A First Intercomparison of the Simulated LGM Carbon Results Within PMIP-Carbon: Role of the Ocean Boundary Conditions

F. Lhardy; N. Bouttes; D. M. Roche; A. Abe-Ouchi; Z. Chase; K. A. Crichton; T. Ilyina; R. Ivanovic; M. Jochum; M. Kageyama; H. Kobayashi; B. Liu; L. Menviel; J. Muglia; R. Nuterman; A. Oka; G. Vettoretti; A. Yamamoto

doi:10.1029/2021PA004302

A First Intercomparison of the Simulated LGM Carbon Results Within PMIP-Carbon: Role of the Ocean Boundary Conditions

F. Lhardy^*, N. Bouttes, D. M. Roche, A. Abe-Ouchi, Z. Chase, K. A. Crichton, T. Ilyina, R. Ivanovic, M. Jochum, M. Kageyama, H. Kobayashi, B. Liu, L. Menviel, J. Muglia, R. Nuterman, A. Oka, G. Vettoretti, A. Yamamoto

^*Corresponding author for this work

Earth Sciences

Research output: Contribution to Journal › Article › Academic › peer-review

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Abstract

Model intercomparison studies of coupled carbon-climate simulations have the potential to improve our understanding of the processes explaining the (Formula presented.) drawdown at the Last Glacial Maximum (LGM) and to identify related model biases. Models participating in the Paleoclimate Modeling Intercomparison Project (PMIP) now frequently include the carbon cycle. The ongoing PMIP-carbon project provides the first opportunity to conduct multimodel comparisons of simulated carbon content for the LGM time window. However, such a study remains challenging due to differing implementation of ocean boundary conditions (e.g., bathymetry and coastlines reflecting the low sea level) and to various associated adjustments of biogeochemical variables (i.e., alkalinity, nutrients, dissolved inorganic carbon). After assessing the ocean volume of PMIP models at the pre-industrial and LGM, we investigate the impact of these modeling choices on the simulated carbon at the global scale, using both PMIP-carbon model outputs and sensitivity tests with the iLOVECLIM model. We show that the carbon distribution in reservoirs is significantly affected by the choice of ocean boundary conditions in iLOVECLIM. In particular, our simulations demonstrate a (Formula presented.) GtC effect of an alkalinity adjustment on carbon sequestration in the ocean. Finally, we observe that PMIP-carbon models with a freely evolving (Formula presented.) and no additional glacial mechanisms do not simulate the (Formula presented.) drawdown at the LGM (with concentrations as high as 313, 331, and 315 ppm), especially if they use a low ocean volume. Our findings suggest that great care should be taken on accounting for large bathymetry changes in models including the carbon cycle.

Original language	English
Article number	e2021PA004302
Pages (from-to)	1-15
Number of pages	15
Journal	Paleoceanography and Paleoclimatology
Volume	36
Issue number	10
Early online date	17 Sept 2021
DOIs	https://doi.org/10.1029/2021PA004302
Publication status	Published - Oct 2021

Bibliographical note

Funding Information:
F. Lhardy, N. Bouttes, and D. M. Roche designed the research. N. Bouttes coordinated the PMIP‐carbon project and obtained funding. Participating modeling groups all performed a PI and a LGM simulation, provided their model outputs and the relevant metadata and computed the equilibrated carbon content in reservoirs. These modeling groups included AA‐O, HK, and AO (MIROC4m‐COCO); KC (CLIMBER‐2); MJ, RN, GV, and ZC (CESM); BL and TI (MPI‐ESM); MK (IPSL‐CM5A2); AY (MIROC‐ES2L); LM (LOVECLIM); JM and AS (UVic). F. Lhardy, D. M. Roche, and N. Bouttes generated new boundary conditions in the iLOVECLIM model. N. Bouttes and D. M. Roche developed the automated adjustments to allow for a change of ocean boundary conditions. F. Lhardy ran the iLOVECLIM simulations and analyzed both the iLOVECLIM and the PMIP‐carbon outputs under supervision of N. Bouttes and D. M. Roche. F. Lhardy wrote the manuscript with the inputs from all co‐authors. This study was supported by the French National program LEFE (Les Enveloppes Fluides et l'Environnement). F. Lhardy is supported by the Université Versailles Saint‐Quentin‐en‐Yvelines (UVSQ). N. Bouttes and D. M. Roche are supported by the Centre national de la recherche scientifique (CNRS). In addition, D. M. Roche is supported by the Vrije Universiteit Amsterdam. B. Liu and T. Ilyina are supported by the German Federal Ministry of Education and Research (PalMod initiative, FKZ: 420 grant no. 01LP1919B). L. Menviel acknowledges funding from the Australian Research Council grant FT180100606. A. Yamamoto acknowledges funding from the Integrated Research Program for Advancing Climate Models (TOUGOU) Grant Number JPMXD0717935715 from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The authors acknowledge the use of the LSCE storage and computing facilities. The authors thank Théo Mandonnet for his preliminary work on the PMIP‐carbon project. Last but not least, the authors thank the two anonymous reviewers for their help with this manuscript.

