New dataset suggests that East Antarctica ice shelves may be unstable

A detailed 14-year record of ocean circulation beneath a key ice shelf in Antarctica reveals that ice shelves in East Antarctica may be less stable than previously assumed.

 Fimbulisen Ice Shelf is of critical importance globally because it helps to buttress a vast section of the East Antarctic Ice Sheet which might otherwise rapidly slide into the sea and exacerbate global sea level rise.

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Water sneaking beneath the ice

The study uncovered a complex interplay between different water masses beneath the Fimbulisen Ice Shelf.

Warm deep water, a key driver of melting, occasionally intrudes deep into the cavity under the ice shelf.

At shallower depths, a layer of solar-heated surface water mixes with colder water beneath the ice shelf in late summer and autumn. Surprisingly, this buoyant water can separate colder ice shelf water from the ice base, altering seasonal melting dynamics.

This variability indicates a finely balanced system, where changes in ocean and atmospheric conditions could have large implications for ice shelf stability 

iC3 team member Tore Hattermann explained that:

"Our study shows how warm ocean water can sneak beneath the ice shelf through eddies, reaching the ice base and contributing to melting. We also see how surface warming in summer influences circulation within the cavity. This highlights the vulnerability of ice shelves like Fimbulisen to climate-driven changes in the ocean.”

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Unique long-term dataset 

The researchers analysed data from three moorings deployed beneath the ice shelf from 2009 to 2023.

These moorings measured temperature, salinity, oxygen, and water velocity at different depths, providing a near-continuous record of conditions within the ice shelf cavity. They combined these measurements with models and advanced statistical methods to map the distribution and movement of water masses. 

This kind of long-term dataset is exceptionally rare, as ice shelf cavities are some of the most difficult environments to study. 

The findings shed new light on how ocean currents interact with ice shelves.

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East Antarctic ice shelves may not be stable 

Fimbulisen is a critical part of the East Antarctic Ice Sheet system, which holds enough ice to raise global sea levels by 3.1 metres.

While this ice shelf experiences lower melt rates than those in West Antarctica, the study confirms that warm water intrusions can significantly increase melting over time. 

The team observed a regime shift in 2016, with more frequent warm water inflows and nearly doubled basal melting rates compared to previous years.

These insights challenge assumptions that East Antarctic ice shelves are stable.

Instead, the research underscores that even minor changes in ocean currents and temperatures could have outsized effects on ice shelf thinning.

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Future sea level rise 

The study has important implications for global climate adaptation efforts.

The Antarctic Ice Sheet is currently the largest uncertainty in projections of future sea level rise.

According to Tore Hattermann: 

"This paper highlights the importance of sustained monitoring. This data can help us to understand how quickly the ice sheet could respond to climate change, and to refine models of future sea level rise."

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If you want to apply for funding to do postdoctoral research into ice-ocean interactions in Antarctica, please check out iC3’s MSCA funding support programme and then email Tore Hattermann.

The study “Hydrography and circulation below Fimbulisen Ice Shelf, East Antarctica, from 14 years of moored observations” was published open access in the journal Ocean Science. Julius Lauber, the lead author, is a researcher at the Norwegian Polar Institute, an iC3 partner institution. iC3 team member Tore Hattermann contributed to the research. Image credits: Tore Hattermann.