part of NASA’s Mission to Planet Earth.
Measurements of sea ice are being taken daily by NOAA satellite.
Continue with Antarctic Load Master file