Funding Information:
F. Lhardy, N. Bouttes, and D. M. Roche designed the research. N. Bouttes coordinated the PMIP-carbon project and obtained funding. Participating modeling groups all performed a PI and a LGM simulation, provided their model outputs and the relevant metadata and computed the equilibrated carbon content in reservoirs. These modeling groups included AA-O, HK, and AO (MIROC4m-COCO); KC (CLIMBER-2); MJ, RN, GV, and ZC (CESM); BL and TI (MPI-ESM); MK (IPSL-CM5A2); AY (MIROC-ES2L); LM (LOVECLIM); JM and AS (UVic). F. Lhardy, D. M. Roche, and N. Bouttes generated new boundary conditions in the iLOVECLIM model. N. Bouttes and D. M. Roche developed the automated adjustments to allow for a change of ocean boundary conditions. F. Lhardy ran the iLOVECLIM simulations and analyzed both the iLOVECLIM and the PMIP-carbon outputs under supervision of N. Bouttes and D. M. Roche. F. Lhardy wrote the manuscript with the inputs from all co-authors. This study was supported by the French National program LEFE (Les Enveloppes Fluides et l'Environnement). F. Lhardy is supported by the Universit? Versailles Saint-Quentin-en-Yvelines (UVSQ). N. Bouttes and D. M. Roche are supported by the Centre national de la recherche scientifique (CNRS). In addition, D. M. Roche is supported by the Vrije Universiteit Amsterdam. B. Liu and T. Ilyina are supported by the German Federal Ministry of Education and Research (PalMod initiative, FKZ: 420 grant no. 01LP1919B). L. Menviel acknowledges funding from the Australian Research Council grant FT180100606. A. Yamamoto acknowledges funding from the Integrated Research Program for Advancing Climate Models (TOUGOU) Grant Number JPMXD0717935715 from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The authors acknowledge the use of the LSCE storage and computing facilities. The authors thank Th?o Mandonnet for his preliminary work on the PMIP-carbon project. Last but not least, the authors thank the two anonymous reviewers for their help with this manuscript.

Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.

