The research, published in Nature, underscores the ACC's pivotal role in climate regulation, emphasized by Gisela Winckler, a geochemist at Columbia University's Lamont-Doherty Earth Observatory. Winckler, who co-led the sediment sampling expedition, highlights the mechanistic connection between ACC flow enhancements and Antarctic ice retreat, a scenario increasingly evident under current global warming trends.
Originating approximately 34 million years ago, the ACC's formation was facilitated by Antarctica's separation from other landmasses, initiating its powerful clockwise circulation. This current, propelled by consistent westerly winds and unimpeded by land, carries vast volumes of water at speeds reaching 2.5 miles per hour. Recent observations have shown a 40% increase in Southern Ocean wind strengths over the last 40 years, contributing to the ACC's acceleration and the warming of Antarctic ice shelves from below, primarily in the continent's western regions.
The study's lead author, Frank Lamy of Germany's Alfred Wegener Institute, points out the critical consequences of a stronger ACC, including enhanced warm water flow to Antarctica's ice shelves, leading to significant ice loss. This loss not only contributes to rising sea levels but also raises concerns about the Southern Ocean's carbon sequestration capacity amidst accelerated ACC flow.
Conducted by approximately 40 scientists across twelve countries, the study involved challenging expeditions aboard the drill ship JOIDES Resolution. Amid the harsh conditions of the austral winter, researchers extracted sediment cores from the ocean floor beneath the ACC, analyzing particle sizes to infer changes in the current's velocity over millions of years. Their findings reveal dramatic fluctuations in ACC speed corresponding with global temperature variations, further supported by correlations with West Antarctic Ice Sheet retreats during warm periods.
This research offers crucial geological evidence supporting the projection that ACC flow will continue to increase with global warming, perpetuating a trend observed in recent instrumental records. Such an increase, with its potential adverse effects, underscores the importance of understanding and addressing the interconnected dynamics of ocean currents, climate change, and ice melt.
Research Report:Five million years of Antarctic Circumpolar Current strength variability
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