Underwater Robot Reveals New Details of Antarctic Ice Crevasses

Crevasses are the arteries of ice sheets, keeping colder and more temperate seawater in careful circulation, according to a robot. Yes, that’s right: an underwater, remotely controlled robot called Icefin.

Under the direction of a Cornell-led research team, Icefin has meandered through the many crevasses below Antarctica, scanning the slopes of ice and examining water conditions along the way.

Beginning its first expedition in 2019, the 12-feet-long cylindrical robot has since accumulated a wealth of data that will improve modeling of ice shelf melting and freezing rates, according to its handlers.

Many of the team’s recent findings were published in Science Advances.

Checking the water pressure, under the ice

Equipped with cameras, sonar and sensors, Icefin has measured the temperature, pressure and salinity of water flowing between several icesheets under Antarctica.

Within a crevasse in the base of the continent, known as the Ross Ice Shelf, the robot produced the first 3D measurements of ocean conditions near where the shelf meets the coastline, a critical juncture known as the grounding zone.

Here, the robot observed that water movement through crevasses drives asymmetric melting along the lower crevasse sidewalls and freezing in its upper reaches.

Below the Thwaites Eastern Ice Shelf in West Antarctica, for instance, where seawater is comparatively warmer, one Icefin expedition detailed melting rates 10 times higher along the crevasses’ sloping walls than along the shelf’s flat base, contributing to the grounding line’s rapid retreat.

This asymmetric melting causes freshwater (from the melting at depth) and saltwater (from freezing above) to meet, which then drives an overturning circulation. This vertical circulation pattern overlays a dominant throughflow jet, which funnels water parallel to the coastline.

These findings, say the Cornell team, highlight a crevasse’s potential to transport changing ocean conditions – warmer or colder – through an ice shelf’s most vulnerable region.

“If water heats up or cools off, it can move around in the back of the ice shelf quite vigorously, and crevasses are one of the means by which that happens,” said Peter Washam, a polar oceanographer and research scientist in Cornell University’s Department of Astronomy. “The ocean takes advantage of these features, and you can ventilate the ice shelf cavity through them.”

Washam says findings like this will improve data models of ice shelf melting and freezing rates at grounding zones – where few direct observations exist – and help understand their potential contribution to global sea-level rise.

“Crevasses move water along the coastline of an ice shelf to an extent previously unknown, and in a way models did not predict,” said Washam. “When it comes to projecting sea-level rise, that’s important to have in the models.”

Ice discharge from Antarctica contributed around 1.4 centimeters to the global mean sea level rise recorded between 1979 and 2017.

The Icefin research project was funded by Project RISE UP (Ross Ice Shelf and Europa Underwater Probe), part of NASA’s Planetary Science and Technology from Analog Research program.

Reference: Washam P, Lawrence JD, Stevens CL, et al. Direct observations of melting, freezing, and ocean circulation in an ice shelf basal crevasse. Sci. Adv. 2023;(9):7638. doi: 10.1126/sciadv.adi7638

This article is a rework of a press release issued by the Cornell Chronicle. Material has been edited for length and content.