UPSIDE-DOWN ‘rivers’ are melting ice shelves in Antarctica from beneath, according to a new study.
Concerned scientists have observed in greater detail how warm water rising up from the oceans is destabilising ice shelves at their weakest points.
These ‘upside-down rivers’ are known as basal channels and scientists have known about them for a number of years but never really understood them.
This new study has investigated them further and suggests they should be taken into account when modelling sea-level rise.
Glaciologist Karen Alley from the College of Wooster in Ohio said: “Warm water circulation is attacking the undersides of these ice shelves at their most vulnerable points.
“These effects matter. But exactly how much, we don’t yet know. We need to.”
Ice shelves are so crucial because they are floating extensions of land ice that stop glaciers from crashing into the sea.
About three quarters of Antarctica is surrounded by floating ice shelves.
The upside down ‘river’ effect was previously observed by a team led by Alley in 2016.
They explained at the time: “Our observations show that basal channels are associated with the development of new zones of crevassing, suggesting that these channels may cause ice fracture.
“We conclude that basal channels can form and grow quickly as a result of warm ocean water intrusion, and that they can structurally weaken ice shelves, potentially leading to rapid ice shelf loss in some areas.”
In the recent study, the researchers observed how warm water from the ocean rose above cooler water in a stream and had a negative impact on naturally weaker areas of ice shelves.
This melting was observed carving channels into the underside of the ice shelves and causing them to break off at similar points repeatedly.
Glaciologist Ted Scambos from the University of Colorado Boulder said: “We’re seeing a new process, where warm water cuts into the shelf from below.
“Like scoring a plate of glass, the trough renders the shelf weak, and in a few decades, it’s gone, freeing the ice sheet to ride out faster into the ocean.”
The researchers don’t know how much damage these underground warm currents are causing but think it’s crucial that they are studied further.
They explain in the paper: “Critically, in our modern warming climate, warming of sub-ice shelf water may already be causing basal channel deepening in shear margins, which could strongly affect buttressing and may lead to enhanced calving and ice mass loss.”
This research has been published in Science Advances.
Climate change explained
Here are the basic facts...
- Scientists have lots of evidence to show that the Earth’s climate is rapidly changing due to human activity
- Climate change will result in problems like global warming, greater risk of flooding, droughts and regular heatwaves
- Each of the last three decades have been hotter than the previous one and 17 of the 18 warmest years on record have happened during the 21st century
- The Earth only needs to increase by a few degrees for it to spell disaster
- The oceans are already warming, polar ice and glaciers are melting, sea levels are rising and we’re seeing more extreme weather events
- In 2015, almost all of the world’s nations signed a deal called the Paris Agreement which set out ways in which they could tackle climate change and try to keep temperatures below 2C
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And, experts think climate change could cause areas of the ocean to turn a “deep green” colour by 2100.
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