Funding

F. Lhardy, N. Bouttes, and D. M. Roche designed the research. N. Bouttes coordinated the PMIP‐carbon project and obtained funding. Participating modeling groups all performed a PI and a LGM simulation, provided their model outputs and the relevant metadata and computed the equilibrated carbon content in reservoirs. These modeling groups included AA‐O, HK, and AO (MIROC4m‐COCO); KC (CLIMBER‐2); MJ, RN, GV, and ZC (CESM); BL and TI (MPI‐ESM); MK (IPSL‐CM5A2); AY (MIROC‐ES2L); LM (LOVECLIM); JM and AS (UVic). F. Lhardy, D. M. Roche, and N. Bouttes generated new boundary conditions in the iLOVECLIM model. N. Bouttes and D. M. Roche developed the automated adjustments to allow for a change of ocean boundary conditions. F. Lhardy ran the iLOVECLIM simulations and analyzed both the iLOVECLIM and the PMIP‐carbon outputs under supervision of N. Bouttes and D. M. Roche. F. Lhardy wrote the manuscript with the inputs from all co‐authors. This study was supported by the French National program LEFE (Les Enveloppes Fluides et l'Environnement). F. Lhardy is supported by the Université Versailles Saint‐Quentin‐en‐Yvelines (UVSQ). N. Bouttes and D. M. Roche are supported by the Centre national de la recherche scientifique (CNRS). In addition, D. M. Roche is supported by the Vrije Universiteit Amsterdam. B. Liu and T. Ilyina are supported by the German Federal Ministry of Education and Research (PalMod initiative, FKZ: 420 grant no. 01LP1919B). L. Menviel acknowledges funding from the Australian Research Council grant FT180100606. A. Yamamoto acknowledges funding from the Integrated Research Program for Advancing Climate Models (TOUGOU) Grant Number JPMXD0717935715 from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The authors acknowledge the use of the LSCE storage and computing facilities. The authors thank Théo Mandonnet for his preliminary work on the PMIP‐carbon project. Last but not least, the authors thank the two anonymous reviewers for their help with this manuscript. F. Lhardy, N. Bouttes, and D. M. Roche designed the research. N. Bouttes coordinated the PMIP-carbon project and obtained funding. Participating modeling groups all performed a PI and a LGM simulation, provided their model outputs and the relevant metadata and computed the equilibrated carbon content in reservoirs. These modeling groups included AA-O, HK, and AO (MIROC4m-COCO); KC (CLIMBER-2); MJ, RN, GV, and ZC (CESM); BL and TI (MPI-ESM); MK (IPSL-CM5A2); AY (MIROC-ES2L); LM (LOVECLIM); JM and AS (UVic). F. Lhardy, D. M. Roche, and N. Bouttes generated new boundary conditions in the iLOVECLIM model. N. Bouttes and D. M. Roche developed the automated adjustments to allow for a change of ocean boundary conditions. F. Lhardy ran the iLOVECLIM simulations and analyzed both the iLOVECLIM and the PMIP-carbon outputs under supervision of N. Bouttes and D. M. Roche. F. Lhardy wrote the manuscript with the inputs from all co-authors. This study was supported by the French National program LEFE (Les Enveloppes Fluides et l'Environnement). F. Lhardy is supported by the Universit? Versailles Saint-Quentin-en-Yvelines (UVSQ). N. Bouttes and D. M. Roche are supported by the Centre national de la recherche scientifique (CNRS). In addition, D. M. Roche is supported by the Vrije Universiteit Amsterdam. B. Liu and T. Ilyina are supported by the German Federal Ministry of Education and Research (PalMod initiative, FKZ: 420 grant no. 01LP1919B). L. Menviel acknowledges funding from the Australian Research Council grant FT180100606. A. Yamamoto acknowledges funding from the Integrated Research Program for Advancing Climate Models (TOUGOU) Grant Number JPMXD0717935715 from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The authors acknowledge the use of the LSCE storage and computing facilities. The authors thank Th?o Mandonnet for his preliminary work on the PMIP-carbon project. Last but not least, the authors thank the two anonymous reviewers for their help with this manuscript.

Funders	Funder number
Les Enveloppes Fluides et l'Environnement
MPI-ESM	IPSL-CM5A2
Australian Research Council	FT180100606, JPMXD0717935715
Ministry of Education, Culture, Sports, Science and Technology
Bundesministerium für Bildung und Forschung	01LP1919B
Centre National de la Recherche Scientifique
Université de Versailles Saint-Quentin-en-Yvelines

Keywords

alkalinity
atmospheric CO
carbon cycle
climate models
glacial-interglacial cycles
ocean volume

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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Paleoceanog and Paleoclimatol - 2021 - Lhardy - A First Intercomparison of the Simulated LGM Carbon Results WithinFinal published version, 1.26 MBLicence: Article 25fa Dutch Copyright Act

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Lhardy, F., Bouttes, N., Roche, D. M., Abe-Ouchi, A., Chase, Z., Crichton, K. A., Ilyina, T., Ivanovic, R., Jochum, M., Kageyama, M., Kobayashi, H., Liu, B., Menviel, L., Muglia, J., Nuterman, R., Oka, A., Vettoretti, G., & Yamamoto, A. (2021). A First Intercomparison of the Simulated LGM Carbon Results Within PMIP-Carbon: Role of the Ocean Boundary Conditions. Paleoceanography and Paleoclimatology, 36(10), 1-15. Article e2021PA004302. https://doi.org/10.1029/2021PA004302

