ACIDITY OF ANTARCTIC WATERS COULD DOUBLE BY CENTURY’S END

Scientists projected that by 2100, the upper 650 feet (200 meters) of the ocean — where much marine life resides — could see more than a 100% increase in acidity compared with 1990s levels.

The paper, appeared Jan. 4 in the journal Nature Communications.

“The findings are critical for our understanding of the future evolution of marine ecosystem health,” said Nicole Lovenduski, the paper’s co-author and the interim director of CU Boulder’s Institute of Arctic and Alpine Research (INSTAAR).

The oceans play an important role as a buffer against climate change by absorbing nearly 30% of the CO₂ emitted worldwide.

But as more CO₂ dissolves in the oceans, the seawater becomes more acidic.

“Human-caused CO₂ emissions are at the heart of ocean acidification,” said Cara Nissen, the paper’s first author and a research scientist at INSTAAR.

The Southern Ocean, which surrounds Antarctica, is particularly susceptible to acidification, partly because colder water tends to absorb more CO₂. Ocean currents in the area also contribute to the relatively acidic water conditions.

Using a computer model, Nissen, Lovenduski and the team simulated how the seawater of the Southern Ocean would change in the 21st century.

They found it would become more acidic by 2100, and the situation would be severe if the world fails to cut emissions.

“It’s not just the top layer of the ocean. The entire water column of the coastal Southern Ocean, even at the bottom, could experience severe acidification,” Nissen said.

The team then investigated the conditions specifically in Antarctica’s marine protected areas (MPAs). Human activities, such as fishing, are restricted in these regions to protect biodiversity.

Currently, there are two MPAs in the Southern Ocean, covering about 12% of water in the region.

Scientists have proposed designating three more MPAs to an international council in the past years, which would encompass about 60% of the Antarctic Ocean.

The team’s model showed that both adopted and proposed MPAs would experience significant acidification by the end of the century.

For example, under the highest-emission scenario, where the world makes no efforts to cut emissions, the average acidity of the water in the Ross Sea region — the world’s largest MPA off the northern tip of Antarctica — would increase by 104% over 1990s levels by 2100.

Materials provided by University of Colorado at Boulder. Original written by Yvaine Ye.