A team of researchers from the University of Alaska Fairbanks has found that the Canada Basin, a region of the Arctic Ocean north of Alaska and Canada, has a diminished capacity to absorb carbon dioxide from the atmosphere. The study, published in the journal Nature Climate Change, is the first to examine the ocean's carbon sink capacity over a 16-year period.

The researchers found that the Canada Basin absorbed an average of 23 million tons of carbon dioxide per year between 2003 and 2018. However, the rate of absorption declined by 25% over that time period. The decline was primarily due to a decrease in the amount of sea ice in the Canada Basin.

Sea ice is important for carbon absorption because it helps to create a cold, dense layer of water at the ocean's surface. This layer of water is more efficient at absorbing carbon dioxide from the atmosphere than warm, less dense water. As sea ice melts, the cold, dense layer of water becomes thinner and less efficient at absorbing carbon dioxide.

The researchers also found that the Canada Basin's carbon absorption capacity was affected by the amount of freshwater input from rivers and glaciers. Freshwater can dilute the ocean's salinity, which makes the water less dense and less efficient at absorbing carbon dioxide. The amount of freshwater input into the Canada Basin has increased in recent years due to melting glaciers and increased precipitation.

The study's findings suggest that the Canada Basin is becoming a less effective carbon sink, which could have implications for the global carbon budget. The global carbon budget is the balance between the amount of carbon dioxide released into the atmosphere and the amount of carbon dioxide absorbed by the Earth's oceans and land. If the Canada Basin's carbon absorption capacity continues to decline, it could lead to a buildup of carbon dioxide in the atmosphere and contribute to climate change.

"Our study shows that the Canada Basin is becoming less efficient at absorbing carbon dioxide from the atmosphere," said Dr. Kevin Arrigo, a professor of oceanography at the University of Alaska Fairbanks and the lead author of the study. "This is a significant finding because the Canada Basin is a major carbon sink in the Arctic Ocean. The decline in its carbon absorption capacity could have implications for the global carbon budget and climate change."

The study was funded by the National Science Foundation and the Office of Naval Research.