An ancient gorge in the rocks below East and West Antarctica controls the flow of water under the Ross Ice Shelf and the speed at which parts of the ice melt.
The boundary was discovered with the help of a new, flat-mounted detector that can collect magnetic and gravitational data on the ice shelf as it flies around.
In addition, the researchers also discovered that a piece of open water in the Ross Sea that cools the ocean in the winter can also lead to significant warming and local ice melt in the summer.
Together, the findings point to the importance of local sea currents in the future retreat of the Antarctic ice shelf.
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An ancient gorge in the rocks below East and West Antarctica controls the flow of water under the Ross Ice Shelf (pictured, stock image) and the speed at which parts of the ice melt
The Ross Ice Shelf is a huge expanse of floating ice that delays the release of about 20 percent of the grounded Antarctic ice in the ocean, making insight into its evolution essential for predicting future sea level rise.
To better determine how the Ross Ice Shelf interacts with the ocean, atmosphere and underlying geology, an international team led by researchers from Columbia University has begun to perform a comprehensive overview of the shelf.
This is no mean feat, since the Ross Ice Shelf is as large as Spain, and contains many areas in which the ice is more than a thousand feet thick, thus preventing traditional ship-based surveys of the seabed.
Their solution was to develop IcePod, a unique cargo-ship mounted system specially designed to collect high-resolution data from the polar regions.
IcePod can measure the height, thickness and internal structure of the ice shelf, as well as the magnetic and gravity-based signals from the underlying rock.
As they flew back and forth across the ice shelf, researchers discovered that the IcePod magnetometer – which measures the strength of the Earth's magnetic field – continued to record unusual signals as they crossed the center of the shelf.
These magnetic anomalies, the researchers concluded, reflected a transition over a previously undiscovered segment of the geological boundary between the rocks of East and West Antarctica.
On the west side lie young sedimentary rocks, volcanic materials and vast continental blocks, while the east side is characterized by old continental material and the remains of former mountain ranges.
The team then modeled the shape of the seabed under the ice shelf using measurements from the Earth's gravitational field.
& # 39; We could see that the seabed on the East Antarctic side was much deeper than the West, & # 39; said lead researcher Kirsty Tinto, a polar geophysicist at the Lamont-Doherty Earth Observatory at Columbia University.
& # 39; That affects the way ocean water circulates under the ice shelf, & # 39; she added.
To find out how, the researchers used their newly created map of the seabird to model the circulatory system under the Ross Ice Shelf and determine its effect on the shelf itself.
Water that flows under the ice shelf is first cooled in the Ross Sea (photo) by the cold winter atmosphere as it passes through an open water area known as the Ross Shelf Polynya
They found that little hot water arrives compared to the Amundsen Sea in the east, where warm currents cross the shallow water, resulting in the melting of the above ice plates.
Instead, all the water flowing under the ice shelf from the warmer deep ocean is first cooled in the Ross Sea by the cold winter atmosphere as it flows through an open water area known as the Ross Shelf Polynya.
This cold water can melt deeper parts of the eastern Antarctic glaciers, the researchers revealed, but such currents are being driven away from the western South Pole side by the change in depth encountered on the old tectonic border.
However, the team was surprised to see that the polynya in the summer can also lead to the intense melting of the leading edge of the ice plate, with the open strip of water allowing the upper ocean to warm up.
They confirmed these findings by looking at the internal structure of the ice plate as seen by radar images.
Experts found that little hot water reaches the Ross Ice Shelf compared to the Amundsen Sea in the east, where warm currents cross the shallow water, resulting in the melting of the upper ice plateaus.
& # 39; We discovered that the ice loss from the Ross Ice Shelf and the flow of the adjacent, grounded ice are sensitive to changes in processes along the ice front & # 39 ;, said co-author and polarographer. Laurie Padman of the Seattle-based institute for Earth and Space Research.
Such changes, he added, may include: & # 39; increased summer warming as the sea ice or clouds decrease & # 39 ;.
Together, the findings indicate how important it is to consider local currents near the ice in models used to predict future Antarctic ice loss, rather than just large-scale changes in the circulation of warm, deep water.
& # 39; We discovered that it is these local processes that we need to understand to make good predictions & # 39 ;, said Dr. Tinto.
The full findings of the study were published in the journal Nature Geoscience.
HOW CAN A HEATING ANTARCTICA IMPACT SEA LEVELS?
Antarctica has an enormous amount of water.
The three ice sheets that cover the continent contain about 70 percent of our planet's fresh water – and these are all for heating air and oceans.
If all ice sheets melted due to global warming, Antarctica would raise sea levels on Earth by at least 183ft (56m).
Given their size, even small losses in the ice sheets can have global consequences.
In addition to rising sea levels, melt water would slow ocean circulation in the world, while changing seat belts can affect the climate in the southern hemisphere.
In February 2018, NASA unveiled El Niño events that melt the ice sheet in Antarctica to 25 centimeters 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 images, researchers discovered that oceanic phenomena cause Antarctic ice sheets to melt and snowfall to increase.
It was revealed in March 2018 that more of a giant French glacier in Antarctica is floating on the ocean than previously thought.
This has increased the fear that it could melt faster if the climate gets warmer and has a dramatic impact on rising sea levels.
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