Consequences of accelerating Antarctic climate change

Antarctica and the Southern Ocean are keystone components of Earth’s climate system due to their central role in distributing energy, influencing weather, and managing sea levels. Antarctica acts as both a recorder of past conditions and a driver of present-day atmospheric and oceanic processes. Recent events including stratospheric warmings and unprecedented sea ice loss have significant impacts beyond the frozen continent, while projections for melting ice sheets and slowing ocean circulation signal challenges and uncertainties for our warming planet. Evidence is mounting that major components of the Antarctic climate system are undergoing rapid and irreversible changes that will increase with every increment of global warming (Abram et al 2025).

The Antarctic Circumpolar Current

One of Antarctica’s most striking features are its vast ice sheets; they began to grow around 34 million years ago when the Drake passage opened and the Antarctic Circumpolar Current formed. This thermally isolated Antarctica, analogous to shutting the freezer door. The Antarctic Circumpolar Current is the largest and strongest of all ocean currents, extending from the surface to the bottom of the ocean. It connects all major ocean basins and plays a crucial role in transporting carbon and heat, thereby regulating global temperature. 

As the climate system and Southern Ocean warms, the Antarctic Circumpolar Current has been expected to accelerate due to increased temperature gradients, stronger winds and more buoyant surface water (Shi et al 2021). However, observations to-date have not shown this, and recent research proposed it should instead slow down due to the influx of fresh water from melting ice sheets; Sohail et al (2025) estimate it could slow 20% by 2050. This would have far-reaching implications including reducing biodiversity and ocean productivity and increasing entry of invasive species.  Penetration of warmer water to higher latitudes could also worsen melting of Antarctic ice shelves. Due to the Antarctic Circumpolar Current’s crucial role in global thermohaline circulation, a slowdown will likely affect all major ocean basins.

Sea level

Ice sheets cover 98% of the Antarctic continent, with an area of ~14 million square kilometres and an average thickness of over 2 kilometres, the Antarctic ice sheets contain ~60% of all fresh water on Earth. Hypothetically, if they melted completely, sea level would rise by about 58 meters. Melting to-date of the Antarctic ice sheets (Figure 1), along with Greenland’s ice sheet, is responsible for about one-third of observed global sea level rise. Current projections suggest we could see 1–2 meters of sea level rise by 2100, depending on global emissions and the behaviour of ice shelves.

Ice shelves are large, floating extensions of land-based glaciers; there are roughly 15 major ice shelves fringing Antarctica’s coastline that act as buttresses, slowing the flow of inland ice toward the ocean. While they appear solid from above, most of their melting occurs from below, where relatively warm ocean water erodes them from the underside. This can contribute to rapid disintegration such as the spectacular collapse of the Larsen B ice shelf in 2002.

As ice shelves thin and break apart, they reduce the friction holding back land ice, allowing glaciers to accelerate toward the sea. This is particularly significant for West Antarctica (Risk Frontiers, 2023a, 2022, 2018) where most of the ice sheet is grounded below sea level and appears to be in irreversible decline (e.g., Naughten et al 2023,  Chandler et al 2025). Recent paleoclimate evidence shows that parts of the East Antarctic Ice Sheet are also susceptible to rapid retreat due to ice shelf collapse (Suganuma et al 2025). According to Stokes et al (2025), ice sheet melting and sea level rise will likely become unmanageable once global warming exceeds 1.5°C above pre-industrial levels. Unfortunately this may have already happened, with Copernicus Climate Change Service advising 3-year average temperatures are set to exceed 1.5°C in 2025 (Symons 2025)

Sea ice

The ongoing deficit in Antarctic sea ice is one of many record-breaking events dominating climate news in recent years. While Arctic sea ice extent has been declining for over 100 years, Antarctic sea ice appeared to be immune until recently. Sea ice extent was increasing until 2016, at which point the positive trend abruptly reversed, culminating in 2022 having the lowest sea ice extent on record, until 2023, and then 2024 (Figure 2), that may be attributable to wind anomalies (Risk Frontiers, 2023b). The trend has continued with 2025 having the third lowest maximum sea ice extent on record (NSIDC 2025) leading researchers to suggest that a regime shift is under way in the Southern Ocean (Hobbs et al 2024).

If the current decline continues, impacts could be profound. Although melting sea ice does not itself raise sea levels because it is already floating, it does perform critical climate and ecosystem functions. Loss of ice reduces the amount of solar energy that is reflected back to space, causing more warming of the ocean. Antarctic sea ice also influences the way in which the ocean circulates oxygen, nutrients, and energy around the globe. By buffering waves, Antarctic sea ice protects the ice shelves that are attached to the land. Without the sea ice, the rate at which the ice shelves break up could accelerate, which would increase global sea levels and have much more pronounced impacts on the climate system. 

