Winners and losers in marine ecosystems: the response of functional groups to an AMOC weakening under future emission scenarios

Climate change increases the risk of passing tipping points, such as the Atlantic Meridional Overturning Circulation (AMOC), which would lead to additional changes in the climate system. Tipping of the AMOC significantly alters the heat distribution on Earth, as well as the mixing and advection of nutrients in the ocean. These changes impact marine ecosystems that support the Earth system and society, posing an additional threat to environments that are already under pressure. Here, we look at the effect of an AMOC weakening on marine ecosystems by forcing the Community Earth System Model v2 (CESM2) with low (SSP1-2.6) and high (SSP5-8.5) emission scenarios from 2015 to 2100. For each emission scenario we have two types of simulations: (1) a control simulation with emissions only; and (2) a hosing simulation in which an additional freshwater flux is added in the North Atlantic to induce an extra weakening of the AMOC. We use the temperature and phytoplankton fields of the CESM2 simulations to drive the marine ecosystem model EcoOcean. This model simulates 52 different functional groups that represent species on all trophic levels. EcoOcean allows us to get a good overview of the response of marine ecosystems to changes in the AMOC. Globally, marine ecosystems see a decrease in total biomass as a response to an AMOC weakening. However, the regional and functional group response can deviate from the global mean, meaning that in some regions and for some groups biomass actually increases. We present an overview of the winners and losers in marine ecosystems in response to an AMOC weakening with potential consequences for the fishery industry and society.