Global Warming Increases Interannual and Multidecadal Variability of Subarctic Atlantic Nutrients and Biological Production in the CESM1‐LE

Abstract

Abstract Earth system models indicate that the Subarctic Atlantic Ocean ecosystems are uniquely sensitive to global warming. Nutrients, phytoplankton biomass, and phytoplankton production all decline precipitously in global warming scenarios. Superimposed on this forced response is changing internal variability that is not fully understood. Here, a large ensemble of simulations with the Community Earth System Model is used to quantify how global warming affects the interannual and multidecadal variability of phytoplankton production integrated over the Subarctic Atlantic. Surprisingly, it is found that this variability increases non‐monotonically with global warming. The increased variability of production is caused by an elevated volatility of wintertime surface nutrient concentrations, which is a consequence of a rising sensitivity of these nutrients to winter mixing and overturning fluctuations, which overcomes a reduced amplitude of these physical fluctuations with warming. Future work is needed to fully understand how internal climate variability impacts ocean ecosystems in a warming climate.