August 27, 2026
The Ocean Is Earth’s Largest Carbon Sink. Here’s Why It Matters
Estimated reading time: 0 minutes
BY: Meghan Dubeau
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If it feels like summer has been hotter than ever and weather patterns more extreme, you’re not imagining it. Climate change is driving greater instability in the systems that shape our weather. It’s contributing to more intense heat waves, heavier rainfall, stronger storms, floods, droughts, and wildfires. The ocean carbon sink is one of our biggest allies in the fight against climate change. You might already know that the ocean provides us with food, supports our economy, and holds habitat for marine life. But did you know that it plays a vital role in regulating the Earth’s climate?
The ocean is our planet’s largest active carbon sink. Here’s what that means, why it’s so important, and how we can ensure that the ocean supports us for generations to come.
What is a Carbon Sink?
Forests, wetlands, soils, mycelium networks, and the ocean all act as major natural carbon sinks. But what does that mean? Carbon sinks are environments that absorb carbon, store it and help prevent it from being released back into the atmosphere. Through different processes, carbon sinks help mitigate climate change and regulate the Earth’s temperature. Trees, plants, and seaweed absorb carbon dioxide through photosynthesis; soils store carbon from dead plants and animals as they decompose. Together, these processes are part of the carbon cycle, which moves carbon between the atmosphere, ocean, soil, and living organisms.
Why the Ocean is Earth’s Largest Carbon Sink
The ocean is massive, covering about 70% of our planet. Its vast size is one of the reasons that ocean and climate change are so closely connected: it can absorb and store large amounts of carbon over longer periods. Since the beginning of the industrial era, the ocean has absorbed 25 to 30% of carbon dioxide emissions produced by human activities. This process is known as carbon sequestration.
Carbon dioxide is a greenhouse gas — a gas that traps heat in the atmosphere and contributes to the greenhouse effect. When the ocean absorbs excess carbon dioxide, it reduces how much remains in the atmosphere, helping to slow the pace of warming. The ocean also absorbs heat; roughly 90% of the excess heat caused by greenhouse gas emissions. Marine plants, plankton, seagrass, salt marshes, and deep-sea processes all help to store carbon, regulate the Earth’s temperature, and mitigate the effects of climate change as a result.
How the Ocean Stores Carbon
The ocean carbon sink works in a few different ways. Some carbon stays near the ocean’s surface briefly, while some sinks into deeper waters staying for decades, centuries, or longer. There are three main types of carbon sequestration processes.
In physical or mechanical carbon storage, carbon dioxide dissolves directly into seawater.
Biological carbon cycling is a process that begins with microscopic organisms called phytoplankton. They absorb carbon and process it through photosynthesis as they grow. Phytoplankton then become part of the food web and are eaten by other marine life that shed tissue, excrete waste, and die. All this contributes carbon-rich material back into the water where it sinks to the deepest parts of the ocean.
Coastal ecosystems, or blue carbon habitats, are places like seagrass meadows, salt marshes, and mangroves that store carbon in the plants that grow there. Their dense root systems are in water which creates the perfect conditions to slow down the decomposition process. This helps bury carbon deeper into the ground beneath, making this method more effective than land-based forests.
Why a Healthy Ocean Matters for Climate Change
Although the ocean acts as a powerful storage system, there are many risks. When carbon dioxide dissolves into seawater, it changes ocean chemistry, making seawater more acidic. Ocean acidification can make it harder for animals like corals, snails, shellfish, and other molluscs to build and maintain shells and skeletons. If conditions become too acidic, those structures can weaken or dissolve. These changes can alter marine food webs and degrade ecosystems, reducing their ability to continue storing carbon effectively. Plastic pollution, destructive fishing practices, and habitat and biodiversity loss all contribute to weakening ocean health.
The ocean mitigates the effects of climate change. It absorbs carbon emissions, regulates the Earth’s temperature, and supports all life on this planet. It is one of our greatest allies, and keeping the ocean resilient is essential for climate stability and our survival.
The better the ocean’s sequestering ability, the more support it can provide in tackling the climate crisis.
Protecting the Ocean Carbon Sink Protects Us
From preserving habitats and reducing plastic pollution, to protecting endangered species, rebuilding fish populations and managing fisheries responsibly, all these initiatives support ocean health and help safeguard biodiversity. If you’re curious about how you can help keep oceans resilient, here are a few impactful ways to take action:
Protecting habitats and endangered species, reducing plastic pollution, rebuilding fish populations, and managing fisheries responsibly, all support ocean health and help safeguard biodiversity. If you’re curious about how you can help keep oceans resilient, here are a few impactful ways to take action:
- Support marine protections and science-based ocean policies.
- Reduce single-use plastics and support reuse systems.
- Choose sustainable seafood where possible.
- Stay informed and share ocean-climate information.
- Support Oceana Canada’s campaigns to protect and restore ocean abundance.
