Is the ocean’s ability to regulate the global climate breaking down?

Oceans are a global force of nature that form the foundation of the blue planet on which we live. They cover 71% of our planet’s surface and make up 95% of all the space available to life. They are a life-support system for Earth and a global commons that provide us with free goods and ecological services, from the food we eat to the oxygen we breathe.

The oceans also regulate the global climate; they mediate temperature and drive the weather, determining rainfall, droughts, and floods. They are also the world’s largest store of carbon, where an estimated 83% of the global carbon cycle is circulated through marine waters.

The oceans take up more than 90% of the heat trapped by greenhouse gases. For the oceans as a whole 50% of the heat taken up since 1865 has occurred since 1997. In other words, the oceans have absorbed as much heat in the past 18 years as in the previous 130 years. While most of the heat stayed in the upper ocean, about 35% found its way to the deep ocean below 700m – and that fraction has increased steadily over time.

Ocean warming leads to deoxygenation – a reduction in the amount of oxygen dissolved in the ocean – and sea-level rise – resulting from the thermal expansion of sea water and continental ice melting. The rising temperatures, coupled with ocean acidification (the decrease in pH of the ocean due to its uptake of CO2), affect marine species and ecosystems and, consequently, the fundamental benefits humans derive from the ocean.

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Sources:

• International Union for the Conservation of Nature (IUCN)

• World Wide Fund for Nature (WWF)