Experts solve the mystery of a giant hole in Antarctic sea ice

In the world of science, there’s something especially captivating about an anomaly that defies expectations. The sudden appearance of a vast hole in the Antarctic sea ice – the Maud Rise polynya – in 2016 and 2017 was precisely that kind of mystery.

Now, a team of scientists has pieced together the intricate chain of events behind this extraordinary phenomenon.

Polynyas

The Antarctic Ocean stretches out like a vast, white expanse, a seemingly unbroken sheet of ice. However, this frozen landscape isn’t entirely uniform. Closer inspection reveals occasional cracks and gaps in the ice cover, like tears in a giant white canvas. These openings, known as polynyas, are far less common than the surrounding ice, but they are much larger than the occasional crack. They are essentially sprawling stretches of unfrozen water amidst the vast sea ice.

Some polynyas form near coastlines where winds push ice from the shore. Others emerge in the open ocean, far from land. These open-ocean polynyas are much rarer and pose a bigger scientific mystery. Unlike their coastal counterparts, their formation isn’t readily explained by simple wind patterns. Instead, they seem to be triggered by a complex interplay of factors beneath the ocean’s surface.

These open water areas act like temporary windows, allowing for a significant exchange of heat and carbon dioxide to occur. Cold, deep ocean water interacts with the atmosphere at the surface, releasing heat and potentially influencing the amount of carbon dioxide the ocean absorbs. This exchange creates hotspots of activity within the icy landscape, potentially impacting regional climate patterns in the area.

Maud rise polynya: The Antarctic sea ice hole

In the frigid expanse of the Antarctic Ocean, a peculiar phenomenon emerged during the winters of 2016 and 2017. A massive hole, named the Maud Rise polynya after the submerged mountain beneath it, appeared in the sea ice.

This anomaly was particularly baffling due to its sheer scale – encompassing an area more than double the size of Wales. Furthermore, unlike most polynyas that come and go seasonally, the Maud Rise polynya persisted for multiple winters, leaving scientists thoroughly perplexed.

A new study has shed light on this icy enigma, meticulously reconstructing the sequence of events that culminated in the formation of this massive polynya. By piecing together the puzzle, researchers hope to gain a deeper understanding of the factors influencing this rare phenomenon.

Oceanic forces and Antarctic sea ice hole

The story of the Maud Rise polynya begins with an oceanic change far below the icy surface. An intensification in the Weddell Sea’s large-scale ocean circulation system – imagine a powerful underwater whirlpool – had a significant impact.

This swirling intensification caused a layer of warmer and saltier water to rise from the depths. This upwelling of warm, salty water created conditions that could potentially alter the balance between freezing and melting at the surface.

Maud Rise played a critical role. Turbulent currents, like underwater rapids, churned and interacted with the mountain’s slopes. This turbulence effectively transported salt from the surrounding waters towards the summit of the mountain.

The physics of wind-driven ocean currents, known as Ekman transport, became a major player in the polynya’s formation. The complex mechanics of this phenomenon result in ocean water being deflected at a right angle to the direction of the blowing wind. This deflection propelled the salt concentrated around Maud Rise towards its northern side. The influx of salt proved to be a crucial factor in creating the opening within the sea ice.

“Ekman transport was the essential missing ingredient that was necessary to increase the balance of salt and sustain the mixing of salt and heat towards the surface water,” explained Professor Alberto Naveira Garabato, a co-author of the study.

Broader implications

The story of the Antarctic ice hole Maud Rise polynya doesn’t end with the unraveling of its origins. Understanding these events is key to decoding broader changes in the Southern Ocean. Polynyas can leave lasting “footprints” on the ocean, shaping how water moves and distributes heat.

“The dense waters that form here can spread across the global ocean,” noted Professor Sarah Gille. This study serves as a reminder of the complex and far-reaching consequences of even localized phenomena in the context of our planet’s climate system.

The Maud Rise polynya reminds us that even in the most remote and desolate corners of Earth, dynamic processes are at play. Scientists’ relentless pursuit of knowledge sheds light on delicate balances within polar environments and the potential global consequences of change in these icy realms.

The study is published in the journal Science Advances.

Image Credit: NASA Earth Observatory

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