In Antarctica, a unique phenomenon has caught the attention of NASA scientists. A massive black patch, unlike the typical bright winter sea ice over the Southern Ocean, left satellite operators perplexed. This unprecedented occurrence, known as a polynya, expanded to the size of Switzerland and remained open for weeks above a submerged plateau called Maud Rise. This mysterious event, hundreds of miles from the nearest shoreline, led researchers to question how such a vast opening in the ice could emerge.
The Southern Ocean, normally stratified like a layer cake, experienced a disruption when the polynya formed. In order for a polynya to develop, the surface water must become saltier and heavier than the layers beneath it, causing the stack to flip. Once this happens, convection occurs, resulting in the fracture of the ice lid and heat escaping upward, allowing the ocean to release gases. While coastal polynyas are common due to strong winds pushing ice away from land, occurrences like the one above Maud Rise are much rarer.
The Maud Rise polynya, which appeared in the winters of 2017, resembled a phenomenon observed in the 1970s. During that time, the clockwise Weddell Gyre expedited, drawing warmer, saltier water toward the surface and softening the ice from below. However, the mystery of polynyas persisted as the surface water should have freshened and halted mixing, but another input of salt was at play. Roaring storms and atmospheric rivers added warmth and saline water to the mix, creating the perfect conditions for a polynya above Maud Rise.
The crucial missing ingredient in understanding polynyas, known as Ekman transport, was also identified in the research. This process involves wind pushing salt-laden water onto specific areas, where convection can intensify. The unexpected opening above Maud Rise released excess heat into the atmosphere, impacting the global climate system. The study conducted by a team of researchers highlighted the long-lasting effects of polynyas on ocean currents and heat distribution worldwide.
As the planet warms and shifts, the future frequency of polynyas like the one above Maud Rise remains uncertain. The negative trend in Southern Ocean sea ice since 2016 suggests a changing climate pattern that could potentially alter the dynamics of polynyas. The implications of these phenomena go beyond Antarctica, shaping global ocean currents and climate regulation. Scientists anticipate further research and observation in the coming years to understand the full extent of polynyas’ influence on the Earth’s climate system.