Enormous A68a iceberg that was once three and a half times bigger than London released 152 BILLION tonnes of fresh water into the ocean when it scraped past South Georgia last year, study reveals
- Researchers tracked the iceberg using five different satellites in Earth orbit
- They were able to help them see when it began to melt and where it melted
- The team discovered it melted, depositing 152 billion tonnes of fresh water
- This happened close to South Georgia, found in the southern Atlantic Ocean
An enormous iceberg, that was once three and a half times larger than London, released an incredible 152 billion tonnes of fresh water into the ocean, study shows.
The massive slab of ice released the fresh water when it scraped past the island of South Georgia last year, according to researchers from the University of Leeds.
Experts have been using satellite images to track the ‘mega iceberg’, known as A68A, since it snapped off from the Larsen-C Ice Shelf in Antarctica in July 2017.
The 152 billion tonnes of fresh water dumped into the ocean from it melting is enough to fill Loch Ness 20 times over, or 61 million Olympic sized swimming pools.
It melted over three months in 2020 and 2021, according to the researchers, who say this started as it entered the seas around the sub-Antarctic island of South Georgia.
An enormous iceberg, that was once three and a half times larger than London, released an incredible 152 billion tonnes of fresh water into the ocean, study shows
HOW TO TRACK AN ICEBERG USING SATELLITES
The journey of the massive A68A iceberg started in July 2017 when it broke off from the Larsen-C Ice Shelf.
Its journey, as it moved north from the Antarctica Peninsula was charted using five different satellites.
The iceberg’s area change, as it melted on its journey to South Georgia, was recorded using a combination of Sentinel-1, Sentinel-3, and MODIS.
Meanwhile, the iceberg’s thickness change was measured using CryoSat-2 and ICESat-2 altimetry.
By combining these measurements, the iceberg’s area, thickness, and volume change were determined.
Which also allowed the team to calculate when it lost most of its structure, where it melted and the likely impact of that melting.
The iceberg began a three and a half year epic adventure in July 2017, when it broke off from the Antarctic Peninsula, taking it almost 2,500 miles across the Southern Ocean, covering an area a quarter the size of Wales.
When it first broke off rom the ice shelf it was the largest iceberg on Earth and the sixth largest on record.
It hit the headlines around the world over Christmas 2020 after coming worryingly close to South Georgia, raising concerns it could damage the fragile ecosystem.
Researchers from the Centre for Polar Observation and Modelling (CPOM) and British Antarctic Survey (BAS) used satellite measurements to chart the A68A iceberg’s area and thickness change throughout its life cycle.
The authors found that it had melted enough as it drifted to avoid damaging the sea floor around South Georgia.
However, a side effect of the melting is the colossal volume of fresh water dumped into the ocean close to the island.
This was described as a disturbance that could have a ‘profound impact on the marine habitat’ around South Georgia, by the British research team.
For the first two years of its life, A68A remained close to Antarctica in the cold waters of the Weddell Sea and experienced little in the way of melting.
However, once it began its northwards journey across Drake Passage it travelled through increasingly warm waters and began to melt.
Altogether, the iceberg thinned by 219ft, from its initial thickness of 67 metres from its initial 770ft thickness – with the rate of melting rising sharply over time.
Laura Gerrish, GIS and mapping specialist at BAS and co-author of the study said it was a fascinating iceberg to track, from creation to end of life.
‘Frequent measurements allowed us to follow every move and break-up of the berg as it moved slowly northwards through iceberg alley and into the Scotia Sea where it then gained speed and approached the island of South Georgia very closely.’
If an iceberg’s keel is too deep it can get stuck on the sea floor, the team explained, which can be disruptive in a number of different ways.
Scour marks can destroy fauna, and the iceberg itself can block ocean currents and predator foraging routes.
The iceberg began a three and a half year epic adventure in July 2017, when it broke off from the Antarctic Peninsula, taking it almost 2,500 miles across the Southern Ocean, covering an area a quarter the size of Wales
THE TOP FIVE LARGEST ICEBERGS EVER
B15: 4,200 square miles (2000)
A38: 2,664 square miles (1998)
B15A: 2,471 square miles (2002)
A68: 2,239 square miles (2017)
C19: 2,123 square miles (2002)
All the top five calved from Antarctica.
All of these potential outcomes were feared when A68A approached South Georgia, but the new study has shown that it only briefly collided with the sea floor.
It broke apart shortly after that and by the time it reached shallow waters around South Georgia, the keel had reduced to 462ft below the surface, which was just enough to avoid the seabed, which is about 492ft deep.
The ecosystem and wildlife around South Georgia will have felt the impact of the colossal iceberg’s visit, the team warned.
When icebergs detach from ice shelves, they drift with the ocean currents and wind while releasing cold fresh meltwater and nutrients as they melt.
This process influences the local ocean circulation and fosters biological production around the iceberg.
At its peak, the iceberg was melting at a rate of 22ft per month, and in total it released a staggering 152 billion tonnes of fresh water and nutrients.
Researchers from the Centre for Polar Observation and Modelling (CPOM) and British Antarctic Survey (BAS) used satellite measurements to chart the A68A iceberg’s area and thickness change throughout its life cycle
Anne Braakmann-Folgmann, lead author of the study, said: ‘This is a huge amount of melt water, and the next thing we want to learn is whether it had a positive or negative impact on the ecosystem around South Georgia.
‘Because A68A took a common route across the Drake Passage, we hope to learn more about icebergs taking a similar trajectory, and how they influence the polar oceans’.
Tommaso Parrinello, CryoSat Mission Manager at the European Space Agency, said being able to track every move of the iceberg was possible thanks to advences in satellite techniques and technology.
‘Imaging satellites record the location and shape of the iceberg and data from altimetry missions add a third dimension as they measure the height of surfaces underneath the satellites and can therefore observe how an iceberg melts.’
The findings have been published in the journal Remote Sensing of Environment.
WHAT IS THE A-68 ICEBERG AND WHAT CAUSED IT TO BREAK AWAY FROM ANTARCTICA?
In July 2017, a huge crack in Antarctica’s Larsen C ice shelf caused a trillion ton iceberg – the third biggest ever recorded – to break off from the icy southern continent.
The huge chunk of ice, dubbed iceberg A-68, measures 5,800 square kilometres (2,240 square miles), making it around the size of Delaware, or four times the area covered by Greater London.
Since A-68 broke away, it has remained unclear what will happen to the giant mass, with fears it could break up into pieces too small to track on satellite, and drift into shipping lanes.
In July 2017, a huge crack in Antarctica’s Larsen C ice shelf caused a trillion ton iceberg – the third biggest ever recorded – to break off from the icy southern continent. These detailed images were captured by instruments aboard Nasa’s Landsat 8 satellite
Experts have found that cracks are still growing on Larsen C, and if they continue to grow, it’s possible that the ice shelf could collapse.
If all of Larsen C collapses, the ice it holds back might add another 4 inches (10 cm) to global sea levels over the years.
Many scientists argue that a calving event was not necessarily due to climate change.
Instead, it may simply reflect the natural growth and decay cycle of an ice shelf.
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