A challenge as big as the
Assessing the sea for its ability to sequester carbon
Katja Fennel
If the processes that keep CO2 in the ocean change even in a subtle way, even a small change in the carbon inventory of the ocean would mean a huge change in the atmosphere. We need to understand it. It’s crucially important.
Department Chair, Oceanography
Dalhousie University

Transforming climate action

The Earth is teetering toward climate crisis. The ocean, more than anything, is helping to keep the balance. But emerging science shows the ocean’s ability to absorb carbon and regulate temperatures is changing in ways we don’t understand. It is a change that is not accounted for in global climate targets. It’s a risk we can no longer afford to take. The time has come to transform climate action.

Katja Fennel

Dalhousie Oceanographer Dr. Katja Fennel is trying to get a handle on how the ocean is changing in its ability to cycle carbon and oxygen, because life below and above the water depends on it. 

“The ocean is a hugely important sink for carbon,” says Dr. Fennel. “It really has mitigated global warming by taking up a lot of the fossil fuel carbon that we put into the atmosphere. But it’s not always going to continue to take it up at the same rate.”

To get the data she needs, she relies on readings beamed up to satellites by close to 4,000 submergible Argo floats that dot the ocean from the South Atlantic to the North Pacific and everywhere in between. Initially launched 20 years ago, the fleet of floats drift on ocean currents and dive to depths of up to 2,000 meters to provide feedback on how the ocean is moving and its chemical constituents.

Circulation diagram

Out of circulation

Dr. Fennel is focused on readings from a new set of floats released in the last two years. The floats are equipped with biogeochemical sensors that provide real time data on the presence of plankton biomass, nitrate, and oxygen in the water and how it is, or isn’t, circulating.

The fear is that global warming is causing the ocean to become increasingly stratified—a serious problem because this means the nutrients from the bottom of the ocean that feed the microscopic plant-like phytoplankton aren’t circulating there.

Slight declines, dire consequences

Dr. Fennel says phytoplankton are the basis of the marine food web. They soak up carbon dioxide from the atmosphere and act as a vehicle to cycle the gas to the deep ocean where it is sequestered for centuries to millennia. She says that even a slight decline in the ocean’s microscopic plant life may have dire consequences for ocean life and climate change. 

“We have to get a handle on what the ocean’s carbon inventory is, how it is changing, because the ocean holds 50 times more CO2 than the atmosphere,” she says. “If the processes in the ocean that keep the CO2 in there change even in a subtle way, even a small change in the carbon inventory of the ocean would mean a huge change in the atmosphere. We need to understand it. It’s crucially important.”

Katja Fennel

An ocean-first approach

Transforming Climate Action will bring together more than 170 researchers at Dalhousie and its academic partners to embark on the most intensive investigation into the ocean’s role in climate change ever undertaken. It will make Canada a global leader in climate science, innovation, and solutions by putting the ocean front and centre in the fight against a warming planet.

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