from the breaking-bad dept.
A one trillion tonne iceberg – one of the biggest ever recorded - has calved away from the Larsen C Ice Shelf in Antarctica. The calving occurred sometime between Monday 10th July and Wednesday 12th July 2017, when a 5,800 square km section of Larsen C finally broke away. The iceberg, which is likely to be named A68, weighs more than a trillion tonnes. Its volume is twice that of Lake Erie, one of the Great Lakes.
Complete Calving Coverage:
Antarctic Larsen C Ice Shelf to Calve; Halley VI Research Station Plans Move
Antarctic Ice Rift Close to Calving, After Growing 17km in 6 Days
Delaware-Sized Iceberg Could Break Off of Antarctica at Any Moment
Larsen C Rift Branches as it Comes Within 5 km of Calving
According to a December 1st article from NASA:
On Nov. 10, 2016, scientists on NASA's IceBridge mission photographed an oblique view of a massive rift in the Antarctic Peninsula's Larsen C ice shelf....
The IceBridge scientists measured the Larsen C fracture to be about 70 miles [113 km] long, more than 300 feet [91 m] wide and about a third of a mile [a half of a kilometer] deep. The crack completely cuts through the ice shelf but it does not go all the way across it – once it does, it will produce an iceberg roughly the size of the state of Delaware.
The British Antarctic Survey's Halley VI research station is currently located on the Larsen C ice shelf. Fortunately, the station was designed to move. A December 7th article from The Guardian gives more information about that station and the upcoming move:
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....
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 [14 miles] to its new home using large tractors.
The Telegraph outlines the timeframe for the move:
In 2012, satellite monitoring of the ice shelf revealed the first signs of movement in the chasm that had lain dormant for at least 35 years and, by 2013, it began opening at an alarming pace of one mile per year. If the base does not move, it could be in danger of tumbling into the chasm by 2020.
To make matters more time critical, in October, a new crack emerged 10 miles [16 km] to the north of the research station across the route sometimes used to resupply the base.
The team has just nine weeks to relocate operations, before the harsh winter begins, making it difficult to move the structure amid complete darkness, plummeting temperatures and gale-force winds.
Additional information about the Halley VI research station is available from the British Antarctic Survey.
The rift in the Larsen C ice shelf in Antarctica has grown by 17km in the last few days and is now only 13km from the ice front, indicating that calving of an iceberg is probably very close, Swansea University researchers revealed after studying the latest satellite data.
The rift in Larsen C is likely to lead to one of the largest icebergs ever recorded. It is being monitored by researchers from the UK's Project Midas, led by Swansea University.
Professor Adrian Luckman of Swansea University College of Science, head of Project Midas, described the latest findings:
"In the largest jump since January, the rift in the Larsen C Ice Shelf has grown an additional 17 km (11 miles) between May 25 and May 31 2017. This has moved the rift tip to within 13 km (8 miles) of breaking all the way through to the ice front, producing one of the largest ever recorded icebergs.
The rift tip appears also to have turned significantly towards the ice front, indicating that the time of calving is probably very close.
The rift has now fully breached the zone of soft 'suture' ice originating at the Cole Peninsula and there appears to be very little to prevent the iceberg from breaking away completely."
Researchers say the loss of a piece a quarter of the size of Wales will leave the whole shelf vulnerable to future break-up.
Larsen C is approximately 350m thick and floats on the seas at the edge of West Antarctica, holding back the flow of glaciers that feed into it.
Professor Luckman added, "When it calves, the Larsen C Ice Shelf will lose more than 10% of its area to leave the ice front at its most retreated position ever recorded; this event will fundamentally change the landscape of the Antarctic Peninsula.
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 will continue to monitor the development of the rift and assess its ongoing impact on the ice shelf. Further updates will be available on our blog (projectmidas.org),and on our Twitter feed"
The team say they have no evidence to link the growth of this rift, and the eventual calving, to climate change. However, it is widely accepted that warming ocean and atmospheric temperatures have been a factor in earlier disintegrations of ice shelves elsewhere on the Antarctic Peninsula, most notably Larsen A (1995) and Larsen B (2002).
They point out that this is one of the fastest warming places on Earth, a feature which will certainly not have hindered the development of the rift in Larsen C.
