Antarctica has long been perceived as a remote and unchanging environment. However, this notion is rapidly becoming obsolete. The ice-covered continent and the surrounding Southern Ocean are experiencing abrupt and alarming changes. Evidence shows that sea ice is shrinking at an unprecedented rate, floating glaciers known as ice shelves are melting faster than anticipated, ice sheets are nearing their tipping points, and crucial ocean currents are displaying concerning signs of slowing down.
Published recently in the journal Nature, our research indicates that these changes are not only underway but are likely to escalate significantly in the future. Several authors involved in this study have personally witnessed these startling transformations during their fieldwork on the ice. The implications of these changes are dire, affecting both iconic wildlife species and lesser-known organisms. The consequences of what is happening in Antarctica will resonate worldwide for generations, leading to rising sea levels and extreme shifts in the climate system.
But what exactly constitutes an abrupt change? Scientists define it as a climatic or environmental shift occurring much faster than expected. The concerning aspect of abrupt changes is their potential to amplify themselves. For instance, as sea ice melts, oceans absorb heat more rapidly, which in turn leads to further sea ice melting. Once triggered, these changes can be challenging or even impossible to reverse within a human timeframe.
Typically, it is assumed that incremental warming will result in gradual changes; however, the situation in Antarctica reveals a much different reality. For decades, the Antarctic environment had a muted response to human-induced climate warming compared to the Arctic. Yet, around a decade ago, we began to observe the onset of abrupt changes.
Antarctica's natural systems are intricately interconnected. A disturbance in one system can trigger a cascade of effects in others. Since 2014, sea ice around Antarctica has been declining dramatically, now shrinking at double the rate of Arctic sea ice. Our findings demonstrate that these changes are unprecedented and far beyond the natural variability observed in past centuries. The implications are extensive; sea ice has a reflective, high-albedo surface that helps radiate heat back into space. With less sea ice, more heat is absorbed by the darker ocean waters, posing significant threats to species like emperor penguins that rely on sea ice for habitat and breeding.
The melting of ice is also causing a slowdown in the deep ocean circulation around Antarctica. This system, known as the Antarctic Overturning Circulation, plays a pivotal role in regulating Earth's climate by absorbing carbon dioxide and distributing heat. Currently, we are observing a similar risk to the Southern Ocean currents as seen with the slowing of the Atlantic Meridional Overturning Circulation in the Northern Hemisphere. Changes to the Antarctic Overturning Circulation may occur at twice the rate of its Northern counterpart, potentially reducing the ocean's capacity to absorb oxygen and carbon dioxide, which could have devastating effects on marine ecosystems.
The West Antarctic Ice Sheet and certain regions of East Antarctica are now losing ice and contributing significantly to global sea level rise. Since the 1990s, ice loss has increased sixfold. The West Antarctic Ice Sheet alone contains enough ice to elevate global sea levels by over five meters. Scientists warn we may be approaching a point where this ice sheet could collapse even without significant additional warming, although this process could take centuries to millennia. These massive ice sheets represent a potential global tipping point, introducing considerable uncertainty into projections of future sea level rise, as we remain unclear on the rate at which they may collapse.
Antarctica's biological systems are also facing sudden and potentially irreversible changes. Ecosystems both underwater and on land are being reshaped by rising temperatures, unstable ice conditions, and human activities that introduce pollution and invasive species. Protecting these ecosystems is essential and requires adherence to the Antarctic Treaty, which calls for the establishment of protected areas and restrictions on certain human activities. However, these conservation measures alone may not suffice to ensure the survival of species such as emperor penguins and leopard seals; decisive global action to reduce greenhouse gas emissions is crucial.
Historically viewed as a symbol of isolation and permanence, Antarctica is now experiencing changes at an alarming speed—much faster than scientists had anticipated. These abrupt changes are primarily driven by the excess heat trapped from decades of unchecked greenhouse gas emissions. To avoid further abrupt changes, it is imperative to rapidly reduce emissions and aim to limit warming as close to 1.5°C as possible. Even if we manage to achieve this, significant changes are already set into motion.
Governments, businesses, and coastal communities must prepare for a future marked by abrupt changes. The events unfolding in Antarctica will not remain confined to its icy shores; they will have global repercussions. The stakes have never been higher, and the decisions we make today will determine whether we face escalating impacts and irreversible changes or if we can foster resilience against the changes that are already locked in.
Contributors to this research include Nerilie Abram, Chief Scientist at the Australian Antarctic Division and Professor of Climate Science at the Australian National University; Ariaan Purich, Senior Lecturer in Climate Science at Monash University; Felicity McCormack, Antarctic Research Fellow and Senior Lecturer at Monash University; Jan Strugnell, Professor of Marine Biology and Aquaculture at James Cook University; and Matthew England, Deputy Director of the ARC Australian Centre for Excellence in Antarctic Science and Scientia Professor in Oceanography at UNSW Sydney.
