@article{504ea1491a45427187419215a123fb62,
title = "Projected Centennial Oxygen Trends and Their Attribution to Distinct Ocean Climate Forcings",
abstract = "We explore centennial changes in tropical Pacific oxygen (O2) using numerical models to illustrate the dominant patterns and mechanisms under centennial climate change. Future projections from state-of-the-art Earth System Models exhibit significant model to model differences, but decreased solubility and weakened ventilation together deplete thermocline O2 in middle to high latitudes. In contrast, the tropical thermocline O2 undergoes much smaller changes or even a slight increase. A suite of sensitivity experiments using a coarse resolution ocean circulation and biogeochemistry model show that ocean warming is the leading cause of global deoxygenation in the thermocline across all latitudes with secondary contributions from changes in hydrological cycles and wind stress modulating regional changes in O2. The small O2 changes in the tropical Pacific thermocline reflect near-complete compensation between the solubility decrease due to warming and reduction in apparent oxygen utilization (AOU). We further quantified the changes in AOU due to contributions from changes in water mass age and biological remineralization from the sensitivity experiments. The two effects almost equally contribute to the reduction of AOU in the tropical Pacific thermocline (43% for physical circulations and 57% for biology). Our results suggest that better understanding of water mass changes in the tropical oceans is key to improving projections and reducing the uncertainties of future O2 changes.",
keywords = "centennial timescale, climate change, oxygen trends",
author = "Yohei Takano and Takamitsu Ito and Curtis Deutsch",
note = "Funding Information: The main part of this study is carried out during the first author's Ph.D. study at Georgia Institute of Technology. We thank Hartmut Frenzel for his technical support with the data processing of the CMIP5 archive and comments on the manuscript. We would also like to thank two anonymous reviewers for critical and constructive comments on the initial version of the manuscript. We acknowledge the World Climate Research Programme's Working Group on Coupled Modeling, which is responsible for CMIP5, and we thank the climate modeling groups (listed in Table) for producing and making available their model output. For CMIP5 the U.S. Department of Energy's Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals. Some figures are visualized using the NCAR Command Language (NCL). The model output from the sensitivity experiments used in this study could be accessed from the Georgia Tech website (http://shadow.eas.gatech.edu/~Ito/webdata/data.html). YT's Ph.D. study and TI were supported by a grant from NSF (OCE-1357373) and CD was supported by grants from NSF (OCE-1458967 and OCE-1419323) and the Gordon and Betty Moore Foundation (GBMF #3775). YT's work at the Max Planck Institute for Meteorology are supported by the European Union's Horizon 2020 research and innovation programme under grant agreement No 641816 (CRESCENDO). Funding Information: The main part of this study is carried out during the first author{\textquoteright}s Ph.D. study at Georgia Institute of Technology. We thank Hartmut Frenzel for his technical support with the data processing of the CMIP5 archive and comments on the manuscript. We would also like to thank two anonymous reviewers for critical and constructive comments on the initial version of the manuscript. We acknowledge the World Climate Research Programme{\textquoteright}s Working Group on Coupled Modeling, which is responsible for CMIP5, and we thank the climate modeling groups (listed in Table 1) for producing and making available their model output. For CMIP5 the U.S. Department of Energy{\textquoteright}s Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals. Some figures are visualized using the NCAR Command Language (NCL). The model output from the sensitivity experiments used in this study could be accessed from the Georgia Tech website (http:// shadow.eas.gatech.edu/~Ito/webdata/ data.html). YT{\textquoteright}s Ph.D. study and TI were supported by a grant from NSF (OCE-1357373) and CD was supported by grants from NSF (OCE-1458967 and OCE-1419323) and the Gordon and Betty Moore Foundation (GBMF #3775). YT{\textquoteright}s work at the Max Planck Institute for Meteorology are supported by the European Union{\textquoteright}s Horizon 2020 research and innovation programme under grant agreement No 641816 (CRESCENDO). Publisher Copyright: {\textcopyright}2018. American Geophysical Union. All Rights Reserved.",
year = "2018",
month = sep,
doi = "10.1029/2018GB005939",
language = "English (US)",
volume = "32",
pages = "1329--1349",
journal = "Global Biogeochemical Cycles",
issn = "0886-6236",
publisher = "American Geophysical Union",
number = "9",
}