The Accelerating Melting of the West Antarctic Ice Sheet: A Feedback Loop Discovered

The Accelerating Melting of the West Antarctic Ice Sheet: A Feedback Loop Discovered

Recent research has brought to light a feedback loop that is believed to be hastening the melting of the floating sections of the West Antarctic Ice Sheet, which in turn leads to a rise in global sea levels. This study, titled “Antarctic Slope Undercurrent and onshore heat transport driven by ice shelf melting” and published in Science Advances, has provided new insights into the processes that are causing the melting of ice shelves beneath the ocean’s surface. Understanding these mechanisms is crucial as the West Antarctic Ice Sheet has been losing mass over the years, contributing to the overall increase in global sea levels.

One of the key players in this process is the Circumpolar Deep Water (CDW), a water mass that is approximately 4°C warmer than the local freezing temperatures. This warm water is flowing underneath the ice shelves in West Antarctica, causing them to melt from below. Given that a significant portion of the West Antarctic Ice Sheet is situated below sea level, it is highly susceptible to this intrusion of warm water, which may lead to further retreat in the future. While previous observations and models have shown that eastward undercurrents are responsible for transporting this warm water to the ice shelf cavities, the exact mechanisms behind this process have remained unclear.

Professor Alberto Naveira Garabato, from the University of Southampton, one of the co-authors of the study, highlighted the presence of a positive feedback loop in this system. As the ice shelf melts at a faster rate, more freshwater is produced, resulting in a stronger undercurrent that transports even more heat towards the ice shelves. This cycle of melting and heat transport could potentially accelerate the melting of the ice shelves, thus rendering the West Antarctic Ice Sheet less stable in the future.

Researchers from the University of California Los Angeles, MIT, and the University of Southampton utilized high-resolution simulations to delve into the dynamics of the undercurrent. Dr. Alessandro Silvano, another co-author of the study, explained that these simulations unveiled the driving force behind the deep current that carries warm water towards the ice shelves. The models suggest that when the warm CDW interacts with the ice shelf, it leads to the melting of ice and the mixing of this melted water with the lighter freshwater. This mixture then ascends through the underlying layers of water, spreading out and stretching the layer of CDW vertically. This stretching initiates a swirling motion in the water, which is then propelled along the seafloor slope towards the ice shelf, delivering more warm water in the process.

Dr. Silvano emphasized the critical need to incorporate the cavities under the ice shelves in scientific models. Models that fail to account for these cavities are likely overlooking the positive feedback loop that is perpetuating the melting of the ice shelves. As more ice melts, the underwater current intensifies, transporting even larger amounts of warm water towards the ice shelf, thus exacerbating the melting process.

The discovery of this feedback loop sheds light on the complex interplay between ice shelf melting, warm water intrusion, and the acceleration of the melting of the West Antarctic Ice Sheet. By understanding these mechanisms, scientists can better predict and mitigate the effects of global sea level rise stemming from the melting of polar ice sheets.


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