@article{01dd560815944a84a82c1af44375881c,

title = "A First Intercomparison of the Simulated LGM Carbon Results Within PMIP-Carbon: Role of the Ocean Boundary Conditions",

abstract = "Model intercomparison studies of coupled carbon-climate simulations have the potential to improve our understanding of the processes explaining the (Formula presented.) drawdown at the Last Glacial Maximum (LGM) and to identify related model biases. Models participating in the Paleoclimate Modeling Intercomparison Project (PMIP) now frequently include the carbon cycle. The ongoing PMIP-carbon project provides the first opportunity to conduct multimodel comparisons of simulated carbon content for the LGM time window. However, such a study remains challenging due to differing implementation of ocean boundary conditions (e.g., bathymetry and coastlines reflecting the low sea level) and to various associated adjustments of biogeochemical variables (i.e., alkalinity, nutrients, dissolved inorganic carbon). After assessing the ocean volume of PMIP models at the pre-industrial and LGM, we investigate the impact of these modeling choices on the simulated carbon at the global scale, using both PMIP-carbon model outputs and sensitivity tests with the iLOVECLIM model. We show that the carbon distribution in reservoirs is significantly affected by the choice of ocean boundary conditions in iLOVECLIM. In particular, our simulations demonstrate a (Formula presented.) GtC effect of an alkalinity adjustment on carbon sequestration in the ocean. Finally, we observe that PMIP-carbon models with a freely evolving (Formula presented.) and no additional glacial mechanisms do not simulate the (Formula presented.) drawdown at the LGM (with concentrations as high as 313, 331, and 315 ppm), especially if they use a low ocean volume. Our findings suggest that great care should be taken on accounting for large bathymetry changes in models including the carbon cycle.",

keywords = "alkalinity, atmospheric CO, carbon cycle, climate models, glacial-interglacial cycles, ocean volume",

author = "F. Lhardy and N. Bouttes and Roche, {D. M.} and A. Abe-Ouchi and Z. Chase and Crichton, {K. A.} and T. Ilyina and R. Ivanovic and M. Jochum and M. Kageyama and H. Kobayashi and B. Liu and L. Menviel and J. Muglia and R. Nuterman and A. Oka and G. Vettoretti and A. Yamamoto",

