A team of researchers has uncovered the long-elusive explanation behind a rare phenomenon: the formation of a massive opening in the sea ice around Antarctica. This unusual event, known as a polynya, occurred during the winters of 2016 and 2017, covering an area nearly twice the size of Wales. Their findings, published in Science Advances, shed light on the complex processes that drive the formation and persistence of such openings in the icy expanse of the Southern Ocean.
Led by Aditya Narayanan, a Postdoctoral Research Fellow at the University of Southampton, the study delved into the Maud Rise polynya, named after the submerged mountain-like feature in the Weddell Sea. By analyzing interactions between wind patterns, ocean currents, and the unique underwater topography, the researchers unveiled the mechanisms responsible for the emergence of this enigmatic feature.
Unlike polynyas commonly found in coastal regions, which result from strong winds pushing ice away from the shore, the Maud Rise polynya formed hundreds of kilometers from the coast, over open ocean waters. This distinction puzzled scientists for decades, as the conditions required for such a phenomenon remained elusive.
The team discovered that the Maud Rise polynya’s formation was facilitated by a combination of factors, including an intensification of the circular ocean current around the Weddell Sea. This strengthening current led to the upwelling of warm, salty water from the deep ocean layers, enhancing the mixing of salt and heat near the surface.
Fabien Roquet, a Professor in Physical Oceanography at the University of Gothenburg and co-author of the study, emphasized the role of upwelling in melting sea ice, noting its contribution to the persistence of the polynya. However, the researchers identified an additional mechanism crucial for sustaining the opening: Ekman transport.
Ekman transport, a process where water moves perpendicular to the direction of surface winds, played a pivotal role in transporting salt onto the northern flank of Maud Rise. This influx of salt, coupled with the upwelling of warm water, fueled the continuous mixing of heat and salt near the ocean’s surface, sustaining the polynya over several weeks.
The significance of polynyas extends beyond their immediate vicinity, influencing heat and carbon transfer between the ocean and atmosphere. Professor Sarah Gille from the University of California San Diego highlighted their impact on regional climate dynamics, emphasizing their role in shaping ocean currents and redistributing heat across the globe.
Moreover, the study underscores the broader implications of these findings for understanding sea ice dynamics in the Southern Ocean. Professor Gille noted a negative trend in sea ice extent since 2016, signaling a potential shift in the region’s climate regime.
As researchers continue to unravel the mysteries of Antarctic sea ice dynamics, insights gleaned from studies like this offer valuable perspectives on the interconnected processes shaping Earth’s polar regions.
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