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Most people will never see Antarctic sea ice up close, but its presence or absence affects our day-to-day lives.

Now scientists are questioning whether a ‘regime shift’ to a new state of diminished Antarctic sea-ice coverage is underway, due to recent record lows.

If so, it will have impacts across climate, ecological and societal systems, according to new research published in PNAS Nexus.

These impacts include ocean warming, increased iceberg calving, habitat loss and sea-level rise, and effects on fisheries, Antarctic tourism, and even the mental health of the global human population.

Led by Australian Antarctic Program Partnership oceanographer Dr Edward Doddridge, the international team assessed the impacts of extreme summer sea-ice lows, and the challenges to predicting and mitigating change.

“Antarctic sea ice provides climate and ecosystem services of regional and global significance,” Dr Doddridge said.

“There are far reaching negative impacts caused by sea-ice loss.

“However, we do not sufficiently understand the baseline system to be able to predict how it will respond to the dramatic changes we are already observing.

“To predict future changes, and to potentially mitigate the negative impacts of climate change on Antarctica, we urgently need to improve our knowledge through new observations and modelling studies.”

What’s at stake?

While sea-ice loss affects many things, the research team identified three key impacts:

• Reduced summer sea-ice cover exposes more of the ocean to sunlight. This leads to surface water warming that promotes further sea-ice loss. Ocean warming increases melting under glacial ice shelves, which could lead to increased iceberg calving. Warmer water also affects the flow of deep-water currents that help move ocean heat around the globe, influencing the planet’s climate.
• Sea-ice loss exposes the ice shelves that fringe the Antarctic continent to damaging ocean swells and storms. These can weaken the ice shelves, leading to iceberg calving. As ice shelves slow the flow of ice from the interior of the Antarctic continent to the coast, iceberg calving allows this interior ice flow to speed up, contributing to sea-level rise.
• Sea ice provides breeding habitat for penguin and seal species, and a refuge for many marine species from predators. It is also an important nursery habitat and source of food (sea-ice algae) for Antarctic krill – an important prey species for many Southern Ocean inhabitants. Adverse sea-ice conditions that persist over several seasons could see population declines in these sea-ice dependent species.

The research team also identified socio-economic and wellbeing impacts, affecting fisheries, tourism, scientific research, ice-navigation, coastal operations, and the mental health (climate anxiety) of the global population.

For example, shorter sea-ice seasons will reduce the window for over-ice resupplies of Antarctic stations. There could also be increased shipping pressures on the continent, including from alien species incursions, fuel spills and an increase in the number and movement of tourist vessels to and from new locations.

Research co-author and sea-ice system expert, Dr Petra Heil, from the Australian Antarctic Division, said the paper highlighted the need for ongoing, year-round, field-based and satellite measurements of circumpolar sea-ice variables (especially thickness), and sub-surface ocean variables.

This would allow integrated analyses of the Southern Ocean processes contributing to the recent sea-ice deficits.

“As shown in climate simulations, continued greenhouse gas emissions, even at reduced rate, will further accelerate persistent deficits of sea ice, and with it a lack of the critical climate and ecosystem functions it provides,” Dr Heil said.

“To conserve and preserve the physical environment and ecosystems of Antarctica and the Southern Ocean we must prioritise an immediate and sustained transition to net zero greenhouse gas emissions.

“Ultimately our decison for immediate and deep action will provide the maximum future proofing we can have in terms of lifestyle and economic values.”

Learn more about Antarctic sea ice in our feature Sea ice in crisis.

Using the Mid-InfraRed Instrument (MIRI) aboard the NASA/ESA/CSA James Webb Space Telescope, astronomers have captured a stunning infrared image of central part of Messier 82, an edge-on starburst galaxy located about 12 million light-years away.

Messier 82 appears high in the northern spring sky in the direction of the constellation of Ursa Major.

First discovered by the German astronomer Johann Elert Bode in 1774, this galaxy is approximately 40,000 light-years across.

Messier 82 is also called the Cigar Galaxy because of the elongated elliptical shape produced by the tilt of its starry disk relative to our line of sight.

The galaxy is famous for its extraordinary speed in making new stars, with stars being born 10 times faster than in our Milky Way Galaxy.

