Melting ice shelves in Antarctica have poured 66.9 trillion tonnes of fresh water into the oceans over the last 25 years, scientists claim.
Over the same time period, 43.8 percent of Antarctica’s ice shelves have reduced in volume.
Leeds University scientists calculated almost 67 trillion tonnes of ice melted into the ocean, offset by 59 trillion tonnes of ice being added to the ice shelves, giving a net loss of 7.5 trillion tonnes.
The team says that ice shelves on the western side of Antarctica were most impacted
with human-induced global warming the likely cause.
In total, 71 of the 162 ice shelves that surround Antarctica have reduced in volume between 1997 to 2021, according to the study published in the journal Scientific Advances.
Almost all the ice shelves on the western side of Antarctica experienced ice loss whereas most of the ice shelves on the eastern side stayed the same or increased in volume.
The researchers analyzed over 100,000 satellite radar images to produce this major assessment of the “state of the health” of the ice shelves.
If the ice shelves disappear or even diminish, there will be major knock-on effects for the ice system on Antarctica and for global ocean circulation.
This is the giant “conveyor belt” which moves nutrients as well as heat and carbon from the polar ecosystem.
Dr Benjamin Davison, a research fellow at the University of Leeds who led the study, said: “There is a mixed picture of ice-shelf deterioration, and this is to do with the ocean temperature and ocean currents around Antarctica.
“The western half is exposed to warm water, which can rapidly erode the ice shelves from below, whereas much of East Antarctica is currently protected from nearby warm water by a band of cold water at the coast.”
The continent of Antarctica is 50 times the size of the UK and the seas on the western side experience different currents and winds than on the east.
This is driving warmer water underneath the ice shelves on the western flank.
Dr Davison, an expert in Earth Observation of polar regions in the School of Earth and Environment, said: “We expected most ice shelves to go through cycles of rapid, but short-lived shrinking, then to regrow slowly.
“Instead, we see that almost half of them are shrinking with no sign of recovery.”
They believe that global warming is to blame because if it was due to natural variation in climate patterns, there would have been some signs of ice regrowth on the western ice shelves.
Ice shelves float on the seas surrounding Antarctica and are extensions to the ice sheet that covers much of the continent.
The ice shelves act as giant “plugs” at the end of glaciers, slowing down the flow of ice draining into the oceans.
When the ice shelves thin or reduce in size, these plugs weaken with the result that the rate of ice lost from the glaciers increases.
Some of the biggest ice losses were observed on the Getz Ice Shelf, where 1.9 trillion tonnes of ice were lost over the 25-year study period.
Just five percent of that was due to calving, where large chunks of ice breakaway from the shelf and move into the ocean.
The rest was due to melting at the base of the ice shelf.
Similarly on the Pine Island Ice Shelf, 1.3 trillion tonnes of ice were lost with around a third of that loss, 450 billion tonnes due to calving, the rest due to melting from the underside of the ice shelf.
In contrast, the Amery Ice Shelf, on the east side of Antarctica, gained 1.2 trillion tonnes of ice. It is surrounded by much colder waters.
Over the 25-year study period, the researchers estimated that 66.9 trillion tonnes of freshwater went into the Southern Ocean around Antarctica from the ice shelves alone.
In the Southern Ocean, dense salty water sinks to the ocean floor as part of the global ocean conveyor belt. This sinking of water acts as one of the engines that drive the ocean conveyor belt.
Freshwater from Antarctica dilutes the salty ocean water, making it fresher and lighter, which takes longer to sink and this can weaken the ocean circulation system
A different study, published in the journal Nature Climate Change, shows that this process may already be underway.
Professor Anna Hogg, also from the University of Leeds and a co-author of the study, said: “The study has generated important findings.
“We tend to think of ice shelves as going through cyclical advances and retreats. Instead, we are seeing a steady attrition due to melting and calving.
“Many of the ice shelves have deteriorated a lot as 48 lost more than 30 percent of their initial mass over just 25 years.
“This is further evidence that Antarctica is changing because the climate is warming.
“The study provides a baseline measure from which we can see further changes that may emerge as the climate gets warmer.”
Details captured by satellite sensors are so great scientists have been able to track year-by-year changes in Antarctica.
Produced in association with SWNS Talker
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