Assessing the Legacy Effects of Climate Change on the World's Oceans Utilizing Reversibility Scenarios

The oceans are key regulators of the Earth's climate and marine ecosystems provide highly-valued socio-economic services. Anthropogenic climate change has already impacted the ocean and earth system models project continued alteration under future carbon emissions scenarios. This has spurred consideration of diverse climate change mitigation strategies. Very little is known, however, about what would happen to our ocean under mitigation. The utility of idealized greenhouse gas reversibility scenarios to investigate processes driving responses under mitigation was demonstrated in a study by John et al. (2015), which showed that legacy effects of climate change continue even as mitigation is implemented under a reversal of the RCP8.5 scenario. Results will be presented from a multi-model reversibility intercomparison to assess the range of uncertainty in ocean responses in an idealized RCP8.5 mitigation projection. Additionally, results from an idealized ramp-up/ramp-down 1% to 4xCO2 simulation will be assessed to contrast and compare to the ramp-up/ramp-down RCP8.5 multi-model suite. Preliminary results show that broad-scale global temporal, spatial, and subsurface responses are robust across the multi-model suite for variables such as temperature. Regional responses such as oxygen in upwelling regions may differ across models however, and vastly different responses may be obtained (e.g. in net primary production), likely due to model structural differences. These initial results indicate that additional reversibility studies are needed to better understand and quantify climate, ocean, and ecosystem responses under mitigation.