Oceans are the planet’s greatest carbon sink, absorbing up to 30 per cent of the human-caused greenhouse gas emissions fuelling the climate crisis. Photo of Deepwater Horizon fire / US Coast Guard / Wikipedia
As the climate crisis gets worse, oceans — the planet’s greatest carbon sink — can no longer be overlooked.
The heat stored in the Earth’s entire atmosphere is equal to what’s stored in the top few metres of our oceans. If that wasn’t enough, oceans produce more than 50 per cent of the planet’s oxygen and regulate our climate and weather patterns.
In Canada, home of the world’s longest coastline, we can’t meet our climate and biodiversity goals without paying greater attention to the threats oceans face and the solutions they can provide. Especially as the feds doubled down on their pledge to protect 30 per cent of Canada’s waters and lands by 2030 at last month’s COP15 biodiversity summit in Montreal.
As part of a new Canada’s National Observer series breaking down climate basics, we’re diving into some common questions about how and why oceans matter to climate change.
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What is ocean acidification?
Greater amounts of CO2 in the ocean reduce the water’s pH levels, making it more acidic, along with its levels of calcium carbonate — a key building block for many creatures’ shells or skeletons, such as crabs, shellfish, prawns, corals, sea urchins and tiny marine snails, called pteropods, which fish like salmon depend on for food. Some of the initial red flags around ocean acidification surfaced in Washington state and Oregon a decade ago when shellfish hatcheries suffered massive die-offs of baby oysters.
As the ocean absorbs ever more carbon dioxide from the atmosphere, the pH level in many of its seawaters is falling. In other words, their acidity is increasing.
Ocean acidification poses an existential threat to many forms of marine life, and thus to food chains, livelihoods and economies. What is it, and what can we do to avoid its worst impacts?
Ocean acidification is a consequence of increasing carbon dioxide (CO2) emissions, a greenhouse gas driving climate change. The ocean absorbs around one third of all human induced CO2, causing a change in seawater chemistry called ocean acidification. It presents a serious threat to marine life, ecosystem health and people whose livelihoods depend on the ocean.
When CO2 dissolves in seawater, it forms carbonic acid (H2CO3), releasing hydrogen ions (H+) and increasing ocean acidity. Acidity plays a key role in many biological mechanisms, including calcification.
Calcium carbonate (CaCO3) is crucial for organisms which need calcium to develop, build and maintain their shells and skeletons, such as certain types of plankton, oysters, crabs, sea urchins, shrimps and lobsters.
Ocean acidification makes it harder for them to maintain these calcified structures. This can cause disruptions within food chains.
Lilliehook Glacier in Svalbard Bay, in the Svalbard archipelago in the Arctic Ocean. COURTESY HSH PRINCE ALBERT II OF MONACO
In 2005, I stood in front of the Lilliehook Glacier in Svalbard Bay, in the Svalbard archipelago in the Arctic Ocean; the same location my great-great-grandfather explored 100 years prior. The integrity of glaciers and ice caps I observed, compared to his photographs, presented the reality that a climate crisis was coming sooner than most believed and inspired my decision that the polar regions would become a priority for the foundation I founded in 2006, the Prince Albert II of Monaco Foundation.
While my expedition to the South Pole in 2009 emphasized the need to accelerate global action, my latest visit to the Arctic in June confirmed that the world community has not been paying enough attention to these remote areas and is not fully cognizant of the changes they are experiencing that will impact all nations worldwide.
What happens in the polar regions doesn’t stay in the polar regions. It strikes the entire planet, knocking down our doors with dire consequences: rising sea levels; increased frequency and intensity of extreme weather events; catastrophic droughts and floods; accelerating ocean acidification; disruption of ecosystems; and loss of biodiversity.
Ocean waves break onto a beach not far from Breidamerkurjokull glacier on Aug. 18, 2021 near Hof, Iceland. Iceland is undergoing a strong impact from global warming, as are the waters that surround it. Sean Gallup—Getty Images
In the battle to reduce the amount of carbon dioxide in the atmosphere and slow global warming, humans have a few natural allies. The best-known of these allies are trees, those charismatic carbon sinks that create shade and oxygen for us and our fellow landbound creatures. But land covers less than a third of the earth, and trees live on a shrinking sliver of that. The ocean covers most of the rest of the planet and absorbs up to 50% of all fossil fuel-related carbon dioxide emissions—20 times more than trees, other land plants, and soil combined.
“All the plans moving forward for stabilizing earth’s climate depend on the ocean continuing to remove carbon dioxide from the atmosphere,” says Scott Doney, a University of Virginia professor who researches how ocean ecology and the carbon cycle responds to climate change. “It’s a really important stabilizer of the planetary climate.”
The ocean’s ability to absorb carbon and stabilize the climate is attracting attention from scientists and companies alike looking for ways to counteract the rise of anthropogenic greenhouse gas emissions. Within this, the world of blue carbon offsets is gaining popularity. Companies can buy and sell these credits, which represent a certain amount of emissions being removed from the atmosphere and absorbed by the ocean. It’s easier said than done, though. Some blue carbon projects, especially those that involve geoengineering, have been criticized for a lack of data on efficacy and consequences. But there’s no doubt that the ocean has an outsized influence on the climate, and no one working to fight global warming should turn their back on the sea.
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The ocean’s impact on the climate goes beyond its role as a carbon sink. It also serves as a heat sink due to the same conveyor-belt currents that send dissolved inorganic carbon to the depths. These currents carry warm, salty water from the equator up to the North Atlantic, where it cools and sinks due to its salt-saturated density, bringing the heat with it. About 90% of the planet’s heat is stored in the ocean.
