Underwater robot survives voyage to ‘never-accessed region of the planet’

Using an underwater survey robot, oceanographers are obtaining the first measurements ever collected beneath the vast ice shelves of East Antarctica. But for a moment, it wasn’t clear when (or if) the bright yellow float would return to the ocean surface after diving beneath the ice.

“We were lucky,” Steve Rintoul, an oceanographer at the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO), said in a statement.

Part of the ongoing Argo survey project, the autonomous device spent more than two and a half years drifting through approximately 186 miles of frigid ocean currents. During that time, the device collected nearly 200 reports containing data on water temperature, pressure and salinity, as well as oxygen, pH and nitrate levels. However, the float at one point traveled beneath the Denman and Shackleton ice shelves, where it spent the next eight months collecting data from a never-before-accessible region of the planet.

“These unprecedented observations provide new insights into the vulnerability of ice shelves,” added Rintoul.

The team’s findings, detailed in a study published in the journal Scientific advancesstrengthen and update our current understanding of ice shelf health. The Shackleton Ice Shelf is the northernmost in East Antarctica and remains unexposed to warmer waters that could melt it from below. However, Denman Glacier is in a more precarious state. Denman’s disappearance alone would contribute to a nearly five-foot rise in global sea levels. Unfortunately, Denman is now exposed to warmer waters, which could accelerate melt rates and facilitate more unstable ice retreat.

This melting depends largely on the condition of the ocean within a nearly 33-foot-thick boundary layer that exists directly beneath the ice shelf itself. Argo floats are designed to measure various features within this boundary layer, but so far none have spent this much time near such a feature.

“In the face of the enormity of such a wild region, it’s an astonishing story of the little float that could do it,” added Delphine Lannuzel, an oceanographer unaffiliated with the study who sampled ocean health near the Denman Plateau earlier this year. “Under incredibly grueling conditions, a relatively small instrument provided us with a wealth of invaluable information.”

Researchers hope the Argo float won’t be the last to visit these and other ice shelves. Rintoul explained that these types of robots offer vital data that helps improve climate computer models and reduce uncertainties about sea level rise.

“Deploying more floats along the Antarctic continental shelf would transform our understanding of the vulnerability of ice shelves to ocean changes,” Rintoul said.

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