note = "Funding Information: F. Lhardy, N. Bouttes, and D. M. Roche designed the research. N. Bouttes coordinated the PMIP‐carbon project and obtained funding. Participating modeling groups all performed a PI and a LGM simulation, provided their model outputs and the relevant metadata and computed the equilibrated carbon content in reservoirs. These modeling groups included AA‐O, HK, and AO (MIROC4m‐COCO); KC (CLIMBER‐2); MJ, RN, GV, and ZC (CESM); BL and TI (MPI‐ESM); MK (IPSL‐CM5A2); AY (MIROC‐ES2L); LM (LOVECLIM); JM and AS (UVic). F. Lhardy, D. M. Roche, and N. Bouttes generated new boundary conditions in the iLOVECLIM model. N. Bouttes and D. M. Roche developed the automated adjustments to allow for a change of ocean boundary conditions. F. Lhardy ran the iLOVECLIM simulations and analyzed both the iLOVECLIM and the PMIP‐carbon outputs under supervision of N. Bouttes and D. M. Roche. F. Lhardy wrote the manuscript with the inputs from all co‐authors. This study was supported by the French National program LEFE (Les Enveloppes Fluides et l'Environnement). F. Lhardy is supported by the Universit{\'e} Versailles Saint‐Quentin‐en‐Yvelines (UVSQ). N. Bouttes and D. M. Roche are supported by the Centre national de la recherche scientifique (CNRS). In addition, D. M. Roche is supported by the Vrije Universiteit Amsterdam. B. Liu and T. Ilyina are supported by the German Federal Ministry of Education and Research (PalMod initiative, FKZ: 420 grant no. 01LP1919B). L. Menviel acknowledges funding from the Australian Research Council grant FT180100606. A. Yamamoto acknowledges funding from the Integrated Research Program for Advancing Climate Models (TOUGOU) Grant Number JPMXD0717935715 from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The authors acknowledge the use of the LSCE storage and computing facilities. The authors thank Th{\'e}o Mandonnet for his preliminary work on the PMIP‐carbon project. Last but not least, the authors thank the two anonymous reviewers for their help with this manuscript. Funding Information: F. Lhardy, N. Bouttes, and D. M. Roche designed the research. N. Bouttes coordinated the PMIP-carbon project and obtained funding. Participating modeling groups all performed a PI and a LGM simulation, provided their model outputs and the relevant metadata and computed the equilibrated carbon content in reservoirs. These modeling groups included AA-O, HK, and AO (MIROC4m-COCO); KC (CLIMBER-2); MJ, RN, GV, and ZC (CESM); BL and TI (MPI-ESM); MK (IPSL-CM5A2); AY (MIROC-ES2L); LM (LOVECLIM); JM and AS (UVic). F. Lhardy, D. M. Roche, and N. Bouttes generated new boundary conditions in the iLOVECLIM model. N. Bouttes and D. M. Roche developed the automated adjustments to allow for a change of ocean boundary conditions. F. Lhardy ran the iLOVECLIM simulations and analyzed both the iLOVECLIM and the PMIP-carbon outputs under supervision of N. Bouttes and D. M. Roche. F. Lhardy wrote the manuscript with the inputs from all co-authors. This study was supported by the French National program LEFE (Les Enveloppes Fluides et l'Environnement). F. Lhardy is supported by the Universit? Versailles Saint-Quentin-en-Yvelines (UVSQ). N. Bouttes and D. M. Roche are supported by the Centre national de la recherche scientifique (CNRS). In addition, D. M. Roche is supported by the Vrije Universiteit Amsterdam. B. Liu and T. Ilyina are supported by the German Federal Ministry of Education and Research (PalMod initiative, FKZ: 420 grant no. 01LP1919B). L. Menviel acknowledges funding from the Australian Research Council grant FT180100606. A. Yamamoto acknowledges funding from the Integrated Research Program for Advancing Climate Models (TOUGOU) Grant Number JPMXD0717935715 from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The authors acknowledge the use of the LSCE storage and computing facilities. The authors thank Th?o Mandonnet for his preliminary work on the PMIP-carbon project. Last but not least, the authors thank the two anonymous reviewers for their help with this manuscript. Publisher Copyright: {\textcopyright} 2021. American Geophysical Union. All Rights Reserved.",

year = "2021",

month = oct,

doi = "10.1029/2021PA004302",

language = "English",

volume = "36",

pages = "1--15",

journal = "Paleoceanography and Paleoclimatology",

issn = "2572-4517",

publisher = "John Wiley & Sons, Ltd",

number = "10",

}

Lhardy, F, Bouttes, N, Roche, DM, Abe-Ouchi, A, Chase, Z, Crichton, KA, Ilyina, T, Ivanovic, R, Jochum, M, Kageyama, M, Kobayashi, H, Liu, B, Menviel, L, Muglia, J, Nuterman, R, Oka, A, Vettoretti, G & Yamamoto, A 2021, 'A First Intercomparison of the Simulated LGM Carbon Results Within PMIP-Carbon: Role of the Ocean Boundary Conditions', Paleoceanography and Paleoclimatology, vol. 36, no. 10, e2021PA004302, pp. 1-15. https://doi.org/10.1029/2021PA004302

TY - JOUR

T1 - A First Intercomparison of the Simulated LGM Carbon Results Within PMIP-Carbon

T2 - Role of the Ocean Boundary Conditions

AU - Lhardy, F.

AU - Bouttes, N.

AU - Roche, D. M.

AU - Abe-Ouchi, A.

AU - Chase, Z.

AU - Crichton, K. A.

AU - Ilyina, T.

AU - Ivanovic, R.

AU - Jochum, M.

AU - Kageyama, M.

AU - Kobayashi, H.

AU - Liu, B.

