On the propagation of the climate change signal through the lower trophic level of the North Atlantic ecosystem and its implications to ecosystem function and habitat

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The impact of climate change under unmitigated conditions on the marine ecosystem is estimated on the base of a model ensemble projection including two members of different levels of ecosystem complexity (MEDUSA and ERSEM), both forced using the atmospheric conditions of a high radiation scenario AR5 RCP8.5 from a coupled ESM.The evolution of the ecosystem of the North Atlantic is investigated using two different levels of biogeographic classifications. The first is based on ecosystem function and shows the functional changes across the basin, while the second is based on typical habitat indicators and therefore illustrated the impact of the changing conditions on higher trophic level habitats. The results show significant northward shifts of temperate and (sub-) tropical regimes, while the sub-polar regimes are expected to vanish towards the end of the century. Implications for ecosystem services are substantial as changes can be expected to lead to significant reductions in productivity and available biomass of the marine ecosystem, reductions in the potential of carbon sequestration and reductions of the favourable habitats for cold water species.