Southern Ocean Clouds

The Southern Ocean is one of the cloudiest regions on earth, where they play a fundamental and complex role, acting as both regulators of energy and as one of the largest sources of uncertainty in climate projections. Clouds influence the planet’s energy balance by reflecting incoming sunlight back to space (a cooling effect) and trapping heat emitted from the surface (a warming effect), depending on cloud type and microphysical properties. 

Satellite observations from the past 24 years suggest that midlatitude cloud zones are contracting at a rate of 1.5–3% per decade (Tselioudis et al., 2025). This reduction is now understood to be the largest contributor to Earth’s increased absorption of solar radiation, accelerating surface warming, and potentially driving faster changes in Antarctic atmospheric and oceanic circulation than previously expected. 

Quantifying the impacts is challenging because climate models continue to struggle with representing mixed-phase (both liquid and ice) clouds in the Southern Ocean. Improving their representation is crucial, as cloud feedbacks over the Southern Ocean influence ice-albedo processes, surface warming, ocean heat uptake, and even atmospheric circulation patterns that affect climate, and climate-change projections, worldwide (Logan, 2025).

The Stratosphere

High in the stratosphere, between 15 to 35 kilometers above Earth’s surface, the ozone layer protects life on earth by absorbing harmful ultraviolet (UV) radiation. 40-years ago scientists from the British Antarctic Survey (BAS) – Joe Farman, Brian Gardiner and Jon Shanklin published one of the most important scientific discoveries in human history. They discovered a dramatic thinning of the ozone layer over Antarctica in springtime, and the culprit was human activity, specifically the emission of chlorofluorocarbons (CFCs) into the atmosphere. There was a rapid global consensus that destroying ozone was undesirable, so the Montreal Protocol effectively eliminated most sources of ozone destroying chemicals—a major win for science-led policy.

Modelling experiments conducted by Newman et al (2009) show that had we continued to destroy the Ozone layer, our world would be a very different place right now. It would be dangerous to spend much time outside, and the ecological damage would have been catastrophic. Fast forward to 2026 and ozone levels are slowly recovering; they are expected to return to pre-1980 levels by ~2060. This recovery will apparently offset global warming by up to 0.5°C by the end of the century (UNEP 2023). At present there are still large year-to-year fluctuations, for example 2019 and 2025 had much smaller ozone holes compared to 2018 and 2020—but this apparent recovery is linked to another concerning phenomena.

Since 2019, Antarctica has experienced three sudden stratospheric warming events, where temperatures in the stratosphere over Antarctica can suddenly increase by >30 degrees (Lim et al 2023; Zi et al 2025; Jucker 2025). These events are common in the northern hemisphere, but prior to 2019 were almost unprecedented in the southern hemisphere, with only one previously observed in 2002. Sudden warming events can affect Australian weather by perturbing the the circumpolar vortex. They tend to cause a weakening of the circumpolar westerlies and a shift to the strongly negative phase of the Southern Annual Mode. Under these conditions, the westerly storm track can become more meridional and push further north in some regions. For southeast Australia they have resulted in more fronts and stronger winds during springtime, which can dry the landscape and increase bushfire risk. The recent September stratospheric warming event may have contributed to Spring 2025 being the windiest on record above southeast Australia (Figure 3).

Since 2019 sudden stratospheric warmings have been implicated in driving severe bushfire weather in 2019-2020 and flow-on effects (Lim et al 2025; Risk Frontiers 2023c), an early end to the snow season and severe weather outbreak over Tasmania in 2024 (Risk Frontiers 2024), and exceptionally windy conditions over south eastern Australia that have confounded seasonal forecasting and increased summer bushfire risk in 2025 (Saunders 2025; Domensino 2025). Sudden stratospheric warming events are only expected to occur about once every 22 years, yet we have seen 3 in the past 7 years. Zi et al (2025) show that substantial sea ice loss in 2024 likely affected tropospheric circulation creating favourable conditions for the formation of multiple sudden warming events. If these are becoming more frequent in a warmer climate, then we urgently need further research to understand the implications for Australia.

Conclusion

From the deep ocean to the stratosphere, Antarctica’s climate system is undergoing profound changes. Many of the observed changes discussed here, such as melting ice sheets and reduced sea ice extent, are closely linked to increasing global temperatures and effectively irreversible on human timescales. Impacts of these changes will be increasingly felt far from the frozen continent but are especially relevant to Australia, as we sit on Antarctica’s doorstep.

There are some good news stories, such as ozone recovery; concerning stories, such as sea ice decline and sea level rise; and areas where we clearly do not know enough, such as the Antarctic Circumpolar Current and stratospheric warming events. Australia has a long history of Antarctic monitoring and research that will need to continue if we hope to understand and adapt to these changes.

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