Observed and Projected Physical Oceanic Changes Related to Climate Change as Assessed in SROCC

Robert Hallberg, Geophysical Fluid Dynamics Laboratory, Princeton, United States, Javier Aristegui, Instituto de Oceanografía y Cambio Global (IOCAG), Universidad de Las Palmas de Gran Canaria, Las Palmas, Spain, Nathaniel L. Bindoff, Univ Tasmania, Hobart, TAS, Australia, William W.L. Cheung, The University of British Columbia, Institute for the Oceans and Fisheries, Vancouver, BC, Canada, Nathalie Hilmi, Consejo Nacional de Investigaciones Científicas y Técnicas, Monaco, Monaco, Nathalie Hilmi, Monaco Scientific Centre, Monaco, Monaco, Nianzhi Jiao, Xiamen University, Xiamen, China, James G. Kairo, Kenya Marine and Fisheries Institute, Kenya, Saiful Karim, Queensland University of Technology, Brisbane, QLD, Australia, Lisa A Levin, Scripps Institution of Oceanography, University of California San Diego, La Jolla, United States, Sean ODonoghue, Climate Change Adaptation Branch City of Durban, Durban, South Africa, Sara Purca Cuicapusa, Instituto del Mar del Peru, Peru, Baruch Rinkevich, Israel Oceanographic and Limnological Research, Haifa, Israel, Toshio Suga, Tohoku University, Graduate School of Science, Sendai, Japan, Alessandro Tagliabue, University of Liverpool, Earth, Ocean and Ecological Sciences, Liverpool, L69, United Kingdom and Phillip Williamson, University of East Anglia, Norwich, United Kingdom
Abstract:
The oceans are very likely warming at an accelerating rate since 1993, leading to rising sea levels and significant impacts on marine ecosystems. The IPCC Special Report on the Oceans and Cryosphere in a Changing Climate (SROCC) synthesizes new evidence since the Fifth Assessment Report to assess observed and projected changes in the ocean related to climate change; this talk presents key findings from this report about changes in the physical state of the ocean.

It is virtually certain that the upper 2000 m of the ocean has continued to warm since 2005. There is increased confidence that the ocean as a whole has warmed continuously over the past 5 decades at rates that are consistent with climate models. Observed 50-year regional patterns of warming averaged over the top 700 m are distinguishable from natural variability over most of the globe and are very likely attributable to human influences. Basin-scale warming between 700 m and 2000 m over the past 15 years is distinguishable from natural variability. The deep and abyssal ocean warming below 2000 m since the 1980s have been strongest in the Southern Ocean. By 2100 the ocean is very likely to warm by 2 to 4 times as much for low greenhouse gas emissions (RCP2.6) and 5 to 7 times as much for a high emissions scenario (RCP8.5) compared with the observed changes since 1970.

On average, the stratification of the upper 200 m of the ocean has increased by 2.30±0.12% since 1970 as a result of surface-intensified warming and salinity changes, and it is projected to increase by 12 to 30% by 2100 for RCP8.5. This increased stratification tends to restrict surface nutrient supply and reduce interior ocean oxygen content. Most wind driven circulations are projected not to differ dramatically from today, even as important buoyancy driven circulations, such as the Atlantic Meridional Overturning Circulation and Antarctic Bottom Water Cell, are projected to weaken. Coastal tidal amplitudes and patterns will exhibit statistically significant changes over the 21st century, impacting coastal ecosystems and human communities. The main results reported here are qualitatively robust to key sources of scientific uncertainty in projections of oceanic changes. Many of these oceanic changes are committed to continue throughout the 21st century, with magnitudes that depend strongly on forcing scenarios.

Back to: Key Findings of the IPCC Special Report on Ocean and Cryosphere in a Changing Climate: Challenges, Opportunities, and Future Scenarios I Posters