The quiet crossing of ocean tipping points
- aGeophysical Institute, University of Bergen, 5020 Bergen, Norway;
- bBjerknes Centre for Climate Research, University of Bergen, 5020 Bergen, Norway;
- cStockholm Resilience Centre, Stockholm University, 10691 Stockholm, Sweden;
- dRossby Centre, Swedish Meteorological and Hydrological Institute, 60176 Norrköping, Sweden;
- eLaboratoire des Sciences du Climat et de l’Environnement, Institut Pierre Simon Laplace, 91191 Gif-sur-Yvette cedex, France;
- fInstitute of Biogeochemistry and Pollutant Dynamics, Eidgenössische Technische Hochschule (ETH) Zürich, 8092 Zürich, Switzerland;
- gPacific Centre for the Environment and Sustainable Development, The University of the South Pacific, Suva, Fiji;
- hNorwegian Meteorological Institute, 0371 Oslo, Norway;
- iThe Norwegian Academy of Science and Letters, 0271 Oslo, Norway;
- jClimate and Environmental Physics, Physics Institute, University of Bern, 3012 Bern, Switzerland;
- kOeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland;
- lSchool of Architecture, Computing and Engineering, University of East London, E16 2RD, London, United Kingdom;
- mArctic Monitoring and Assessment Programme Secretariat, 9296 Tromsø, Norway
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Edited by David M. Karl, University of Hawaii at Manoa, Honolulu, HI, and approved December 17, 2020 (received for review July 30, 2020)

Abstract
Anthropogenic climate change profoundly alters the ocean’s environmental conditions, which, in turn, impact marine ecosystems. Some of these changes are happening fast and may be difficult to reverse. The identification and monitoring of such changes, which also includes tipping points, is an ongoing and emerging research effort. Prevention of negative impacts requires mitigation efforts based on feasible research-based pathways. Climate-induced tipping points are traditionally associated with singular catastrophic events (relative to natural variations) of dramatic negative impact. High-probability high-impact ocean tipping points due to warming, ocean acidification, and deoxygenation may be more fragmented both regionally and in time but add up to global dimensions. These tipping points in combination with gradual changes need to be addressed as seriously as singular catastrophic events in order to prevent the cumulative and often compounding negative societal and Earth system impacts.
Footnotes
- ↵1To whom correspondence may be addressed. Email: christoph.heinze{at}uib.no.
Author contributions: C.H., T.B., H.M., D.R., R.D., M.G., N.G., E.H., Ø.H., F.J., J.B.R.M., R.R., and S.W. wrote the paper.
The authors declare no competing interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.2008478118/-/DCSupplemental.
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There are no data underlying this work.
- Copyright © 2021 the Author(s). Published by PNAS.
This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY).
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