Decrease in the CO₂ Uptake Capacity in an Ice-Free Arctic Ocean Basin

It has been predicted that the Arctic Ocean will sequester much greater amounts of carbon dioxide (CO₂) from the atmosphere as a result of sea ice melt and increasing primary productivity. However, this prediction was made on the basis of observations from either highly productive ocean margins or ice-covered basins before the recent major ice retreat. We report here a high-resolution survey of sea-surface CO₂ concentration across the Canada Basin, showing a great increase relative to earlier observations. Rapid CO₂ invasion from the atmosphere and low biological CO₂ drawdown are the main causes for the higher CO₂, which also acts as a barrier to further CO₂ invasion. Contrary to the current view, we predict that the Arctic Ocean basin will not become a large atmospheric CO₂ sink under ice-free conditions.