Two of the world’s largest icebergs – including one the size of Greater London and an even larger one the size of Cornwall – are being tracked by British scientists.
There are concerns that the frozen behemoths are drifting into areas where they could affect shipping, fishing and wildlife.
The huge A81, which is the size of England’s capital, broke away from Antarctica’s Brunt Ice Shelf in late January and has just been photographed for the most part from the air.
Glaciologist Dr Oliver Marsh, who has returned from the British Antarctic Survey’s (BAS) Halley Research Station, said: ‘This was a calving that we knew was coming.
‘BAS has been tracking the Brunt ice shelf and the abysses that have formed over it for more than a decade.
Huge: Two of the world’s largest icebergs – including one the size of Greater London (pictured) and an even bigger one the size of Cornwall – are being tracked by British scientists
A separate team has also circumnavigated the A76A, which is part of the A76 iceberg that came to life after the calving of the Filchner-Ronne Ice Shelf in mid-May 2021. As it traveled north, the A76 broke into three pieces, the largest of which is called A76A (pictured)
“Since glaciologists first observed the broadening of Chasm-1 in 2012, BAS science and operations teams have been anticipating calving.
WHAT IS A CALVING EVENT?
Glacier calving is a natural phenomenon caused by the forward movement of a glacier causing the tip to become unstable.
During a calving event, part of the tip of a glacier falls off, often forming an iceberg.
Glacier calving is often accompanied by a loud cracking or booming sound before blocks of ice as high as 60 meters break loose and plunge into the water.
The intrusion of this ice into the water can cause large and dangerous waves.
“High-precision GPS instruments and satellite data have been used to track the widening of the canyon, and in 2016 BAS took the precaution of moving the Halley Research Station inland to protect it.”
A separate team has also circumnavigated the A76A, which is part of the A76 iceberg that began life in mid-May 2021 following the calving of the Filchner-Ronne Ice Shelf.
As it traveled north, the A76 broke into three pieces, the largest of which is called A76A and is shaped somewhat like a giant ironing board.
At 135km long and 25km wide, it is the largest floating iceberg in the world – the size of the English county of Cornwall – and straddles the divide between the British Overseas Territories of the Falklands and South America. Georgia.
It is feared it could head east towards South Georgia and become trapped in the shallow waters of the continental shelf, or possibly to the nearby islets known as Shag Rocks.
In both areas, it can cause problems for local wildlife and people.
If the iceberg lands on the shallow seafloor in the region, it could destroy the seafloor fauna and disrupt the sea currents and foraging routes of the local wildlife.
In addition to the ecological impact, icebergs in the South Georgia region can pose a major risk to local vessels.
At 135km long and 25km wide, the A76A (pictured) is the largest floating iceberg in the world – the size of the English county of Cornwall – and heads for the divide between the British Overseas Territories of the Falklands and South Africa. Georgia
Sailing by: In January, a team of BAS scientists aboard the RRS Discovery (pictured) completed a circumnavigation of the A76A
If the A76A hits the shallow seafloor in the South Georgia region, it could destroy the seafloor fauna and disrupt the ocean currents and foraging routes of the local wildlife.
Massive icebergs like these two can take decades to melt and disappear, so they’ll be a potential threat for quite some time to come.
A81 broke free when a large crack in the ice, called Chasm-1, stretched across the entire ice shelf. It is now hovering about 150 km away from where it started, after spinning and heading south.
HOW DO SCIENTISTS MONITOR THE BRUNT ICE SHELF?
Scientists are using a network of 16 GPS instruments to measure any deformation of the Brunt Ice Shelf causing cracks, reporting hourly updates.
These include the European Space Agency’s Sentinel 2 satellites, NASA Worldview satellites, US Landsat 8 and TerraSAR-X.
They also use on-site drone imagery, as well as ground-penetrating radar to image the subsurface
The data has provided scientists with a number of ways to measure cracks with high precision.
They also used computer models and bathymetric maps to predict how close the ice shelf was to calving.
The Brunt Ice Shelf is one of the most closely monitored ice shelves in the world, being home to the Halley Research Station.
Currently, British scientists say the research station and the area around it are largely unaffected by the calving.
A81 is the region’s second major iceberg in two years. It is expected to follow in the footsteps of previous icebergs swept westward by the strong Antarctic coastal current.
In January, a team of BAS scientists aboard the RRS Discovery completed a journey around the A76A.
While there, they sampled the waters around the iceberg to better understand the potential environmental impacts.
Professor Geraint Tarling, head of the Ecosystems team at BAS, was on board RRS Discovery.
“An iceberg of this size will have a major impact on the ocean ecosystems that support the rich diversity of marine life in this Antarctic region,” he said.
These effects can be both positive and negative. On the positive side, when the iceberg melts, many nutrients are released that can support the growth of microscopic plants such as phytoplankton at the base of the oceanic food webs.’
Professor Tarling added: ‘The negative side is that this same melting, on such a large scale, dumps a lot of fresh water into the ocean, reducing salinity and making the water unsuitable for a lot of phytoplankton and the zooplankton that feed on it.
‘These effects can then enter the food web in fish, birds, seals and whales.
“Furthermore, if the A76A continues towards Shag Rocks, the erosion of the shallow seabed found there could be catastrophic for biodiverse seabed communities, including nurseries for valuable fish stocks.”
It is feared that the A76A could head east towards South Georgia and become trapped in the shallow waters of the continental shelf, or possibly head for the nearby islets known as Shag Rocks.
Antarctica’s ice sheets contain 70% of the world’s fresh water – and sea levels would rise by 55 meters if it melted
Antarctica contains an enormous amount of water.
The three ice sheets that cover the continent hold about 70 percent of our planet’s fresh water — all before warming air and oceans.
If all ice caps melted as a result of global warming, global sea levels in Antarctica would rise by at least 56 metres.
Given their magnitude, even small losses in the ice sheets can have global consequences.
In addition to rising sea levels, meltwater would slow down the world’s ocean circulation, while changing wind belts could affect the climate in the southern hemisphere.
In February 2018, NASA revealed that El Niño events cause the Antarctic ice shelf to melt by up to 10 inches each year.
El Niño and La Niña are separate events that change the water temperature of the Pacific Ocean.
The ocean fluctuates periodically between warmer than average during El Niños and cooler than average during La Niñas.
Using NASA satellite imagery, researchers found that the oceanic phenomena are causing the Antarctic ice shelves to melt while also increasing snowfall.
In March 2018, it was revealed that there is more of a giant glacier the size of France in Antarctica floating on the ocean than previously thought.
This has raised fears that it could melt faster as the climate warms and have a dramatic impact on rising sea levels.