Collapse of deep convection in the North Atlantic leads to ecological system reorganization under future emission scenarios

Marine ecosystems services are under threat from anthropogenic activities, such as warming induced by greenhouse gas emissions. This warming might also trigger non-linear tipping behavior in the Earth system. One of the elements that can show tipping behavior is the North Atlantic Subpolar Gyre (SPG). Through a shutdown of deep convection, we study such collapses under a low and high future emission scenario in the Community Earth System Model v2 (CESM2). The results of the CESM2 are used as input in EcoOcean, a marine ecosystem model. We find that a collapse of deep convection leads to a regime shift in the North Atlantic where diatoms are replaced by small phytoplankton as the dominant phytoplankton group. The regime shift is accompanied by a net decrease in total phytoplankton biomass of 45% and 53% in the low and high emission scenarios, respectively. A contrasting response is found on higher trophic levels where total consumer and commercial biomass do not follow the trend of total phytoplankton biomass. Total consumer biomass shows changes over the simulation of +13% and -12% for the low and high emission scenario, respectively. The contrasting response is related to the dominant functional groups in the SPG region being more responsive to changes in small phytoplankton biomass than to changes in diatom biomass. The net response to tipping of the SPG can surprisingly be an increase in biomass illustrating that tipping in the physical climate system can influence ecosystems in the North Atlantic in a non-linear way.

Recommended citation: Boot, A.A., and Dijkstra, H. A.: Collapse of deep convection in the North Atlantic leads to ecological system reorganization under future emission scenarios. ESS Open Archive. 24 December 2025. DOI: https://doi.org/10.22541/essoar.176659546.63479861/v1
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