ScienceDaily (Apr. 10, 2009) — The North Atlantic Ocean is one of the Earth’s tools to offset natural carbon dioxide emissions. In fact, the ‘carbon sink’ in the North Atlantic is the primary gate for carbon dioxide (CO₂) entering the global ocean and stores it for about 1500 years. The oceans have removed nearly 30 per cent of anthropogenic (man-made) emissions over the last 250 years. However, several recent studies show a dramatic decline in the North Atlantic Ocean's carbon sink.

Concerned by this decline, a group of international scientists, including Helmuth Thomas, professor of oceanography at Dalhousie University, spent the last two years investigating the world’s largest carbon sink. They weren’t sure what was causing the decrease, whether it was man-made or natural reasons.

“There were massive changes in the coastal carbon cycle, and it was similar throughout the ocean,” says Dr. Thomas, who wrote about the study in Global Biogeochemical Cycles. 

Recent observational studies found that the North Atlantic carbon uptake has decreased by 50 per cent over the last ten years. While many are quick to blame anthropogenic climate change, Dr. Thomas and his colleagues found different results. 

They believe the decrease is a natural phenomenon as a result of the North Atlantic Oscillation (NAO), which causes weather patterns to change. “The next phase should once again increase in carbon uptake,” says Dr. Thomas. These natural phenomenons have the potential to mask the effects of anthropogenic climate change.

These findings are crucial in understanding how this natural system is reacting to climate change and dealing with increased man-made carbon emissions. Dr. Thomas says more research must be done; including enhanced observational efforts and developing models for analysis to fully understand the long-term effects, such as how the oceanic sink will deal with increased carbon emissions from humans. However, he hopes the study, reported on in the March edition of Nature, will help all climate change scientists with their research. 

“This research is the foundation for research in ocean acidification which has implications on marine life and corals,” explains Dr. Thomas.

He also cautions against misinterpreting the findings. “There are natural systems that deal with and react to natural climate change. We have to understand these to assess how anthropogenic climate change is affecting them.”

Journal references:

1. Gruber et al. Carbon cycle: Fickle trends in the ocean. Nature, 2009; 458 (7235): 155 DOI: 10.1038/458155a
2. Thomas et al. Changes in the North Atlantic Oscillation influence CO₂ uptake in the North Atlantic over the past 2 decades. Global Biogeochemical Cycles, 2008; 22 (4): GB4027 DOI: 10.1029/2007GB003167

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