For many years scientists have operated on the belief—backed by extensive calculations and climate models—that the global ocean absorbs approximately 30% of the atmospheric carbon dioxide (CO2) produced by human activities. However, in a recent paper published in the journal Biogeosciences, Dr. Nicholas Bates, Senior Scientist and Associate Director of Research at the Bermuda Institute of Ocean Sciences (BIOS), discovered this might not always be true.
Using data collected from the ocean around Bermuda as part of the Bermuda Atlantic Time-series Study (BATS), Dr. Bates found that a mass of water called the “subtropical mode water” (or SMTW) impacts how much CO2 can be absorbed by the water in the North Atlantic Ocean. The extent and volume of this water mass is controlled, in part, by climate phenomena; specifically, the North Atlantic Oscillation (NAO).
According to Dr. Bates, “the NAO is the dominant climate mode that influences variability in the North Atlantic Ocean,” impacting the strength and frequency of the region’s winter storms, as well as the north/south shift of the Gulf Stream.
As a result, the NAO has a direct effect on how much CO2 is absorbed by the dominant upper-ocean water mass—the SMTW—in the North Atlantic Ocean. If the North Atlantic Ocean isn’t absorbing as much CO2 during certain phases of the NAO, it means that more CO2 is staying in the atmosphere and contributing to global climate change. Summarizing his findings, Dr. Bates remarked that, “natural climate variability such as NAO has a significant influence on CO2 sinks in the North Atlantic Ocean.”