-- submitted from IRC
A deep crack on on Antarctica's Larsen C ice shelf has nearly severed off one of the largest icebergs ever recorded:
One of the largest icebergs ever recorded — 2,500 square miles, about the size of Delaware — is about to break off Antarctica, according to the European Space Agency. The iceberg could speed up the break-off of other ice chunks, eventually eating away at a barrier that prevents ice from flowing to the sea.
The impending iceberg is being carved from one of the continent's major ice shelves, called Larsen C. Scientists have been monitoring Larsen C for months now, as a deep crack has slowly extended over the course of 120 miles. Only about three miles of ice are keeping the iceberg attached to the shelf, ESA says. No one knows when it will break off — it could be any moment — but when it does, the iceberg will likely be 620 feet thick (about the height of the Waldorf Astoria hotel in New York) and contain roughly 1 trillion tons of ice. It'll be drifting north toward South America, and could even reach the Falkland Islands. "If so it could pose a hazard for ships in Drake Passage," Anna Hogg from the University of Leeds, said in a statement.
Also at BBC.
As the Larsen C ice shelf moves closer to calving one of the largest icebergs on record, there are clear signs of changes in the part of the shelf which is about to calve. In late June 2017, the soon-to-be iceberg tripled in speed, producing the fastest flow speeds ever recorded on Larsen C, and seemed to be on the verge of breaking free.
The latest data from 6th July reveal that, in a release of built-up stresses, the rift branched several times. Using data from ESA’s Sentinel-1 satellites, we can see that there are multiple rift tips now within 5 km of the ice edge. We expect that these rifts will lead to the formation of several smaller icebergs, as well as the large iceberg which we estimate will have an area of 5,800 sq km. Despite this, the iceberg remains attached to the shelf by a thin band of ice. It is remarkable how the moment of calving is still keeping us waiting.
There is a nice animation showing the rift growth since just last year: http://www.projectmidas.org/assets/rift_insar_animation_july.gif
It's finally adrift. When the Larsen C Ice Shelf calved yesterday [Wednesday], it sent one of the largest icebergs ever recorded slipping into a sea frosted with smaller chunks of ice. It marked the end of a decades-long splintering first seen by satellites in the 1960s. The crack stayed small for years until, in 2014, it began racing across the Antarctic ice.
The massive iceberg holds twice as much water used in the United States every year, according to calculations by Peter Gleick of the Pacific Institute. It weighs about 1.1 trillion tons and measures 2,200 square miles. Its volume is twice that of Lake Erie.
"The iceberg is one of the largest recorded, and its future progress is difficult to predict," said Adrian Luckman of Wales' Swansea University, who led a project tracking the crack since 2015. "It may remain in one piece but is more likely to break into fragments. Some of the ice may remain in the area for decades, while parts of the iceberg may drift north into warmer waters."
By mass, the iceberg accounts for 12 percent of the Larsen C Ice Shelf. It's large enough that maps will have to be redrawn. Larsen C was the fourth-largest ice shelf in the world. Now it's the fifth.
In this particular political moment, the calving of a major iceberg has made headlines around the world. Environmental groups connected the event to climate change and the Trump administration's withdrawal from the Paris climate accords. But scientists have cautioned that the story of the iceberg, which will be known as A68, is more nuanced. Climate signals are not clear enough to attribute the event to rising levels of carbon dioxide, but human activity may have contributed to its calving nonetheless.
The ecosystem in between the Larsen Ice Shelf and a giant iceberg is due to be studied:
Scientists will set out in the next week to study an Antarctic realm that has been hidden for thousands of years.
A British Antarctic Survey-led team will explore the seabed ecosystem exposed when a giant iceberg broke away from the Antarctic Peninsula in 2017.
The organisation has also released the first video of the berg, which covers almost 6,000 sq km.
[...] British Antarctic Survey marine biologist Dr Katrin Linse, who is leading the mission, said that the calving of the iceberg, which has been named A68, provides researchers with "a unique opportunity to study marine life as it responds to a dramatic environmental change". "It's important we get there quickly before the undersea environment changes as sunlight enters the water and new species begin to colonise," she explained, adding that the mission was "very exciting".
Also at Live Science.
Related: Antarctic Larsen C Ice Shelf to Calve; Halley VI Research Station Plans Move
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