A new study published in Environmental Research Letters reveals that the melting of Antarctic ice is causing the world's strongest ocean current, the Antarctic Circumpolar Current (ACC), to slow down, posing risks to global climate patterns and marine ecosystems. Researchers from the University of Melbourne and NORCE Norway Research Centre conducted high-resolution simulations to analyze the impact of changing temperature, salinity, and wind conditions on ocean currents and heat transport, according to Science Daily.
The ACC plays a crucial role in global climate regulation as the main mechanism for exchanging heat, carbon dioxide, nutrients, chemicals, and biology across ocean basins. The current moves clockwise around Antarctica, transporting about 140 billion liters of water per second, and acts as a barrier isolating Antarctica's ecosystems from the rest of the world.
The study warns that under a high carbon emissions scenario, the ACC could slow by about 20% by 2050, with implications for marine ecosystems and climate. Researchers noted that melting ice shelves are a major factor in the slowdown of the ACC.
"The melting ice sheets dump vast quantities of fresh water into the salty ocean. This sudden change in ocean salinity has a series of consequences—including the weakening of the sinking of surface ocean water to the deep, and, based on this study, a weakening of the strong ocean jet that surrounds Antarctica," said Associate Professor Dr. Bishakhdatta Gayen, according to El Economista.
Dr. Taimoor Sohail from the University of Melbourne emphasized that coordinated efforts to reduce carbon emissions are crucial to limit Antarctic ice melting and prevent the predicted slowdown of the Antarctic Circumpolar Current. "The Paris Agreement of 2015 aimed to limit global warming to 1.5 degrees Celsius above pre-industrial levels. Many scientists agree that we have already reached this 1.5-degree target, and temperatures are likely to increase, with indirect impacts on Antarctic ice melting," Sohail said.
The ACC acts like a moat around Antarctica, helping to keep warm water at bay and protecting vulnerable ice sheets. If emissions increase over the next 25 years, the current may slow down, causing more warm water to reach the Antarctic coasts and further accelerating ice melting. This could lead to accelerated sea level rise and ocean warming, threatening coastal areas, including the eastern United States.
Researchers used one of the strongest supercomputers in Australia, GADI, to model how the melting of ice sheets affects the ACC and its response to meltwater from Antarctic ice shelves. The underlying model, ACCESS-OM2-01, developed by Australian researchers over several years, captures features often missed by other models, such as eddies, making it more accurate in assessing changes in the ACC's strength and behavior due to global warming.
As the ACC slows, the influx of fresh water is causing changes in the ocean's density (salinity) and flow patterns, which is expected to alter ocean circulation and affect the balance of ocean currents. "The ocean is extremely complex and delicately balanced. If this 'engine' of currents malfunctions, serious consequences could occur including more climate variability, certain regions becoming extreme, and accelerated global warming due to the ocean's reduced ability to store carbon," said Gayen, according to Economic Times.
As the ACC slows, it could disrupt nutrient circulation and further climate changes worldwide, impacting marine ecosystems and species migration patterns. The arrival of invasive species could disrupt the food web in Antarctica, potentially changing the available diet of Antarctic penguins. The ACC serves as a crucial barrier that isolates Antarctica's ecosystems, preventing invasive species such as southern bull kelp, shrimp, and mollusks from reaching the continent.
Despite the bleak prognosis, researchers believe that with proactive and coordinated international actions, there is a chance to address and potentially avert the effects of climate change on the oceans. "Concerted efforts to reduce greenhouse gas emissions could still limit melting around Antarctica," said Gayen, according to Australian Geographic.
The article was written with the assistance of a news analysis system.