Everything on this planet can heal, including the ocean, when we give it the chance. If we want the ocean carbon sink to continue protecting us, we need to protect it as well.
If it feels like summer has been hotter than ever and weather patterns more extreme, you’re not imagining it. Climate change is driving greater instability in the systems that shape our weather. It’s contributing to more intense heat waves, heavier rainfall, stronger storms, floods, droughts, and wildfires. The ocean carbon sink is one of our biggest allies in the fight against climate change. You might already know that the ocean provides us with food, supports our economy, and holds habitat for marine life. But did you know that it plays a vital role in regulating the Earth’s climate?
The ocean is our planet’s largest active carbon sink. Here’s what that means, why it’s so important, and how we can ensure that the ocean supports us for generations to come.
What is a Carbon Sink?
Forests, wetlands, soils, mycelium networks, and the ocean all act as major natural carbon sinks. But what does that mean? Carbon sinks are environments that absorb carbon, store it and help prevent it from being released back into the atmosphere. Through different processes, carbon sinks help mitigate climate change and regulate the Earth’s temperature. Trees, plants, and seaweed absorb carbon dioxide through photosynthesis; soils store carbon from dead plants and animals as they decompose. Together, these processes are part of the carbon cycle, which moves carbon between the atmosphere, ocean, soil, and living organisms.
Why the Ocean is Earth’s Largest Carbon Sink
The ocean is massive, covering about 70% of our planet. Its vast size is one of the reasons that ocean and climate change are so closely connected: it can absorb and store large amounts of carbon over longer periods. Since the beginning of the industrial era, the ocean has absorbed 25 to 30% of carbon dioxide emissions produced by human activities. This process is known as carbon sequestration.
Carbon dioxide is a greenhouse gas — a gas that traps heat in the atmosphere and contributes to the greenhouse effect. When the ocean absorbs excess carbon dioxide, it reduces how much remains in the atmosphere, helping to slow the pace of warming. The ocean also absorbs heat; roughly 90% of the excess heat caused by greenhouse gas emissions. Marine plants, plankton, seagrass, salt marshes, and deep-sea processes all help to store carbon, regulate the Earth’s temperature, and mitigate the effects of climate change as a result.
How the Ocean Stores Carbon
The ocean carbon sink works in a few different ways. Some carbon stays near the ocean’s surface briefly, while some sinks into deeper waters staying for decades, centuries, or longer. There are three main types of carbon sequestration processes.
In physical or mechanical carbon storage, carbon dioxide dissolves directly into seawater.
Biological carbon cycling is a process that begins with microscopic organisms called phytoplankton. They absorb carbon and process it through photosynthesis as they grow. Phytoplankton then become part of the food web and are eaten by other marine life that shed tissue, excrete waste, and die. All this contributes carbon-rich material back into the water where it sinks to the deepest parts of the ocean.
Coastal ecosystems, or blue carbon habitats, are places like seagrass meadows, salt marshes, and mangroves that store carbon in the plants that grow there. Their dense root systems are in water which creates the perfect conditions to slow down the decomposition process. This helps bury carbon deeper into the ground beneath, making this method more effective than land-based forests.
Why a Healthy Ocean Matters for Climate Change
Although the ocean acts as a powerful storage system, there are many risks. When carbon dioxide dissolves into seawater, it changes ocean chemistry, making seawater more acidic. Ocean acidification can make it harder for animals like corals, snails, shellfish, and other molluscs to build and maintain shells and skeletons. If conditions become too acidic, those structures can weaken or dissolve. These changes can alter marine food webs and degrade ecosystems, reducing their ability to continue storing carbon effectively. Plastic pollution, destructive fishing practices, and habitat and biodiversity loss all contribute to weakening ocean health.
The ocean mitigates the effects of climate change. It absorbs carbon emissions, regulates the Earth’s temperature, and supports all life on this planet. It is one of our greatest allies, and keeping the ocean resilient is essential for climate stability and our survival.
The better the ocean’s sequestering ability, the more support it can provide in tackling the climate crisis.
Protecting the Ocean Carbon Sink Protects Us
From preserving habitats and reducing plastic pollution, to protecting endangered species, rebuilding fish populations and managing fisheries responsibly, all these initiatives support ocean health and help safeguard biodiversity. If you’re curious about how you can help keep oceans resilient, here are a few impactful ways to take action:
Protecting habitats and endangered species, reducing plastic pollution, rebuilding fish populations, and managing fisheries responsibly, all support ocean health and help safeguard biodiversity. If you’re curious about how you can help keep oceans resilient, here are a few impactful ways to take action:
- Support marine protections and science-based ocean policies.
- Reduce single-use plastics and support reuse systems.
- Choose sustainable seafood where possible.
- Stay informed and share ocean-climate information.
- Support Oceana Canada’s campaigns to protect and restore ocean abundance.
Everything on this planet can heal, including the ocean, when we give it the chance. If we want the ocean carbon sink to continue protecting us, we need to protect it as well.
