The Antarctic Circumpolar Current (ACC) is the most powerful current on Earth, surrounding Antarctica and influencing global climate.
Over the past few decades, observations show that this phenomenon has been accelerating. Experts were not sure whether this was a result of human-caused global warming or a natural pattern.
However, scientists have discovered that this oceanic force is getting stronger. What does this mean for the future of our planet?
Ocean depths
An international team of researchers has embarked on a daring expedition into remote, turbulent waters. The goal was to recover sediment cores that contain millions of years' worth of evidence about the behavior of the ACC along with changes in Earth's temperature.
Through careful analysis, experts revealed the secrets contained within the layers of sediment.
Current, climate and ice
The study reveals a strong link between the speed of the Asian astronomical center and the Earth's overall temperature, just like a thermostat.
During cold periods, the current slows down. But when the planet warmed naturally in the past, the current responded by accelerating.
What's really worrying is that previous ACC accelerations were directly linked to significant Antarctic ice losses. We observe a similar speedup for ACC nowdriven by human-caused global warming.
This suggests that Antarctica's ice is likely to continue to retreat, which could lead to sea levels rising and even impact the oceans' ability to absorb carbon from our atmosphere.
Why are Antarctic currents important?
“This is the strongest and fastest current on the planet. It is arguably the most important current in Earth’s climate system,” said Gisela Winkler, a geochemist at Columbia University. Lamont-Doherty Earth Observatory.
The ACC is a major player in Earth's climate system, acting as a global conveyor belt that redistributes heat and nutrients across the world's oceans.
Characteristics of the ACC
wide range: The ACC is the largest ocean current, extending around Antarctica and connecting the Atlantic, Pacific, and Indian Oceans. It is the only ocean current that completely surrounds the Earth and is free from any continental barriers.
Size and speed: It transports more water than any other stream – about 135 million cubic meters per second. Its flow is affected by wind patterns, Earth's rotation, and differences in water density.
Depth and width: The ACC extends from the surface to the ocean floor, reaching depths of up to 4,000 meters (about 13,123 feet) and extending up to 2,000 kilometers (about 1,243 miles) wide.
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Climate regulation: The ACC plays a crucial role in regulating global climate. It helps distribute heat around the planet by moving warm water from the equator toward the poles and cold water toward the equator.
Carbon sequestration: The ACC has an active role in the global carbon cycle. It absorbs large amounts of carbon dioxide from the atmosphere, transporting it to the depths of the ocean where it can be stored for centuries.
Nutrient distribution: By moving water from different depths (bottom water rising to the surface), ACC brings nutrients from the depths to the surface, supporting marine ecosystems around Antarctica and beyond.
The importance of the ACC
Support biodiversity: The nutrients brought to the surface by the ACC support the proliferation of phytoplankton, which forms the basis of the Antarctic food web, and sustains a variety of marine life from krill to whales.
Impact on global ocean circulation: The ACC influences global ocean circulation patterns, including the formation of deep-water masses in the North Atlantic that drive the global conveyor belt, a critical component of the Earth's climate system.
Climate change index: Changes in the speed or pattern of the ACC can indicate changes in the global climate system. Its acceleration due to increased westerly winds is a concern, because it may have implications for sea level rise and global temperature patterns.
The influence of the ocean on the Antarctic current
How does the ACC acceleration impact things directly? Here's how:
Melting ice shelves in Antarctica
The strength of winds over the Southern Ocean has increased by about 40% in the past few decades, pushing the Asian Ocean Center and pulling warm water towards Antarctica's floating ice shelves.
These shelves act like giant plugs holding back huge glaciers. Warm water erodes them from below, causing them to melt.
“If you leave an ice cube in the air, it will take a while to melt. If you put it in contact with warm water, it disappears quickly,” Winkler explains.
Unconfirmed carbon sponge
The oceans surrounding Antarctica are a vital component of Earth's carbon cycle. They absorb a large amount of the carbon dioxide that humans emit into the atmosphere, approximately 40%, and act as a “carbon sponge.”
This process is crucial to mitigating global warming, because it removes carbon dioxide from the atmosphere, where it may trap heat, contributing to global warming.
The future of the Antarctic current
“These results provide geological evidence supporting increased ACC flow as global warming continues,” the researchers noted.
As humans continue to pump greenhouse gases into the atmosphere, the ACC will almost certainly continue its pace. This will likely lead to higher temperatures around Antarctica, further destabilizing the West Antarctica ice sheet.
This massive reservoir of ice, much of which lies below sea level, has the potential to raise global sea levels dramatically.
It's time to pay attention to the Antarctic Current
The ACC doesn't get as much attention as rising temperatures or melting Arctic ice caps, but maybe it should. This great current has a complex relationship with our planet's climate system, and changes to it will have ripple effects around the world.
Understanding these complex forces, along with reducing greenhouse gas emissions, is essential to prepare for a future where accelerating ACC, rising sea levels, and extreme weather could reshape our world.
The study is published in the journal nature.
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