AU - Menviel, L.

AU - Muglia, J.

AU - Nuterman, R.

AU - Oka, A.

AU - Vettoretti, G.

AU - Yamamoto, A.

N1 - Funding Information: F. Lhardy, N. Bouttes, and D. M. Roche designed the research. N. Bouttes coordinated the PMIP‐carbon project and obtained funding. Participating modeling groups all performed a PI and a LGM simulation, provided their model outputs and the relevant metadata and computed the equilibrated carbon content in reservoirs. These modeling groups included AA‐O, HK, and AO (MIROC4m‐COCO); KC (CLIMBER‐2); MJ, RN, GV, and ZC (CESM); BL and TI (MPI‐ESM); MK (IPSL‐CM5A2); AY (MIROC‐ES2L); LM (LOVECLIM); JM and AS (UVic). F. Lhardy, D. M. Roche, and N. Bouttes generated new boundary conditions in the iLOVECLIM model. N. Bouttes and D. M. Roche developed the automated adjustments to allow for a change of ocean boundary conditions. F. Lhardy ran the iLOVECLIM simulations and analyzed both the iLOVECLIM and the PMIP‐carbon outputs under supervision of N. Bouttes and D. M. Roche. F. Lhardy wrote the manuscript with the inputs from all co‐authors. This study was supported by the French National program LEFE (Les Enveloppes Fluides et l'Environnement). F. Lhardy is supported by the Université Versailles Saint‐Quentin‐en‐Yvelines (UVSQ). N. Bouttes and D. M. Roche are supported by the Centre national de la recherche scientifique (CNRS). In addition, D. M. Roche is supported by the Vrije Universiteit Amsterdam. B. Liu and T. Ilyina are supported by the German Federal Ministry of Education and Research (PalMod initiative, FKZ: 420 grant no. 01LP1919B). L. Menviel acknowledges funding from the Australian Research Council grant FT180100606. A. Yamamoto acknowledges funding from the Integrated Research Program for Advancing Climate Models (TOUGOU) Grant Number JPMXD0717935715 from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The authors acknowledge the use of the LSCE storage and computing facilities. The authors thank Théo Mandonnet for his preliminary work on the PMIP‐carbon project. Last but not least, the authors thank the two anonymous reviewers for their help with this manuscript. Funding Information: F. Lhardy, N. Bouttes, and D. M. Roche designed the research. N. Bouttes coordinated the PMIP-carbon project and obtained funding. Participating modeling groups all performed a PI and a LGM simulation, provided their model outputs and the relevant metadata and computed the equilibrated carbon content in reservoirs. These modeling groups included AA-O, HK, and AO (MIROC4m-COCO); KC (CLIMBER-2); MJ, RN, GV, and ZC (CESM); BL and TI (MPI-ESM); MK (IPSL-CM5A2); AY (MIROC-ES2L); LM (LOVECLIM); JM and AS (UVic). F. Lhardy, D. M. Roche, and N. Bouttes generated new boundary conditions in the iLOVECLIM model. N. Bouttes and D. M. Roche developed the automated adjustments to allow for a change of ocean boundary conditions. F. Lhardy ran the iLOVECLIM simulations and analyzed both the iLOVECLIM and the PMIP-carbon outputs under supervision of N. Bouttes and D. M. Roche. F. Lhardy wrote the manuscript with the inputs from all co-authors. This study was supported by the French National program LEFE (Les Enveloppes Fluides et l'Environnement). F. Lhardy is supported by the Universit? Versailles Saint-Quentin-en-Yvelines (UVSQ). N. Bouttes and D. M. Roche are supported by the Centre national de la recherche scientifique (CNRS). In addition, D. M. Roche is supported by the Vrije Universiteit Amsterdam. B. Liu and T. Ilyina are supported by the German Federal Ministry of Education and Research (PalMod initiative, FKZ: 420 grant no. 01LP1919B). L. Menviel acknowledges funding from the Australian Research Council grant FT180100606. A. Yamamoto acknowledges funding from the Integrated Research Program for Advancing Climate Models (TOUGOU) Grant Number JPMXD0717935715 from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The authors acknowledge the use of the LSCE storage and computing facilities. The authors thank Th?o Mandonnet for his preliminary work on the PMIP-carbon project. Last but not least, the authors thank the two anonymous reviewers for their help with this manuscript. Publisher Copyright: © 2021. American Geophysical Union. All Rights Reserved.

