Massive teardrop-shaped indentations up to 1,300 feet long scar the underbelly of Antarctica’s Dotson Ice Shelf, baffling scientists. These formations, discovered during a recent expedition, are unlike anything observed beneath Earth’s ice sheets.
An autonomous underwater vehicle (AUV) mapped vast stretches of the ice shelf’s underside, revealing a landscape that defies conventional understanding. The findings, published in Science Advances, expose an underwater world filled with inexplicable structures.
The Dotson Ice Shelf, seven times the size of New York City, floats off the coast of West Antarctica. Oceanographer Anna Wåhlin from the University of Gothenburg led a team that sent an AUV more than 10 miles beneath the ice shelf. The robot traveled over 600 miles, creating the most detailed map ever of an ice shelf’s base.
In the western region, where warm ocean currents flow outward, researchers found smooth, eroded features and strange teardrop-shaped indentations. These divots, averaging 220 feet wide and 45 feet deep, appear in clusters across the western portion of the shelf.
Wåhlin stated, “These teardrop-shaped features are completely new to science, and their formation remains a mystery.”
The teardrops all point in the same direction, with sharp ends angled about 45 degrees to the main water flow. As they progress, they fan out into rounded shapes, suggesting an unknown force shaping the ice from below.
The eastern and central regions, where currents are slower, revealed different peculiar features. Vast, flat terraces bounded by steep walls dominate these areas. The terraces, 650 to 6,500 feet wide, are separated by faces rising 1.5 to 16 feet high. These walls form swirling patterns that resist simple explanation.
In some areas, the terraces stack on top of each other, creating a layered effect indicating a complex history of ice formation and erosion. Sharp, well-defined boundaries between terraces suggest a stable process leaving lasting imprints on the ice.
The team also discovered massive fractures running through the ice shelf. These aren’t small cracks, but giant fissures stretching from top to bottom. Older fractures show significant erosion and widening.
Researchers propose several theories to explain these formations. For the teardrop-shaped indentations, they suggest the Ekman spiral might play a role. This phenomenon involves complex interactions between water currents and Earth’s rotation, causing fluids to move in unexpected ways.
The theory suggests warm water flowing along the ice shelf’s base encounters small disturbances, perhaps cracks or debris. These disturbances create plumes of warmer water that spread asymmetrically due to the Ekman effect. The result: teardrop-shaped areas of increased melting that grow more parallel to the main current as they extend.
Terraced formations in the eastern and central regions might result from periodic intrusions of warmer surface water near the ice front. These intrusions could create distinct melting layers, forming the observed flat terraces and steep walls.
The fractures pose additional questions. While ice shelves commonly develop cracks, the extent of erosion and widening in some fractures suggests active warm water circulation within them. This could accelerate ice shelf breakup, with potential implications for sea level rise.
These discoveries significantly impact our understanding of ice shelf stability and global sea level rise. The Dotson Ice Shelf is part of the West Antarctic Ice Sheet, which contains enough water to raise global sea levels by about 11 feet if completely melted. The complex melting and erosion patterns suggest that ice loss processes in Antarctica may be more intricate than previously thought.
Wåhlin explained, “Understanding how ice melts from beneath is crucial to comprehending the Antarctic ice cycle and how ice moves from the continent to the ocean.”
The research team plans to gather more data on these bizarre formations. They aim to conduct repeat surveys to observe how the features change over time, providing insights into ice shelf melting rates and formation evolution.
However, this research faces significant challenges. The harsh Antarctic environment makes sustained observation difficult. The team lost their AUV during a follow-up mission in January 2024, underscoring the risks involved in this exploration.
The Dotson Ice Shelf discoveries open new questions about Antarctica’s hidden landscapes. What other strange formations might lurk beneath other ice shelves? How do these bizarre features influence continental ice stability? What can they reveal about Earth’s climate history?
Wåhlin and her team continue their work, braving harsh Antarctic conditions to unlock these icy secrets. Their findings not only advance scientific understanding but also reveal the unexpected phenomena that exist in Earth’s most extreme environments.
Read the full study here: https://www.science.org/doi/10.1126/sciadv.adn9188
