Rewritten Article on Antarctic Ocean Acidification and MPAs

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Acidity in coastal waters around Antarctica is rising rapidly. Research from the University of Colorado Boulder warns that by century’s end, the Southern Ocean could see a sharp jump in acidity that threatens whales, penguins, and hundreds of other species that call these waters home.

Predictions indicate that by 2100 the upper 200 meters of the ocean, where most marine life thrives, may become more acidic than the levels measured in the 1990s by more than 100 percent. This finding appears in Nature Communications.

Insights from Nicole Lovenduski, co-author of the study and interim director of the CU Boulder Institute for Arctic and Alpine Research, emphasize that these results are crucial for understanding future trends in marine ecosystem health.

Oceans play a key role as a buffer against climate change, absorbing almost 30 percent of global CO2 emissions. As more carbon dioxide dissolves in seawater, the ocean becomes more acidic, altering the chemistry of marine habitats.

Ice decline in Antarctica — a topic highlighted by researchers and supported by related agencies — underscores the fragility of this system.

Cara Nissen, the study’s first author and an INSTAAR research scientist, notes that human CO2 emissions lie at the heart of ocean acidification.

The Southern Ocean around Antarctica is especially prone to acidification, a consequence partly explained by the cold water’s greater capacity to absorb CO2 and by regional ocean currents that shape the water’s acidity.

Using a computer model, Nissen, Lovenduski, and their team simulated 21st-century changes in Southern Ocean seawater and found that acidity would rise by 2100, with far worse outcomes if emissions are not reduced.

Both the surface and bottom of the ocean

This phenomenon extends beyond the surface. The entire water column along the Southern Ocean coast, including deeper layers, could experience significant acidification, according to the researchers.

The team also explored the management of human activity in this region. Marine protected areas, including those near Antarctica, are intended to safeguard biodiversity by limiting activities such as fishing.

They note that current and planned MPAs would still face substantial acidification by century’s end.

For example, in a scenario with higher emissions, the Ross Sea region, the world’s largest MPA located at the northern edge of Antarctica, could see acidity rise by more than 100 percent from 1990 to 2100. In a mid-range emissions scenario, increases could reach around 43 percent.

Nissen expresses surprise at the severity of potential ocean acidification in these coastal waters.

Phytoplankton is in danger

Phytoplankton, a foundational group of algae driving the marine food web, tends to grow more slowly or perish when waters become too acidic.

Moreover, acidic conditions can weaken shells of organisms such as snails and sea urchins.

These shifts may disrupt the food web and ultimately affect top predators like whales and penguins.

The Weddell Sea, one of three proposed MPAs near the Antarctic Peninsula, is described as a potential climate change refuge for some organisms because it has the highest sea ice cover in Antarctica.

Ice acts as a shield against warming, helping to limit the ocean’s uptake of atmospheric CO2 and slowing acidification. Yet models indicate that as the planet warms, sea ice will decline and the Weddell Sea region will experience ongoing acidification in both medium and high emission scenarios, though progress may be delayed compared to other regions.

Nissen argues that the Weddell Sea region should be prioritized as a protected area. Lovenduski adds that Antarctic coastal zones can act as channels for climate signals reaching the global deep ocean, and changes here can trigger rapid shifts elsewhere.

The study argues that avoiding severe acidification of the Southern Ocean hinges on pursuing a lowest-emissions pathway with rapid, aggressive CO2 reductions.

Reference work: Nature Communications report on Antarctic coastal acidification.

These findings highlight an urgent need for robust ocean stewardship and climate policy that protects critical marine ecosystems while balancing environmental and economic interests.

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