Seasonal Variability of the Surface Ocean Carbon Cycle: A Synthesis

• Published in: Global Biogeochemical Cycles
• Main Authors: Rodgers, Keith B., Schwinger, Jörg, Fassbender, Andrea J., Landschützer, Peter, Yamaguchi, Ryohei, Frenzel, Hartmut, Stein, Karl, Müller, Jens Daniel Müller, Goris, Nadine, Sharma, Sahil, Bushinsky, Seth, Chau, Thi-Tuyet-Trang, Gehlen, Marion, Gallego, M. Angeles, Gloege, Lucas, Gregor, Luke, Gruber, Nicolas, Hauck, Judith, Iida, Yosuke, Ishii, Masao, Keppler, Lydia, Kim, Ji-Eun, Schlunegger, Sarah, Tjiputra, Jerry, Toyama, Katsuya, Ayar, Pradeebane Vaittinada, Velo, A.
• Other Authors: National Institute for Environmental Studies (Japan), Japan Agency for Marine-Earth Science and Technology, European Space Agency, Institute for Basic Science (South Korea), Research Council of Norway, National Oceanic and Atmospheric Administration (US), European Commission, Helmholtz Association, Environmental Restoration and Conservation Agency (Japan), Ministry of the Environment (Japan), Ministerio de Ciencia e Innovación (España)
• Format: Article in Journal/Newspaper
• Language: English
• Published: John Wiley & Sons 2023
• Subjects: Southern Ocean
• Online Access: http://hdl.handle.net/10261/336017; https://doi.org/10.1029/2023GB007798

34 pages, 13 figures, 6 tables.-- This is an open access article under the terms of the Creative Commons Attribution License The seasonal cycle is the dominant mode of variability in the air-sea CO2 flux in most regions of the global ocean, yet discrepancies between different seasonality estimates are rather large. As part of the Regional Carbon Cycle Assessment and Processes Phase 2 project (RECCAP2), we synthesize surface ocean pCO2 and air-sea CO2 flux seasonality from models and observation-based estimates, focusing on both a present-day climatology and decadal changes between the 1980s and 2010s. Four main findings emerge: First, global ocean biogeochemistry models (GOBMs) and observation-based estimates (pCO2 products) of surface pCO2 seasonality disagree in amplitude and phase, primarily due to discrepancies in the seasonal variability in surface DIC. Second, the seasonal cycle in pCO2 has increased in amplitude over the last three decades in both pCO2 products and GOBMs. Third, decadal increases in pCO2 seasonal cycle amplitudes in subtropical biomes for both pCO2 products and GOBMs are driven by increasing DIC concentrations stemming from the uptake of anthropogenic CO2 (Cant). In subpolar and Southern Ocean biomes, however, the seasonality change for GOBMs is dominated by Cant invasion, whereas for pCO2 products an indeterminate combination of Cant invasion and climate change modulates the changes. Fourth, biome-aggregated decadal changes in the amplitude of pCO2 seasonal variability are largely detectable against both mapping uncertainty (reducible) and natural variability uncertainty (irreducible), but not at the gridpoint scale over much of the northern subpolar oceans and over the Southern Ocean, underscoring the importance of sustained high-quality seasonally resolved measurements over these regions We would like to thank the financial sponsors of the original kickoff meeting for RECCAP2 in Gotemba Japan in March 2019, which facilitated not only this paper but the broader RECCAP2 synthesis ...