Starving the Oceans

The Science

Researchers examined the impacts of sustained climate warming on the oceans. In an Earth system model simulation, they examined how the oceans would change through the year 2300 with continued strong warming conditions. They found that upper ocean nutrient concentrations declined globally. The nutrients that support phytoplankton and marine ecosystems are increasingly transferred to the deep ocean.

The Impact

Sustained multi-century climate warming could drive a net transfer of nutrients to the deep ocean. This transfer affects the global fishery yield and other organisms near the ocean surface. Fishery yields could drop by 20 percent globally by 2300; the North Atlantic Ocean could see fishery yields drop by nearly 60 percent.

Summary

The primary pathway for nutrient-rich, deep ocean waters to return to the surface is in the Southern Ocean surrounding Antarctica, at the Antarctic Divergence. Here, upwelling brings deep waters up to the surface. These nutrient-rich waters drift northwards, eventually subducting to form sub-Antarctic Mode and Antarctic Intermediate waters at mid-depths. The nutrients transported northwards in these waters feed much of the biological productivity, or life in the oceans. With sustained, multi-century climate warming, researchers found that shifting winds, warming surface waters, and melting sea ice drive increased biological production around Antarctica. This leads to local trapping of nutrients and reductions in the northward lateral transport of nutrients that fuel marine ecosystems worldwide. This drives 1) a net transfer of nutrients to the deep ocean and 2) depletion of depletes nutrients in the upper ocean, which depresses marine biological productivity at the global scale.

Funding

This research was performed for the Reducing Uncertainties in Biogeochemical Interactions through Synthesis and Computation Scientific Focus Area, which is sponsored by the Earth and Environmental System Modeling Program (EESM), under the Regional and Global Climate Model Analysis activity. Additional support came from projects sponsored by the EESM Earth System Modeling (ESM) activity. EESM is part of the Climate and Environmental Sciences Division of Biological and Environmental Research in the Department of Energy Office of Science.

Publications

J.K. Moore, W. Fu, F. Primeau, G.L. Britten, K. Lindsay, M. Long, S.C. Doney, N. Mahowald, F.M. Hoffman, and J.T. Randerson, “Sustained climate warming drives declining marine biological productivity.” Science 359, 1139 (2018). [DOI: 10.1126/science.aao6379]