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Our oceans and the climate

New Zealand’s seas are part of the vast interconnected system of water that makes up Earth’s ocean, covering about 70 percent of the planet. The ocean is part of a very complex natural system, which for thousands of years has provided the planet with a stable climate favourable to human life. Two critical roles the ocean has in the climate system are the capture and storage of carbon and the regulation of global temperature.

This chapter is about human activities that, on a global scale, are changing the ocean and wider climate system, including here in New Zealand. Global greenhouse gas emissions are increasing the concentration of these gases in the atmosphere, warming the atmosphere and ocean, and causing sea levels to rise. As well as having a warming effect, some of the additional atmospheric carbon dioxide is being absorbed by the ocean, causing it to acidify.

Ocean acidification and a warmer ocean are serious threats to New Zealand’s marine ecosystems, and subsequently, to commercial and recreational fishing and aquaculture.

We report on global greenhouse gas emissions, concentrations of greenhouse gases in the atmosphere, ocean acidification, sea-surface temperature, and coastal sea levels.

Top issue

Greenhouse gas emissions are causing ocean acidification and warming

Ocean acidification

The world’s oceans are absorbing some of the additional carbon dioxide in the atmosphere from global carbon dioxide emissions, causing them to become more acidic. New Zealand’s ocean waters are also becoming more acidic.

Ocean acidification will continue for generations as long as substantial carbon dioxide emissions continue. In the future, ocean acidification may cause widespread harm to species and ecosystems across our marine environment.

Ocean warming

High concentrations of global greenhouse gas emissions are warming the planet, including the world’s oceans. New Zealand’s oceans are warming at a similar rate as the world’s oceans.

Ocean warming will continue for centuries to millennia even if atmospheric greenhouse gas concentrations are stabilised. Ocean warming may extend or reduce the range of marine species and modify marine habitats. In the future it may cause widespread harm to marine ecosystems. Ocean warming is a primary cause of rising sea levels.