Award: OCE-1850723

The oceans play an essential role in the removal of carbon dioxide from the atmosphere and its storage deep in the ocean interior, which is a natural form of marine Carbon Dioxide Removal (mCDR). The uncertainty in the magnitude of this carbon removal remains high, in part because of the lack of highly time-resolved data that allows scientists to disentangle the biological, chemical and physical processes that underpin the ocean’s natural carbon removal ability. Moreover, at the Bermuda Atlantic Time-series Study site in the Sargasso Sea, the variability in the carbon removal is conflated by differences in how the ocean is sampled, whether it be biological or geochemical measurements. This project sought to tackle this problem and resolve these differences by routinely deploying ocean gliders to measure key ocean biological and geochemical variables continuously for a period longer than a year. This project presented many challenges, scientific and social, but in the end, we were able to generate a time-series record based upon the glider observations. Our glider observations supported our general understanding that the ‘spring bloom’ period is when much of the annual carbon removal from the surface ocean occurs in the Sargasso Sea through the process of production and sinking of particles containing carbon. Interestingly these results showed that much of that sinking carbon was quickly consumed and converted back to carbon dioxide within the same season. In contrast, the summer, when nutrients are depleted, that water is warmest and it is thought that there is little to no carbon removal, was actually the period when much of the carbon removal happened. This carbon removal was supported by the upward diffusion of nutrients and the slow growth of the smallest phytoplankton cells. Overall these results give us insight into how a future, nutrient-depleted and warm, ocean may function. This is important because the ocean regions that function like the Sargasso Sea, the nutrient-deplete ocean gyres, account for over half of the ocean’s total surface area. These results, and other recent work from the Sargasso Sea, suggest that biological processes in these ocean gyres may be more resilient in the face of climate change than our current generation of ocean models predict. Thus, the natural ability of the ocean for carbon dioxide removal may be maintained at some level moving into the future. Last Modified: 06/21/2023 Submitted by: Michael Lomas