April 24, 2024

The world’s strongest ocean current is accelerating and causing problems • Earth.com

The Antarctic Circumpolar Current (ACC) is the most powerful current on Earth, encircling Antarctica and influencing global climate.

In recent decades, observations show that it has been accelerating. Experts were unsure whether this was the result of human-caused warming or a natural pattern.

However, scientists have discovered that this oceanic powerhouse is getting even stronger. What does this mean for the future of our planet?

Ocean depths

An international team of researchers embarked on a daring expedition into remote, turbulent waters. The goal was to recover sediment cores containing million-year-old clues about the behavior of the ACC along with Earth’s temperature changes.

Through meticulous analysis, experts discovered the secrets stored in the sediment layers.

Current, weather and ice

The study reveals a strong link between the speed of the ACC and the Earth’s overall temperature, just like a thermostat.

During colder periods, the current decreased. But when the planet warmed naturally in the past, the current responded by accelerating.

What is truly alarming is that these previous ACC accelerations were directly linked to major ice losses from Antarctica. We are seeing a similar acceleration of ACC right nowdriven by human-caused warming.

This suggests that Antarctic ice will likely continue to retreat – potentially fueling sea level rise and even affecting the ocean’s ability to absorb carbon from our atmosphere.

Why Antarctic currents are important

“This is the most powerful and fastest current on the planet. It is arguably the most important current in Earth’s climate system,” said Gisela Winckler, a geochemist at Columbia University’s Lamont-Doherty Earth Observatory.

ACC is a major player in Earth’s climate system, acting as a global conveyor belt that redistributes heat and nutrients throughout the world’s oceans.

Features of ACC

Vast scale: The ACC is the largest ocean current, stretching around Antarctica and connecting the Atlantic, Pacific and Indian oceans. It is the only ocean current that completely encircles the globe, free from any continental barriers.

Volume and speed: Carries more water than any other stream — approximately 135 million cubic meters per second. Its flow is influenced by wind patterns, the 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 spans widths of up to 2,000 kilometers (about 1,243 miles).

ACC functions

Climate regulation: ACC plays a crucial role in regulating global climate. It helps distribute heat around the planet by moving hot water from the equator toward the poles and cold water toward the equator.

Carbon sequestration: ACC is fundamental to the global carbon cycle. It absorbs significant 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 stirring water from different depths (upwelling), ACC brings nutrients from the depths to the surface, supporting marine ecosystems around Antarctica and beyond.

Importance of ACC

Support for biodiversity: Nutrients brought to the surface by ACC support phytoplankton blooms, which are the foundation of the Antarctic food chain, supporting a diverse range 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 Earth’s climate system.

Climate change indicator: Changes in the speed or pattern of the ACC may indicate changes in the global climate system. Its acceleration due to increasing westerly winds is a concern as it could have implications for sea level rise and global temperature patterns.

The influence of the ocean on the Antarctic current

How does ACC acceleration directly affect things? See how:

Melting of Antarctic ice shelves

Winds over the Southern Ocean have become about 40% stronger in recent decades, boosting the ACC and pulling warmer waters toward Antarctica’s floating ice shelves.

These platforms work like giant plugs that trap huge glaciers. Hotter water corrodes them from below, causing them to melt.

“If you leave an ice cube in the air, it takes a while to melt. If you put it in contact with warm water, it goes away quickly”, explains Winckler.

Uncertain carbon sponge

The oceans around Antarctica are a vital component of Earth’s carbon cycle. They absorb a substantial amount of carbon dioxide (CO2) that humans emit into the atmosphere, around 40%, acting as a “carbon sponge”.

This process is essential to moderate global warming, as it removes CO2 from the atmosphere, where it would otherwise retain heat, contributing to the greenhouse effect.

Future of the Antarctic current

“These findings provide geological evidence supporting further increase in ACC flux with continued global warming,” the researchers noted.

As humans continue to pump greenhouse gases into the atmosphere, the ACC will almost certainly continue to accelerate. This is likely to trigger more intense warming around Antarctica, further destabilizing the West Antarctic Ice Sheet.

This vast reservoir of ice, much of it below sea level, has the potential to dramatically raise global sea levels.

It’s time to pay attention to the Antarctic current

The ACC isn’t getting as much attention as rising temperatures or melting Arctic ice caps, but perhaps it should. This powerful current has a complex relationship with our planet’s climate system, and changes in it will have cascading effects across the world.

Understanding these complex forces, along with reducing greenhouse gas emissions, is essential to prepare for a future where accelerated ACC, rising seas and extreme weather could reshape our world.

The study is published in the journal Nature.


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