Role of mode and intermediate waters in future ocean acidification: Analysis of CMIP5 models

• Published in: Geophysical Research Letters
• Main Authors: Resplandy, L., Bopp, L., Orr, J. C., Dunne, J. P.
• Other Authors: Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Modelling the Earth Response to Multiple Anthropogenic Interactions and Dynamics (MERMAID), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), NOAA Geophysical Fluid Dynamics Laboratory (GFDL), National Oceanic and Atmospheric Administration (NOAA)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Ocean acidification
• Online Access: https://hal.science/hal-03209735; https://hal.science/hal-03209735/document; https://hal.science/hal-03209735/file/grl.50414.pdf; https://doi.org/10.1002/grl.50414

International audience Consistent with recent observations, Coupled Model Intercomparison Project 5 Earth System Models project highest acidification rates in subsurface waters. Using seven Earth System Models, we find that high acidification rates in mode and intermediate waters (MIW) on centennial time scales (−0.0008 to −0.0023 ± 0.0001 yr−1 depending on the scenario) are predominantly explained by the geochemical effect of increasing atmospheric CO2, whereas physical and biological climate change feedbacks explain less than 10% of the simulated changes. MIW are characterized by a larger surface area to volume ratio than deep and bottom waters leading to 5 to 10 times larger carbon uptake. In addition, MIW geochemical properties result in a sensitivity to increasing carbon concentration twice larger than surface waters (ΔH+ of +1.2×10−4 mmol m−3 for every mmol m−3 of dissolved carbon in MIW versus +0.6×10−4 in surface waters). Low pH transported by mode and intermediate waters is likely to influence surface pH in upwelling regions decades after their isolation from the atmosphere.