Antarctica’s Ocean Acidification: A Warning to the World 

By Yooan Jung, Yeavon Kim

Antarctica, thought to be an untouched wilderness at the bottom of our planet, shrouded in ice and mystery. To the casual observer, it seems as far removed from human interference as any place on Earth could be. But beneath its frozen surface, the Southern Ocean is undergoing a rapid, perhaps man-induced chemical transformation that could ripple across the globe: ocean acidification.

Oceans act like a giant sponge for atmospheric carbon dioxide (CO₂), absorbing roughly 25–26% of all human-generated emissions. When CO₂ dissolves into seawater, it reacts with water to form carbonic acid, which lowers the pH and strips carbonate ions from the water. These carbonate ions are essential for marine organisms to construct shells and skeletons from calcium carbonate. According to the National Oceanic and Atmospheric Administration (NOAA), since the Industrial Revolution, the average surface pH has dropped below 8.05, a decline of approximately 40% since the pre-industrial era, surpassing any other period within the last 2 million years. Furthermore, the Nature Climate Change journal has reported that, looking at the exponential increase of CO2 emissions, ocean pH is projected to decline even further, between 0.15 and 0.5 by 2100, more than a 150% increase in acidity compared to pre-industrial levels, depending on the emission scenario.

So why focus on Antarctica? It turns out the Southern Ocean is uniquely vulnerable to acidification. Cold water absorbs CO₂ more readily than warm water, and Antarctica’s waters are some of the coldest on Earth. The region alone accounts for about 40% of the ocean’s total carbon uptake, meaning it’s acidifying faster than most of the world’s seas. A study published in Earth and Space Science News (EOS) warned that on the Antarctic continental shelf, anthropogenic carbon levels in the upper 200 meters could rise by over 120 µmol/kg by the end of the century, compared to just ~10 µmol/kg in the open ocean.

The increase in acidity and plummeting of carbonate ions means disaster for shelled creatures living in Antarctica, and anything else that depends on them. Most critical is the Antarctic krill, the foundation of the marine food web. They are eaten by whales, seals, penguins, squid, and fish. According to a study in Polar Biology, seals consume 63–130 million tonnes of krill each year, whales eat 34–43 million tonnes, and seabirds take 15–20 million tonnes. Remove or weaken krill populations, and entire Antarctic ecosystems begin to collapse. Another vulnerable group is pteropods, tiny snail-like plankton that make up as much as 25% of total zooplankton biomass in parts of the Southern Ocean. Their thin aragonite shells begin to dissolve when carbonate ion levels drop, a direct result of rising acidity. Research published in Biogeosciences first documented widespread shell dissolution in pteropods under low-carbonate conditions, underscoring the risks these species face. More recently, a 2025 study led by Dr. Hugh Carter, reported in The Guardian, observed that the aragonite saturation horizon, the depth below which aragonite dissolves, is moving steadily upward toward surface waters in the Southern Ocean. If it reaches the upper sunlit layers, shell-forming species will struggle to survive. The problem extends beyond small organisms. The same study, which compared modern sea urchin shells with those collected over 100 years ago, found that today’s specimens are thinner, weaker, and more brittle, with many disintegrating under light pressure.

But the Southern Ocean, however, does far more than support penguins and seals. It drives global ocean circulation, moving nutrients, oxygen, and heat around the planet. A report in Nature Climate and Atmospheric Science found that the Antarctic bottom water formation, a key driver of this system, has already weakened by 10–20%, reducing its ability to sequester carbon and distribute nutrients. If Antarctic acidification continues unchecked, it could double in severity by 2100 in the upper 200 meters of coastal waters, especially in marine protected areas. A pH drop of 0.3 units represents not just a chemical change but a fundamental restructuring of the marine environment, one unprecedented in millions of years.

Antarctica’s acidification is not an isolated problem. It is a warning bell for the rest of the planet. The collapse of shell-forming plankton could cripple the base of the Southern Ocean food web, sending shockwaves through global fisheries and marine biodiversity. Without significant global CO₂ cuts, the chemical tipping point could be reached within decades, and recovery would take centuries. The world’s last great wilderness is telling us something loud and clear: the time to act is now.