03 April 2018

Sustained Climate Warming Drives Declining Marine Biological Productivity

Nutrients increasingly transferred to the deep ocean with strong climate warming, driven by changes in the Southern Ocean around Antarctica.

Science

Researchers from the University of California Irvine, with collaborators from Oak Ridge National Laboratory, the National Center for Atmospheric Research, the University of Virginia and Cornell University, examined the impacts of sustained climate warming on the oceans following the Representative Concentration Pathway 8.5 (RCP8.5) and its extension to the year 2300, in an Earth system model simulation. Upper ocean nutrient concentrations decline globally, reducing biological productivity as the nutrients that support marine ecosystems are increasingly transferred to the deep ocean.

Impact

Our analysis suggests that sustained multi-century climate warming could drive a net transfer of nutrients to the deep ocean, depressing global-scale marine productivity. We estimate that the reductions in plankton productivity in our simulation would reduce the global fishery yield 20% by 2300, with reductions of nearly 60% in the North Atlantic.

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, where upwelling brings deep waters up to the surface. These nutrient-rich waters drift northwards, eventually subducting to form Subantarctic Mode and Antarctic Intermediate waters at mid-depths. The nutrients transported northwards in these waters fuel much of the biological productivity in the oceans. With sustained, multi-century climate warming, shifting winds, warming surface waters, and melting sea ice drive increased biological production around Antarctica, leading to local trapping of nutrients, and reductions in the northward lateral transport of nutrients that fuels marine ecosystems worldwide. This drives a net transfer of nutrients to the deep ocean, and depletion of nutrients in the upper ocean, which depresses marine biological productivity at the global scale.

Contact
J. Keith Moore
University of California at Irvine (UC Irvine)
Publications
Moore, JK, W Fu, F Primeau, GL Britten, K Lindsay, M Long, SC Doney, N Mahowald, FM Hoffman, and J Randerson.  2018.  "Sustained Climate Warming Drives Declining Marine Biological Productivity."  Science 359(6380): 1139-1143.  https://doi.org/10.1126/science.aao6379.