Ocean acidity increased 8.6 percent in New Zealand’s subantarctic surface waters

What is measured

Ocean acidification describes the long-term decrease in the pH of our oceans and coastal waters. This indicator measures:

  • change in pH, acidity, and pCO(partial pressure CO2, which is a measure of dissolved carbon dioxide) in New Zealand’s subantarctic surface waters (Munida Transect) from 1998 to 2020
  • pH at selected coastal sites (New Zealand Ocean Acidification Observing Network, NZOA-ON) from 2015 to 2021.

Why it is important

The oceans are a large carbon sink and have very likely absorbed 20–30 percent of the carbon dioxide (CO2) emitted by human activities in the last two decades (Bindoff et al., 2019). CO2 absorption reduces atmospheric greenhouse gas concentrations. However, when seawater absorbs CO2 from the atmosphere, chemical reactions produce hydrogen ions that acidify the seawater and decrease its pH.

StatsNZ, 25 August 2022. Press release.

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