Here’s the downer: Fossil fuel emissions and other anthropogenic effects are having a negative effect on all of the ocean’s mechanisms for absorbing carbon and heat. Carbon dioxide is more soluble in cold water, so global warming is slowing down the physical pump. The amount of carbon in the atmosphere makes it harder for water to cool down because of the greenhouse effect (carbon dioxide blocks the waves of thermal radiation that the ocean sends back out to space after being heated by the sun). These temperature changes are also shifting the long-established currents of the ocean, which is changing both global weather patterns (ocean circulation is interlinked with atmospheric circulation) and the path carbon traditionally takes toward the ocean floor.
And because carbon dioxide reacts with water to form carbonic acid, the ocean grows more acidic as it absorbs more carbon—a process known as ocean acidification. This has its own negative effects on marine ecosystems and may affect the growth of the photosynthetic plankton that form the basis of the biological pump. A 2015 study found that ocean acidification will cause several species of phytoplankton to die out.
The natural resources that form ocean ecosystems can play a significant role in the socio-economic growth and development of nations.
West Africa has a variety of marine and coastal ecosystems, found within the Atlantic Ocean. This is one of the most diverse and economically important fishing zones in the world and provides an income for many through fishing, shipping, logistics and mining.
But unregulated and unsustainable exploitation has degraded the ecosystems severely. Threats have come from land based sources of pollution, insecurity and piracy, illegal and harmful fishing practices, and climate change.
These multiple stressors have had a negative impact on the ecological integrity and health of West Africa. They are causing an alarming decline in fishery resources, loss of coral reefs and seashells, coastal erosion, ocean acidity and rising sea levels.
Since the beginning of the Industrial Revolution, when humans began burning coal in large quantities, the world’s ocean water has gradually become more acidic. Like global warming, this phenomenon, which is known as ocean acidification, is a direct consequence of increasing levels of carbon dioxide (CO2) in Earth’s atmosphere.
In the 200-plus years since the industrial revolution began, the concentration of carbon dioxide (CO2) in the atmosphere has increased due to human actions. During this time, the pH of surface ocean waters has fallen by 0.1 pH units. This might not sound like much, but the pH scale is logarithmic, so this change represents approximately a 30 percent increase in acidity.
The oceans have absorbed between 24% and 33% of anthropogenic carbon dioxide (CO2) emissions during the past five decades. While this uptake provides a valuable service to human societies by moderating the rate and severity of climate change, it comes at a cost for the oceans. The massive input of CO2 generates sweeping changes in the chemistry of seawater, especially on the carbonate system. These changes are collectively referred to as “ocean acidification” because increased CO2 lowers seawater pH (i.e. increases its acidity).
IUCN – International Union for Conservation of Nature.Resource.
Anthropogenic CO2 emissions directly affect atmospheric chemistry but also have a strong influence on the oceans. Gattuso et al., review how the physics, chemistry, and ecology of the oceans might be affected based on two CO2 emission trajectories: one business as usual and one with aggressive reductions…
Atmospheric carbon dioxide concentration is expected to exceed 500 parts per million and global temperatures to rise by at least 2 degrees C by 2050 to 2100, values that significantly exceed those of at least the past 420,000 years during which most extant marine organisms evolved…
Ocean acidification may have severe consequences for marine ecosystems; however, assessing its future impact is difficult because laboratory experiments and field observations are limited by their reduced ecologic complexity and sample period, respectively.
…Ocean observations are severely limited with respect to providing reliable estimates of the signal-to-noise ratio of human-induced trends in carbonate chemistry against natural factors. Using three Earth system models we show that the current anthropogenic trend in ocean acidification already exceeds the level of natural variability by up to 30 times on regional scales…
…By performing a partial-equilibrium analysis, we estimate global and regional economic costs of production loss of mollusks due to ocean acidification. Our results show that the costs for the world as a whole could be over 100 billion USD with an assumption of increasing demand of mollusks with expected income growths combined with a business-as-usual emission trend towards the year 2100…
The ocean is becoming more acidic worldwide as a result of increased atmospheric carbon dioxide (CO2) and other pollutants. This fundamental change is likely to have substantial ecological and economic consequences globally. In this Article, we provide a toolbox for understanding and addressing the drivers of an acidifying ocean.
Es asombroso pensar que hace sólo diez años casi nadie había oído hablar de la acidificación
del océano. Ahora es mucho más ampliamente comprendido que la creciente cantidad
de dióxido de carbono (CO2) que emitimos en el aire por nuestras actividades está
reaccionando con el océano alterando su química, recorriéndolo a lo largo de la escala hacia
la acidez y, entre otros efectos, reduciendo la disponibilidad de iones de carbonato que
necesitan muchos animales marinos y plantas para construir sus conchas y esqueletos…
Atmospheric carbon dioxide (CO2) concentration has increased by 42% since the onset of the industrial revolution due to emissions from fossil fuel burning, cement production and land-use change…
Resource type: website
Resource format: webpage
WMO – World Meteorological Organization, 7 July 1905. Resource.
In order to unpack such complexity, the WMO State of the Global Climate uses seven Climate Indicators to describe the changing climate providing a broad view of the climate at a global scale. They are used to monitor the domains most relevant to climate change, including the composition of the atmosphere, the energy changes that arise from the accumulation of greenhouse gases and other factors, as well as the responses of land, oceans and ice. The following site aims to provide an overview of the annually produced State of the Climate report.
Resource type: report
Resource format: webpage
WMO – World Metereological Organization, 1 April 2021. Resource.
The on-going rise of carbon dioxide (CO2) in the atmosphere is not only changing our climate; it is also changing our oceans. More than a quarter of the CO2 released to the air by human activities is absorbed by the world’s oceans.
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