Decline in Atlantic Primary Production Accelerated by Greenland Ice Sheet Melt

Projections of climate impacts on marine net primary production (NPP) are reliant on Earth System Models (ESMs) that do not contain dynamic ice sheets. We assess the impact of potential Greenland ice sheet meltwater on projections of 21st century NPP using idealized ESM simulations. Under an extreme melt scenario, corresponding to 21st century sea level rise close to 2 m, Greenland meltwater amplified the decline in global NPP from a decrease of 3.2 PgC/yr to a decrease of 4.5 PgC/yr, relative to present. This additional reduction in NPP predominately occurs in the North Atlantic subtropical and subpolar gyres, as well as Atlantic eastern boundary upwelling systems. Accelerated NPP declines are the result of both surface freshening and reductions in upwelling‐favorable winds enhancing phytoplankton nutrient limitation. Our findings indicate that including a dynamic Greenland ice sheet in ESMs could have large impacts on projections of future ocean circulation and biogeochemistry. Plain Language Summary Current projections of how primary production in the oceans will respond to climate change fail to account for the impact of melting continental ice sheets. Here we use an Earth System Model (ESM) to simulate the additional impact of Greenland ice melt on 21st century primary production. The addition of Greenland meltwaters causes an acceleration of projected primary production declines in the Atlantic Ocean under a high greenhouse gas emissions scenario. Our work indicates that previous projections of declining Atlantic primary production may have underestimated reductions by not accounting for Greenland meltwaters. Key Points Projected declines in Atlantic primary production are exacerbated by simulated Greenland ice sheet melt over the 21st century Greenland meltwater increases phytoplankton nutrient limitation by enhancing stratification and reducing upwelling‐promoting winds Enhanced nutrient limitation predominately suppresses primary production in Atlantic gyres and eastern boundary upwelling systems