Ocean acidification is a growing concern as it is now reaching marine regions as deep as 1500 meters, posing new threats to various organisms such as sea butterflies, sea snails, and cold-water corals.

The ocean acts as a major carbon dioxide sink, absorbing approximately a quarter of our annual emissions. This absorption leads to increased acidity at the ocean’s surface, impacting sensitive ecosystems like coral reefs. However, the extent to which this acidification is penetrating deeper waters was previously unknown.

Jens Daniel Müller and his team at the Federal Institute of Technology Zurich in Switzerland utilized a 3D model to track the movement of carbon dioxide through the ocean based on global current measurements. By analyzing how carbon dioxide absorption since 1800 has influenced deep-water acidity, they discovered a clear acidification signal down to 1000 meters in most ocean areas, with some regions like the North Atlantic experiencing acidification down to 1500 meters due to the Atlantic meridional overturning current (AMOC).

According to Hongjie Wang from the University of Rhode Island, the data confirming this acidification progression provides valuable insights into the ocean’s response to increased CO2 levels.

The research highlighted that around half of all acidification since 1800 occurred after 1994, indicating a rapid escalation due to exponential CO2 emissions. This escalating acidification poses a significant threat to marine organisms, particularly pteropods like sea snails and sea butterflies that rely on calcium to build their shells, which can dissolve in acidic waters. The rise in acidity also doubles the areas where cold-water corals struggle to survive.

As CO2 emissions continue to rise, ocean acidification is expected to persist, even if emissions were halted immediately. Müller emphasizes that the process of ocean acidification in the interior will continue for hundreds of years.