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New circulation pattern discovered beneath Antarctic ice shelves

In a study led by Cornell University, a remotely operated underwater robot has shed new light on the circulation of seawater beneath Antarctic ice shelves. 

The research reveals that crevasses, which were previously understood as mere cracks in the ice, play a significant role in influencing the stability of these ice shelves.

Icefin robot

This groundbreaking research was made possible by the innovative Icefin robot, which managed to navigate up and down a crevasse at the base of the Ross Ice Shelf. 

The expedition produced the very first 3D measurements of oceanic conditions near the coastline’s grounding zone – a critical intersection where the ice meets the mainland.

Key findings

The robotic survey has uncovered a previously unidentified circulation pattern. Specifically, a jet was found channeling water laterally through the crevasse. This was in addition to the recognized rising and sinking currents. 

Moreover, the survey highlighted varied ice formations which have been shaped over time by shifting flows and temperature changes.

Invaluable insight 

These discoveries will be invaluable in refining current models that predict the melting and freezing rates of ice shelves at grounding zones. Such zones, despite their significance in contributing to global sea-level rise, have rarely been directly observed.

“Crevasses move water along the coastline of an ice shelf to an extent previously unknown, and in a way models did not predict,” explained Peter Washam, a polar oceanographer and research scientist at Cornell. “The ocean takes advantage of these features, and you can ventilate the ice shelf cavity through them.”

Grounding zones

The Icefin vehicle is a slender robot of approximately 12 feet in length. In late 2019, the team deployed Icefin into a 1,900-foot borehole that had been drilled with hot water near the juncture of Antarctica’s largest ice shelf and the Kamb Ice Stream. 

Grounding zones like these are instrumental in maintaining the equilibrium of ice sheets. They are also the most susceptible to the influences of changing oceanic conditions.

Evolution of ice

Matthew Meister, a senior research engineer, masterfully steered Icefin into one of five crevasses identified near the borehole during the team’s third and final dive. 

The robot, equipped with cameras, sonar, thrusters, and sensors for measuring salinity, water temperature, and pressure, managed to ascend nearly 150 feet up one side of the crevasse and descend the opposite side.

The images revealed the evolution of ice patterns as the crevasse tapered. Observations ranged from scalloped indentations transitioning into vertical runnels, to greenish marine ice and even stalactites. 

Study implications 

The findings, according to Washam, emphasize the capacity of crevasses to transmit varying oceanic conditions, whether warmer or cooler, through the most fragile region of an ice shelf.

Funding for this monumental research came from Project RISE UP (Ross Ice Shelf and Europa Underwater Probe). The initiative falls under NASA’s Planetary Science and Technology from Analog Research program. 

The research is published in the journal Science Advances.

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