Diazotrophy as a key driver of the response of marine net primary productivity to climate change

Abstract. The impact of anthropogenic climate change on marine net primary production (NPP) is a reason for concern because changing NPP will have widespread consequences ecosystems and their associated services. Projections by the current generation Earth system models suggested decreases in global response to future change, albeit with very large uncertainties. Here, we make use two versions Institut Pierre-Simon Laplace Climate Model (IPSL-CM) that simulate divergent responses similar high-emission scenarios 21st century identify nitrogen fixation as main driver these responses. Differences way N parameterised biogeochemical component PISCES (Pelagic Interactions Scheme Carbon Ecosystem Studies) IPSL-CM lead N-fixation rates are either stable or double over course century, resulting decreasing increasing NPP, respectively. An evaluation model does not help constrain projection However, more comprehensive version PISCES, variable nitrogen-to-phosphorus ratios well revised parameterisation temperature sensitivity fixation, suggests only moderate changes globally averaged century. This leads line model-mean recent multi-model intercomparison. Lastly, despite contrasting trends all our significant reductions planktonic biomass. projected plankton biomass may be robust indicator than potential across models.