Ocean Acidification

There is nothing more fundamental to humans than the availability of oxygen. We give little thought to the oxygen we need, we just breathe, but where does it come from?

To shed light on this, statements such as “the ocean provides 50% of the oxygen we breathe”, or its equivalent, “every second breath we breathe comes from the ocean”, have become common mantras to highlight human dependence on the ocean and the risk of lower oxygen supply due to climate change and environmental degradation.

These mantras are repeated by high-profile politicians, including US climate envoy John Kerry and French president Emmanuel Macron, international organisations such as Unesco and the European Commission, and even prominent reports from the IPCC and other reputable scientific institutions.

While they may be good fodder for speeches, these claims misrepresent where the oxygen we breathe actually comes from, and in doing so, mislead the public as to why we should step up our role as ocean custodians.

Where do we get our oxygen?

The Earth’s atmosphere has not always been as rich in oxygen as it is today. The atmosphere is now made up of 21% oxygen, but it accounted for just 0.001% of today’s levels during the first 2 billion years of Earth’s history.

It is the advent of microscopic ocean bacteria and plants (phytoplankton) and, later, larger plants on land which caused the staggering increase of oxygen in our atmosphere. This oxygen is derived from photosynthesis – the process by which plants turn carbon dioxide and water into organic matter and oxygen.

Oxygen has been relatively stable at a high level for the past 500 million years. Today, roughly half of photosynthesis takes place in the ocean and half on land.

So yes, the ocean is responsible for about 50% of the oxygen produced on the planet. But it’s not responsible for 50% of the air we humans breathe. Most of the oxygen produced by the ocean is directly consumed by the microbes and animals that live there, or as plant and animal products fall to the seafloor. In fact, the net production of oxygen in the ocean is close to 0.

A tiny fraction of the primary production, roughly 0.1%, escapes degradation and is stored as organic carbon in marine sediments – a process referred to as the biological carbon pump. This organic carbon may eventually turn into fossil fuels such as coal, oil and gas. The tiny amount of oxygen which had been generated to produce this carbon store can later be released to the atmosphere. A similar process occurs on land too, with some carbon stored in soils.

Therefore, the oxygen we currently breathe comes from the slow accumulation of O₂ in the atmosphere supported by the burial of organic matter over very long time-scales – hundreds of millions of years – and not from the contemporary production by either the land or ocean biosphere.

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• The UN’s IPCC report said climate change is widespread, rapid and intensifying.
• Detailed plans to cut greenhouse gas emissions and concrete commitments to invest in a sustainable blue economy are what’s needed, United Nations’ Special Envoy for the Ocean Peter Thomson said in an interview.
• “You can’t have a healthy planet without a healthy ocean,” he said.
• Ongoing changes to the ocean include warming, marine heatwaves, acidification and reduced oxygen levels.
• Officials attending the COP26 climate summit need to increase their ambition, he said.

“Ramp it up” and “deliver us from this nightmare.”

That’s the message Peter Thomson, the United Nations’ Special Envoy for the Ocean and and Co-Chair of Friends of Ocean Action, is sending to global leaders as they head to a crucial climate summit in November.

Detailed plans to cut greenhouse gas emissions and concrete commitments to invest in a sustainable blue economy are what’s needed to slow the decline in ocean health and put a brake on human damage to the planet, he said.

“You can’t have a healthy planet without a healthy ocean,” Thomson said. “The big emitters have to face up to the fact that they are poisoning us all. They are the ones who have to take the lead on drastically cutting their emissions.”

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Climate code red

His comments came after a major report from the UN’s Intergovernmental Panel on Climate Change confirmed ongoing changes to the ocean, including warming, more frequent marine heatwaves, acidification and reduced oxygen levels. The wide-ranging assessment of human impact on the planet said climate change is widespread, rapid and intensifying. UN Secretary General António Guterres called it a “code red for humanity.”

“The report is a huge alarm call for us all,” Thomson said. “From the ocean’s perspective, everything is connected. Think of it as one bathtub. So, what’s flowing off the Greenland ice sheet is causing a rising sea level in an atoll republic. If you’re burning coal to get your electricity, you’re contributing to the drowning of an age-old island culture.”

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Once a support for the planet as a key absorber of carbon, the ocean is now at grave risk.

Warming, acidification, deoxygenation, changing circulation patterns and rising sea levels threaten marine life and ecosystems and put at risk the future ability of the seas to indirectly support life on Earth, Thomson said.

“We can see there are going to be increasing marine heatwaves and this, along with acidification, really puts the survival of tropical coral reefs in particular into jeopardy,” he said.

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Ocean acidification, increased frequency of landslides, and possible changes to ocean currents are some of the impacts of climate change that could most affect Iceland, according to the country’s experts. Responding to the newly released report from the UN’s Intergovernmental Panel on Climate Change (IPCC), Iceland’s Environment Minister Guðmundur Ingi Guðbrandsson says government around the world need to step up their response to the climate crisis.

The PICC’s newest climate change report, intended as a resource for policymakers, compiles the latest data on climate change. Compared to the panel’s earlier reports, its findings are categorical about climate change being caused by humans and about the severity of the consequences it has in store.

Ocean acidification as concerning as warming

Tómas Jóhannesson is Director of Glaciology and an expert on the avalanche team at the Icelandic Met Office. He says the impact on the ocean surrounding Iceland is one of the biggest concerns regarding the local impact of climate change. The earth’s ocean’s have absorbed around 90% of the heat that has accumulated due to the increased greenhouse effect.

Considering Iceland’s dependence on the ocean, its acidification as a result of the carbon it absorbs from the atmosphere could be a long-term issue for the country. Acidification can affect the survival of smaller ocean organisms, in turn affecting the survival of fish and sea birds. “The acidification of the sea is unequivocal and is just as much a reason to stop emissions as warming,” Tómas stated.

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The landmark report released yesterday by the Intergovernmental Panel on Climate Change (IPCC) has left many people reeling about the current and future state of our planet. But Tamsin Edwards at King’s College London, a lead author on the report, says it is understandable that it takes time for the gravity of the situation to sink in. “I think many people aren’t that aware that we have already committed ourselves to changes that are irreversible. That is a profound thing to take on board,” she says.

Those changes include warmer ocean temperatures, ocean acidification and a decline in oxygen levels in our seas. All are now irreversible on centennial to millennial time scales because of humanity’s fossil fuel burning and other activities. “We are changing the planet. It will continue to change no matter what we do in terms of our emissions, for hundreds of thousands of years. That is beyond our comprehension in many ways,” says Edwards.

Her involvement in reviewing the global environmental crisis is intimately connected to her own personal health crisis. Edwards was appointed a lead author on the report in 2018, around the same time she was diagnosed with bowel cancer. Three years ago, she delayed chemotherapy to attend a vital meeting in China with some of the 234 other authors of the report. The covid-19 pandemic pushed those meetings online, culminating in the past fortnight where the final text was approved by 195 governments, a process that adds to the report’s gravitas.