A team of early career ocean professionals, including three OFI-supported Dalhousie PhD students, are uncovering new insights into Canada’s marine carbon sink and the unique challenges Canada faces as an ocean nation.
By synthesising carbon dioxide exchange values from various studies on surface ocean air–sea carbon dioxide exchange, the research team is attempting to improve our understanding of the marine carbon sink in Canadian national and offshore waters and the ocean's role in the global carbon cycle. The work was conducted as part of the Canada Marine Carbon Sink project.
The challenge of Canadian waters
Canada faces a challenge unlike any other – its coastline runs along Pacific, Atlantic, and Arctic waters, three of the planet’s major ocean basins. Furthermore, the physical and biological characteristics of the three oceans vary dramatically, making it difficult to consider marine systems when forming climate mitigation strategies.
Each ocean basin contains diverse oceanographic regions such as the continental shelf, and the open ocean, for example. These geographical differences, along with biological and seasonal changes, increase the variability of its carbon-storing capabilities. Specifically, the team of scientists notes that Canadian waters are a net overall carbon sink, but depending on the region and season, can act both as a carbon sink and as a carbon source.
The Canadian Arctic remains unique in the global carbon cycle as it is directly impacted by sea ice. The presence of sea ice effectively prevents ocean air–sea carbon dioxide exchange, further adding to the seasonal variability observed within these waters. Despite this, the reported carbon uptake values in these waters are some of the highest in Canada.
The Canadian Atlantic, especially in the Labrador Sea and the Baffin Bay, is important for absorbing atmospheric carbon dioxide. This is largely due to its distinctive deep-water mixing with the ability to transport carbon dioxide into the deep ocean for long-term storage. The regional variabilities are tied directly to the strength of the water column mixing – an element of ocean dynamics that could be reduced by increasing global warming.
The need to better understand the carbon sink
The global ocean’s ability to absorb carbon dioxide is an important consideration in our climate change mitigation strategies. The marine carbon sink refers to the amount of carbon the ocean can remove from the atmosphere and store within it.
A better understanding of these storage capabilities can help inform future climate and emission-related forecasting. As the team’s recent publication states , the current data suggests that about ¼ of the carbon dioxide produced by humans has been taken out of the atmosphere and into the ocean and
“It’s not surprising how big the role of the ocean is to the global carbon cycle, but very few policies in Canada consider our oceans as part of the mitigation strategies,” says Kitty Kam, a current Dalhousie PhD Oceanography student.
The variability of the ocean's carbon sink has not yet been properly accounted for since it is poorly understood. There still exist gaps in the scientific knowledge - especially in more northern regions - which limits scientists’ ability to gauge how climate-related changes will impact the processes in the carbon sink.
“There are associated biological and chemical processes taking place in the ocean that also contribute to the exchange of carbon,” says Christina Braybrook, a current University of Calgary PhD student.
The future for ocean scientists
More oceanographic observations and data-assimilated models are required to fill gaps and improve our understanding of how the sea-air carbon exchange functions over large periods of time, and how it may change with the changing climate.
There are ongoing discussions around ocean-based carbon dioxide removal strategies, which are interventions that accelerate the ocean's ability to store carbon, as potential solutions to remove more carbon from the atmosphere.
A better understanding of the ocean's process is required to ensure these efforts are successful. To accomplish this, the team suggests that monitoring and capacity-building strategies within Canada must be improved to establish a known baseline and distinguish between the ocean’s natural variability and carbon removal efforts.
“Overall, it’s tough to tell what’s happening if you’re not taking measurements and improving models before you introduce interventions,” says Patrick Duke, the lead author of this publication and a current University of Victoria PhD student.
As ocean scientists move forward, there must be a focus on improving equity, diversity, and inclusion within the ocean sciences. Indigenous voices have historically been suppressed by academic institutional barriers. Canada’s history of colonialism and systemic oppression of Indigenous peoples drives the need for ongoing truth and reconciliation.
Collaborative efforts offer opportunities for traditional knowledge sharing to bridge Western and Indigenous ways of knowing. The problems faced by climate change will require adaptation and mitigation strategies tailored to each individual community based on their specific needs.
