Antarctic Circumpolar Current Responds to Global Climate: Study

March 29, 2024

A recent study published in the journal Nature has revealed that the Antarctic Circumpolar Current (ACC), an ocean current connecting the Indian, Atlantic, and Pacific oceans, has been speeding up in recent decades due to a warming climate.

The study, which examined the ACC’s speed over the last 5.3 million years, found that the current responds to global climate changes by either accelerating or slowing down, with significant consequences for the stability of Antarctica’s ice sheets.

Importance of the Antarctic Circumpolar Current

The ACC plays a crucial role in regulating the global climate and is the world’s most powerful means of inter-basin exchange of heat, carbon dioxide, chemicals, and biology.

Powered by continuous westerly winds, the ocean current circles Antarctica clockwise at about 4 kilometers per hour, carrying between 165 million and 182 million cubic meters of water each second. The ACC extends from the ocean’s surface to its bottom and measures up to 2,000 kilometers across.

Recent Changes in the ACC

Over the past four decades, the winds over the Southern Ocean, which encircles Antarctica, have gained strength by about 40 percent. As a result, the ACC has accelerated, causing relatively warm water from higher latitudes to reach the South Pole. In some parts of Antarctica, particularly in the western region, these warm waters are melting the undersides of ice shelves, contributing to ice loss and sea-level rise.

Study Findings and Implications

The study’s lead author, Frank Lamy from Germany’s Alfred Wegener Institute, emphasized the importance of understanding how the ACC responds to climate fluctuations, as this information could help in forecasting future climate and the stability of the Antarctic ice sheet.

By analyzing core samples from the Earth’s crust in the central South Pacific, the research team reconstructed the ACC’s flow speed over millions of years using an advanced X-ray technique.

The study found that during the last 800,000 years, when atmospheric carbon dioxide (CO2) levels varied from 170 to 300 parts per million, there was a close connection between ACC strength and glacial cycles. In warm periods and when atmospheric CO2 levels rose, the flow speed increased by up to 80 percent compared to the present, while it decreased by up to 50 percent during ice ages.

Future Projections and Need for Further Research

The researchers warn that due to human-caused climate change, the ACC is likely to grow stronger in the future, potentially accelerating the melting of Antarctic ice.

However, Lamy noted that more analysis is needed, as there might be significant differences in other sectors of the ACC, such as the Indian and Atlantic sectors. He emphasized the need for more sediment records from the vast ACC to better understand its spatial heterogeneity.

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