Strange shift beneath Antarctic glacier may reflect Jupiter's icy moon

Cameras on a robot named Icefin deployed beneath the ice of the Kamb Ice Stream, where it meets the Ross Ice Shelf in western Antarctica, have revealed a sudden change in scenery, according to a study published in Nature on March 2. 

A change from 'smooth, cloudy meteoric ice walls suddenly to green and rougher in texture, transitioning to salty marine ice, was described by researchers. 

And that's not all. They believe that marine ice similar to this may be an analog for conditions on Jupiter's icy moon Europa, which NASA's Europa Clipper orbital mission will explore beginning in 2024. Significantly, the findings may inform future lander missions to one day conduct a direct search for microbial life in the ice.

"And then it just got weirder as we went higher up"

The change, according to the U.S.-New Zealand study team, is proof of "ice pumping"—a mechanism that has never before been seen directly in an ice shelf but is crucial to the stability of its structure.

"We were looking at ice that had just melted less than 100 feet below, flowed up into the crevasse, and then refrozen," said co-author Justin Lawrence in a press release. "And then it just got weirder as we went higher up."

The team saw various ice features that revealed essential details regarding water mixing and melt rates. The "weirder" formations were located near the top of the chasm and comprised globs of ice and finger-like protrusions that resembled brinicles. Structures in other ice sheet areas contained ripples, vertical runnels, and dimples resembling golf balls.

Monitoring West Antarctic ice sheets

Thwaites is one of the continent's most unstable glaciers because it is exposed to warm ocean currents. Contrastingly, since the late 1800s, the Kamb Ice Stream has been stagnant in an area with extremely cold ocean waters. 

Current ice loss from Western Antarctica is partially countered by Kamb. But, if it reactivates, the region's contribution to sea-level rise could climb by 12 percent.

"Antarctica is a complex system, and it's important to understand both ends of the spectrum – systems already undergoing rapid change as well as those quieter systems where future change poses a risk," said co-author Schmidt. "Observing Kamb and Thwaites together helps us learn more."

The study is anticipated to enhance sea-level rise predictions when coupled with the recently reported exploration by a second Icefin vehicle that revealed the rapidly moving 'Doomsday' Thwaites Glacier.

Moreso, NASA provided funding for developing Icefin and the Kamb exploration to expand ocean exploration beyond the planet's oceans.

The complete study was published in Nature Geoscience on March 2.

Study abstract:

Ice streams flowing into Ross Ice Shelf are presently responsible for around 10% of the mass flux from West Antarctica, with the noteworthy exception of the Kamb Ice Stream, which stagnated in the late 1800s. The subsequent reduction in ice supply led to a grounding-line retreat at the coastal margin where Kamb transitions into the floating Ross Ice Shelf. Grounding-line migration is linked to broader changes in ice-sheet mass balance and sea level, but our understanding of related ice, ocean, and seafloor interactions is limited by the difficulty in accessing these remote regions. Here we report in situ observations from an underwater vehicle deployed at Kamb that show how fine-scale variability in ice and ocean structure combine to influence a diversity of ice–ocean interactions. We found a stratified water column within a tenth of a degree of freezing at the ice base and mapped basal crevasses with super-cooled water and active marine ice formation. At the seafloor, we interpret parallel ridges as crevasse impressions left as the ice lifted off during grounding-line retreat. These observations from a recently ungrounded sub-shelf environment illuminate both the geomorphological signatures of past grounding-line retreats and the fine-scale sensitivity of ongoing ice–ocean interactions to ice topography.