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Study published in Science Advances explains how deep heat, intense winds, and saltier water created a cycle of low sea ice in Antarctica.
According to CNN, a study published on May 8, 2026, in the journal Science Advances, led by researchers from the University of Southampton, identified the mechanism behind the collapse of Antarctic sea ice that has concerned scientists since 2015. For decades, sea ice around Antarctica defied the global warming trend, growing even as the Arctic rapidly melted. From 2015 onwards, this behavior changed abruptly. In 2023, the collapse eliminated an area of ice equivalent to the size of Greenland, bringing the extent of Antarctic sea ice to the lowest level since satellite measurements began.
The study, led by oceanographer Aditya Narayanan, shows that the collapse occurred in three phases connected over a decade. First, there was a slow accumulation of heat at the ocean’s bottom; then, intense winds mixed this heat with the surface; finally, since 2018, the system entered a cycle where the ocean became too warm and salty for the ice to recover.
Antarctic sea ice collapsed after decades defying the global warming trend
Antarctic sea ice has always intrigued climate science because, for a long time, it did not follow the same pattern as the Arctic. While the northern planet’s ice rapidly shrank with global warming, the ice cover around Antarctica showed growth or relative stability.
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This difference fueled debates about winds, ocean currents, salinity, and natural variability in the Southern Ocean. However, the turn in 2015 changed the picture: the ice began to decline persistently, with negative records in the following years.
The University of Southampton study indicates that this change was not the result of a single isolated event. The collapse of Antarctic sea ice was born from a sequence of mutually reinforcing physical processes, making recovery more difficult.
Accumulated heat at the bottom of the Southern Ocean was the first invisible trigger of the collapse
The first phase of the process was practically invisible on the surface. Warm, salty water from the Deep Circumpolar Current began to accumulate at the ocean’s bottom under the ice over several years.
This deep water has always existed in the Southern Ocean, but it usually remains away from the surface. However, with global warming, it became warmer, and its presence in the deep layers gradually intensified.
This accumulation created a heat reserve under the Antarctic ice. The system became vulnerable: a mechanism capable of mixing this deep water with the surface was enough to accelerate the melting.
Intense winds in 2015 pulled warm water to the surface and melted the ice quickly
The second phase occurred in 2015, when westerly winds became stronger than usual. These winds mixed the ocean layers and pulled warm water from the bottom towards the surface.
Upon contacting the base of the sea ice, this water accelerated the melting. The impact was especially strong in East Antarctica, where the ocean mixing mechanism played a central role in the ice loss.
In West Antarctica, the study identified another important factor. An intense cloud cover trapped heat coming from the subtropics and contributed to the ice melting in the summers of 2016 and 2019.
Warmer and saltier water since 2018 stalled the recovery of Antarctic sea ice
The third phase is the most concerning because it created a feedback loop. With less ice available to melt, the ocean surface became warmer and saltier.
Saltier water freezes at a lower temperature. This means that even with the arrival of the Antarctic winter, the sea surface does not refreeze with the same intensity observed previously.
The result is a system trapped under low ice. Less ice makes the ocean darker, warmer, and saltier; this warmer and saltier ocean prevents the formation of new ice in sufficient volume.
Antarctic ice acts as a climate mirror and reflects up to 80% of solar light
Antarctic sea ice matters for the global climate because its white surface reflects a large part of the solar radiation back into space. According to the base text, this reflection can reach up to 80% of the received light.
When the ice disappears, the dark ocean is exposed and absorbs more heat. This additional warming increases the water temperature and hinders the recovery of the frozen cover.
This process is one of the most important feedbacks of the polar system. The ice helps cool the planet; when it shrinks, the ocean itself starts to absorb more energy and reinforce the warming.
Loss of sea ice can affect ocean currents and sea level
Sea ice also participates in the thermohaline circulation, the great global ocean current that distributes heat, salt, and oxygen throughout the oceans. When water freezes near Antarctica, the remaining salt increases the water’s density, causing it to sink.
This sinking helps drive the deep circulation of the oceans. With less ice forming, this mechanism can weaken, altering the distribution of heat and nutrients on a planetary scale.
Furthermore, a warmer Southern Ocean can erode the ice shelves attached to the continent from below. This facilitates the advance of land glaciers into the sea, contributing to the rise in sea levels.
Low Antarctic ice until 2030 could transform the Southern Ocean into a driver of global warming
Researchers warn that the risk increases if the low ice cover persists until 2030 and beyond. Alberto Naveira Garabato, professor of physical oceanography and co-author of the study, stated that the ocean may cease to act as a climate stabilizer and start functioning as a new driver of global warming.
The Southern Ocean has historically absorbed heat and carbon dioxide from the atmosphere, acting as one of the planet’s main climate buffers. In a scenario of persistently low sea ice, this function may be weakened.
Alessandro Silvano, also a co-author of the study, highlighted that the problem is not just regional. The loss of Antarctic sea ice can affect ocean currents, ice shelves, glaciers, and sea level rise projections.
Global warming amplifies winds, ocean heat, and difficulty in ice formation
The study distinguishes natural variability and long-term climate influence. Deep warm water has always existed in the Southern Ocean, and strong winds have always been part of the region’s dynamics.
What has changed is the intensity of the system. Global warming adds more heat to the deep waters, makes mixing episodes more destructive, and makes it difficult for the surface to cool sufficiently during winter.
Narayanan summarized the mechanism by stating that long-term climate-driven changes can trigger a cascade of processes that push the system into a prolonged low-ice state. The negative record of 2023 does not appear as an isolated event, but as a consequence of a sequence initiated years earlier.
Collapse of Antarctic sea ice reveals risk of a climate cycle difficult to reverse
The main message of the study is that Antarctic sea ice may have entered a more difficult recovery phase. The system has stopped responding solely to the seasonal winter and summer cycle and has begun to carry thermal and saline memory from previous years.
This memory makes the ocean less favorable for the formation of new ice. Even when atmospheric conditions change temporarily, the warmer and saltier surface water continues to hinder the return to historical levels.
The researchers’ warning is direct: what started as a slow accumulation of heat at the sea bottom evolved into violent mixing and ended in a vicious cycle of low ice. If this pattern persists, Antarctica may stop being just a victim of global warming and start amplifying part of it.
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