“Despite being smaller than the Milky Way, Messier 82 is five times as luminous as our home Galaxy and forms stars ten times faster,” Webb astronomers said in a statement.

“Messier 82 is classified as a starburst galaxy because it is forming new stars at a rate much faster than expected for a galaxy of its size, especially at its center.”

In visible-light images of Messier 82, the central hotbed of activity is obscured by a network of thick and dusty clouds, but Webb’s infrared eyes are designed to peer through this cloudy veil and reveal the activity behind them.

“What caused Messier 82’s burst of star formation? The answer likely lies with its neighbor, the larger spiral galaxy Messier 81,” the astronomers said.

“We suspect that the two galaxies have interacted gravitationally, sending gas pouring into Messier 82’s center millions of years ago.”

“The influx of gas provided the raw material for new stars to form — and form they did! Messier 82 is home to more than 100 super star clusters, some of which are still in the process of forming and are blanketed with dense, dusty gas.”

“Super star clusters are more massive and luminous than typical star clusters; these ones each contain around 100,000 stars.”

A previous Webb image of Messier 82, featuring data from the telescope’s Near-InfraRed Camera (NIRCam), was released in 2024.

It focused on the very core of the galaxy, where individual clusters of young stars stand out against the clumps and tendrils of gas.

The new image, captured by Webb’s MIRI instrument, provides a remarkable, mostly starless view of Messier 82.

“The image is instead dominated by the emission from warm dust and intricate clouds of sooty organic molecules called polycyclic aromatic hydrocarbons or PAHs,” the researchers said.

“The emission from the PAH molecules traces the galaxy’s broad outflows, which are launched by the intense radiation and winds from the hot young stars of the central super star clusters.”

“Though super star clusters are the source of Messier 82’s powerful galactic winds, the winds may spell the end for the galaxy’s starburst era: as the winds billow into intergalactic space, they likely carry with them the cool gas needed to form even more stars.”

New research has for the first time tracked ice shelf, sea ice and ocean swell wave conditions over multiple years in the lead-ups to three large-scale iceberg ‘calving’ events in Antarctica, revealing common patterns.

Iceberg calving is the process where chunks of ice break off from glaciers, ice shelves, or icebergs, and fall into the surrounding water.

Published in Nature Geoscience, the study, led by the Universities of Melbourne and Adelaide, found long periods of sea ice loss surrounding the ice shelves in the six to 18 months prior to calving, as well as the collapse of the ‘landfast’ sea ice attached to the ice shelves only weeks prior to the calving events.

University of Melbourne Professor Luke Bennetts explained that the researchers also developed a novel mathematical model to quantify the ice shelf flexing caused by the huge Southern Ocean swells.

“Sea ice is retreating at an unprecedented rate all around Antarctica and our work suggests this will put further pressure on already thinned and weakened ice shelves,” Professor Bennetts said.

“This could lead to more large-scale calving events, with profound implications for the future of global sea levels.”

The Antarctic Ice Sheet is the thick layer of ice that sits on top of Antarctica. It holds enough fresh water to raise current sea levels by over 50 metres.

Ice shelves are floating platforms formed as glaciers flow off the Antarctic continent onto the ocean, whereas sea ice forms when the surface of the ocean freezes.

“Except for a relatively short period around summer, sea ice creates a protective barrier between the ice shelves and the potentially damaging swells of the Southern Ocean,” Professor Bennetts said.

“Without this barrier, the swells can bend and flex pre-weakened ice shelves until they break.”

Professor Bennetts said previous research has shown that warming temperatures are causing more rapid melting and more frequent ‘calving’ of icebergs from some ice shelves.

“Increased melting and calving does not directly increase sea levels as the ice shelves are already floating on the ocean, but it reduces the ability of the ice shelves to push back against the glacial flow into the ocean – which does raise sea levels,” he said.

There is currently no observation system for routinely recording ocean waves in Antarctic sea ice and ice shelves, so mathematical modelling is essential to quantify the connection between the observed ocean swells, sea ice conditions and the response of the ice shelves.

The research was funded by the Australian Antarctic Science Program and the Australian Research Council and collaborators included the University of Melbourne, the University of Adelaide, the Australian Bureau of Meteorology, the University of Tasmania, and the Australian Antarctic Division.