Friday, January 6, 2017

Just in Case You're Getting Complacent about Climate Change

Giant iceberg poised to break off from Antarctic shelf

Predicted to be one of the largest break-offs ever recorded, separation of iceberg could trigger breakup of most northern major ice shelf, Larsen C

The Guardian  Hannah Devlin Science correspondent  6 January 2017

A giant iceberg, with an area equivalent to Trinidad and Tobago, is poised to break off from the Antarctic shelf.

A thread of just 20km of ice is now preventing the 5,000 sq km mass from floating away, following the sudden expansion last month of a rift that has been steadily growing for more than a decade.

The iceberg, which is positioned on the most northern major ice shelf in Antarctica, known as Larsen C, is predicted to be one of the largest 10 break-offs ever recorded.

Professor Adrian Luckman, a scientist at Swansea University and leader of the UK’s Midas project, said in a statement: “After a few months of steady, incremental advance since the last event, the rift grew suddenly by a further 18km during the second half of December 2016. Only a final 20km of ice now connects an iceberg one quarter the size of Wales to its parent ice shelf.”

The separation could trigger a wider break-up of the Larsen C ice shelf. Photograph: Midas Project, A Luckman, Swansea University

The separation of the iceberg “will fundamentally change the landscape of the Antarctic Peninsula” and could trigger a wider break-up of the Larsen C ice shelf, he added.

“If it doesn’t go in the next few months, I’ll be amazed,” Luckman told BBC News.

Ice shelves are vast expanses of ice floating on the sea, several hundred metres thick, at the edge of glaciers.

Scientists fear the loss of ice shelves will destabilise the frozen continent’s inland glaciers. And while the splitting off of the iceberg would not contribute to rising sea levels, the loss of glacial ice would.

Martin O’Leary, also of Swansea University, said: “It just makes the whole shelf less stable. If it were to collapse there would be nothing holding the glaciers up and they would start to flow quite quickly indeed.”

O’Leary added that while calving is a natural process that happens every decade or so and is not driven by climate change, the disintegration of a major shelf could accelerate the melting of glacial ice linked to warming oceans.

Several ice shelves have cracked up around northern parts of Antarctica in recent years, including the Larsen B that disintegrated in 2002.

“We have previously shown that the new configuration will be less stable than it was prior to the rift, and that Larsen C may eventually follow the example of its neighbour Larsen B, which disintegrated in 2002 following a similar rift-induced calving event,” the Midas project website said.

The scientists predict that when the vast chunk of ice eventually breaks away it will drift gently out to sea, with smaller pieces splintering off. “It would be a very dramatic event if you were standing next to it, but probably not in the grand scheme of things,” said O’Leary.
British Antarctic research station to be moved due to deep crack in the ice
Dormant chasm has opened up and risks cutting the station off from the rest of the ice shelf

The British Antarctic Survey’s Halley VI research station has recorded records data relevant to space weather, climate change, and atmospheric phenomena since 2012. Photograph: British Antarctic Survey

The Guardian  Elle Hunt  7 December 2016

Britain is preparing to move its research station in the Antarctic 23km further inland because it is under threat from a growing crack in the ice.

The British Antarctic Survey’s Halley VI research station has recorded data relevant to space weather, climate change, and atmospheric phenomena from its site on the Brunt Ice Shelf shelf since 2012.

However, due to a growing chasm about 7km (4.3 miles) away that risks cutting the station off from the rest of the shelf, officials have announced that base will have to be moved.

The new site, nicknamed Halley VI A, was identified during in-depth site surveys in the 2015-16 Antarctic summer. Now that winter has passed, the relocation team are preparing to tow the station 23km to its new home using large tractors.

Though the station has not been moved from its present location since it was taken there from its construction site in 2012, it was designed with potential relocation in mind to accommodate movement in the ice.

Tim Stockings, director of operations at British Antarctic Survey, said in a statement the team was “excited by the challenge”, and minimising disruption to science programmes was a priority.

“Antarctica can be a very hostile environment. Each summer season is very short, about nine weeks.

And because the ice and the weather are unpredictable we have to be flexible in our approach.”

Map of the Halley IV Research Station Photograph: British Antarctic Survey 

In 2012, satellite monitoring revealed the first signs of movement in a chasm in the ice shelf that had lain dormant for at least 35 years. Glaciologists have since determined the most likely path and speed of the crack, and monitoring is ongoing.

Parts of the ice shelf irregularly cleave off from the ice sheet, creating icebergs. It is not known if the growth of the crack is related to global warming. 

In October, a second crack emerged in the ice about 17km north of the station, across a route sometimes used to resupply the base. Alternative paths have been used since.

The planned move will be completed in stages over a period of three years, allowing scientific research to continue in temporary facilities at Halley at the existing site.

The station’s eight modules will eventually be unattached and moved inland across the ice by tractor. Operations will then be moved to the new location next season.

The relocation should be completed by 6 April 2018.

Ozone measurements have been recorded continuously at Halley since 1956, and led to the discovery of the Antarctic ozone hole in 1985. Space weather data is also captured there daily.

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