Enhance seasonal amplitude of atmospheric CO2 by the changing Southern Ocean carbon sink

• Published in: Science Advances
• Main Authors: Yun, Jeongmin, Jeong, Sujong, Gruber, Nicolas, Gregor, Luke, Ho, Chang Hoi, Piao, Shilong, Ciais, Philippe, Schimel, David S., Kwon, Eun-Young
• Other Authors: Seoul National University Seoul (SNU), Departement Erdwissenschaften ETH Zürich (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology Zürich (ETH Zürich), Peking University Beijing, Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), California Institute of Technology (CALTECH), Pusan National University
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: [SDU]Sciences of the Universe [physics]; Ocean acidification; Southern Ocean
• Online Access: https://hal.science/hal-03837168; https://hal.science/hal-03837168/document; https://hal.science/hal-03837168/file/sciadv.abq0220.pdf; https://doi.org/10.1126/sciadv.abq0220

International audience The enhanced seasonal amplitude of atmospheric CO2 has been viewed so far primarily as a Northern Hemisphere phenomenon. Yet, analyses of atmospheric CO2 records from 49 stations between 1980 and 2018 reveal substantial trends and variations in this amplitude globally. While no significant trends can be discerned before 2000 in most places, strong positive trends emerge after 2000 in the southern high latitudes. Using factorial simulations with an atmospheric transport model and analyses of surface ocean Pco2 observations, we show that the increase is best explained by the onset of increasing seasonality of air-sea CO2 exchange over the Southern Ocean around 2000. Underlying these changes is the long-term ocean acidification trend that tends to enhance the seasonality of the air-sea fluxes, but this trend is modified by the decadal variability of the Southern Ocean carbon sink. The seasonal variations of atmospheric CO2 thus emerge as a sensitive recorder of the variations of the Southern Ocean carbon sin