PY - 2021/10

Y1 - 2021/10

N2 - Model intercomparison studies of coupled carbon-climate simulations have the potential to improve our understanding of the processes explaining the (Formula presented.) drawdown at the Last Glacial Maximum (LGM) and to identify related model biases. Models participating in the Paleoclimate Modeling Intercomparison Project (PMIP) now frequently include the carbon cycle. The ongoing PMIP-carbon project provides the first opportunity to conduct multimodel comparisons of simulated carbon content for the LGM time window. However, such a study remains challenging due to differing implementation of ocean boundary conditions (e.g., bathymetry and coastlines reflecting the low sea level) and to various associated adjustments of biogeochemical variables (i.e., alkalinity, nutrients, dissolved inorganic carbon). After assessing the ocean volume of PMIP models at the pre-industrial and LGM, we investigate the impact of these modeling choices on the simulated carbon at the global scale, using both PMIP-carbon model outputs and sensitivity tests with the iLOVECLIM model. We show that the carbon distribution in reservoirs is significantly affected by the choice of ocean boundary conditions in iLOVECLIM. In particular, our simulations demonstrate a (Formula presented.) GtC effect of an alkalinity adjustment on carbon sequestration in the ocean. Finally, we observe that PMIP-carbon models with a freely evolving (Formula presented.) and no additional glacial mechanisms do not simulate the (Formula presented.) drawdown at the LGM (with concentrations as high as 313, 331, and 315 ppm), especially if they use a low ocean volume. Our findings suggest that great care should be taken on accounting for large bathymetry changes in models including the carbon cycle.

AB - Model intercomparison studies of coupled carbon-climate simulations have the potential to improve our understanding of the processes explaining the (Formula presented.) drawdown at the Last Glacial Maximum (LGM) and to identify related model biases. Models participating in the Paleoclimate Modeling Intercomparison Project (PMIP) now frequently include the carbon cycle. The ongoing PMIP-carbon project provides the first opportunity to conduct multimodel comparisons of simulated carbon content for the LGM time window. However, such a study remains challenging due to differing implementation of ocean boundary conditions (e.g., bathymetry and coastlines reflecting the low sea level) and to various associated adjustments of biogeochemical variables (i.e., alkalinity, nutrients, dissolved inorganic carbon). After assessing the ocean volume of PMIP models at the pre-industrial and LGM, we investigate the impact of these modeling choices on the simulated carbon at the global scale, using both PMIP-carbon model outputs and sensitivity tests with the iLOVECLIM model. We show that the carbon distribution in reservoirs is significantly affected by the choice of ocean boundary conditions in iLOVECLIM. In particular, our simulations demonstrate a (Formula presented.) GtC effect of an alkalinity adjustment on carbon sequestration in the ocean. Finally, we observe that PMIP-carbon models with a freely evolving (Formula presented.) and no additional glacial mechanisms do not simulate the (Formula presented.) drawdown at the LGM (with concentrations as high as 313, 331, and 315 ppm), especially if they use a low ocean volume. Our findings suggest that great care should be taken on accounting for large bathymetry changes in models including the carbon cycle.

KW - alkalinity

KW - atmospheric CO

KW - carbon cycle

KW - climate models

KW - glacial-interglacial cycles

KW - ocean volume

UR - http://www.scopus.com/inward/record.url?scp=85118272131&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85118272131&partnerID=8YFLogxK

U2 - 10.1029/2021PA004302

DO - 10.1029/2021PA004302

M3 - Article

AN - SCOPUS:85118272131

SN - 2572-4517

VL - 36

SP - 1

EP - 15

JO - Paleoceanography and Paleoclimatology

JF - Paleoceanography and Paleoclimatology

IS - 10

M1 - e2021PA004302

ER -

A First Intercomparison of the Simulated LGM Carbon Results Within PMIP-Carbon: Role of the Ocean Boundary Conditions

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