Date of Original Version
Global observations show that the ocean lost approximately 2% of its oxygen inventory over the past five decades1,2,3, with important implications for marine ecosystems4,5. The rate of change varies regionally, with northwest Atlantic coastal waters showing a long-term drop6,7 that vastly outpaces the global and North Atlantic basin mean deoxygenation rates5,8. However, past work has been unable to differentiate the role of large-scale climate forcing from that of local processes. Here, we use hydrographic evidence to show that a Labrador Current retreat is playing a key role in the deoxygenation on the northwest Atlantic shelf. A high-resolution global coupled climate–biogeochemistry model9 reproduces the observed decline of saturation oxygen concentrations in the region, driven by a retreat of the equatorward-flowing Labrador Current and an associated shift towards more oxygen-poor subtropical waters on the shelf. The dynamical changes underlying the shift in shelf water properties are correlated with a slowdown in the simulated Atlantic Meridional Overturning Circulation (AMOC)10. Our results provide strong evidence that a major, centennial-scale change of the Labrador Current is underway, and highlight the potential for ocean dynamics to impact coastal deoxygenation over the coming century.
Claret, M., Galbraith, E. D., Palter, J. B., Bianchi, D., Fennel, K., Gilbert, D., & Dunne, J. P. (2018). Rapid coastal deoxygenation due to ocean circulation shift in the northwest Atlantic. Nature Climate Change, 8, 868-872. doi: 10.1038/s41558-018-0263-1
Available at: http://dx.doi.org/10.1038/s41558-018-0263-1