Vertical migration to reach cooler waters is a suitable strategy for some marine organisms to adapt to ocean warming. Here, we calculate that realized vertical isotherm migration rates averaged -6.6 + 18.8 m dec-1 across the global ocean between 1980 and 2015. Throughout this century (2006-2100), surface isotherms are projected to deepen at an increasing rate across the globe, averaging -32.3 m dec-1 under the representative concentration pathway (RCP)8.5 'business as usual' emissions scenario, and -18.7 m dec-1 under the more moderate RCP4.5 scenario. The vertical redistribution required by organisms to follow surface isotherms over this century is three to four orders of magnitude less than the equivalent horizontal redistribution distance. However, the seafloor depth and the depth of the photic layer pose ultimate limits to the vertical migration possible by species. Both limits will be reached by the end of this century across much of the ocean, leading to a rapid global compression of the three-dimensional (3D) habitat of many marine organisms. Phytoplankton diversity may be maintained but displaced toward the base of the photic layer, whereas highly productive benthic habitats, especially corals, will have their suitable 3D habitat rapidly reduced.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We thank the World Climate Research Programme for producing and making available the CMIP5 model output. This research has been partially funded by Spanish Projects CLIFISH (grant no. CTM2015-66400-C3-2-R), MedSHIFT (grant no. CGL2015- 71809-P), Fundación BBVA (Interbioclima project), European Union’s Horizon 2020 SOCLIMPACT project (grant agreement no. 776661) and King Abdullah University
of Science and Technology through baseline funding to C.M.D and S.A. S.B. received funding from the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 65924). J.S.G. was supported by a Juan de la Cierva Formación contract from the Spanish Ministry of Economy, Industry and Competiveness.