Canada’s Oceans Now: Arctic Ecosystems 2023 - Source or sink: CO₂ in Arctic waters

Source or sink: CO₂ in Arctic waters
Limited data shows that Canadian Arctic waters are a sink for CO₂ – but not all the time. We need more information to understand the full picture

This infographic takes the form of a simplified arctic ocean landscape, comprised of open water, sea ice, and a river. A yellow text box on the top left contains explanatory text stating “when the ocean absorbs CO₂ from the atmosphere, we called it a CO₂ sink; when it releases CO₂ into the atmosphere, it is a CO₂ source. Within the landscape different carbon dioxide (CO₂) sources (orange upward arrow) and sinks (dark blue downward arrow) are shown and explained through text scattered around the infographic:

• Next to red arrows indication the flow of CO₂ from under the broken ice to the atmosphere: “Trapped CO₂ release: CO₂ trapped under the ice can be quickly released when ice starts to melt or break up, creating a short-term CO₂ source.”
• Next to broken ice shapes and a blue arrow representing water from ice melt: “Melting ice: Meltwater floats on top of saltier water and absorbs more CO₂ (sink).”
• On a green area representing phytoplankton in the surface ocean water: “Phytoplankton: Phytoplankton need CO₂ to grow. When they bloom during the open-water period, they create a CO₂ sink.”
• Next to swirls and an arrow representing ocean water movement: “Water movement: mixing can alter the direction and strength of CO₂ exchange.”
• Next to a horizon with an orange sun that has three arrows representing spring (blue/down), summer (red/up) and fall (blue/down). “Seasonal switches: Hudson Bay switches from a sink to a CO₂ source in late summer and then back to a sink in the fall.”
• Next to an illustration of water flowing into the ocean from land with two red arrows indicating CO₂ moving from the ocean to the atmosphere: “River water: rivers carry decomposing materials which gives off CO₂ as it breaks down. This can make river water at the surface of the ocean a source of CO₂.”

On the bottom left, a text box explains how CO₂ changes with depth, stating:

• “CO₂ at the surface of the ocean can be very different from waters just a few meters below. We need measurements from multiple depths to fully understand CO₂ exchange in the ocean.”

On the bottom right, a map of the Canadian Arctic shows circular markers with downwards dark blue triangles. The number associated with each circle indicates the amount of CO₂ absorbed by the ocean at that location in an entire year.  The units are mol C m^-2 year^-1. All values on the map indicate a sink of CO₂ and values range from 0.5 to 3.7, but these are approximate and can vary over time.