Mechanisms of millennial-scale atmospheric CO2 change in numerical model simulations
Numerical models are important tools for understanding the processes and feedbacks in the Earth system, including those involving changes in atmospheric CO2 (CO2,atm) concentrations. Here, we compile 55 published model studies (consisting of 778 individual simulations) that assess the impact of six...
Published in: | Quaternary Science Reviews |
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Elsevier
2019
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Online Access: | https://epic.awi.de/id/eprint/49979/ https://epic.awi.de/id/eprint/49979/1/gottschalk2019qsr.pdf https://hdl.handle.net/10013/epic.cec4523b-9960-4653-9503-1c9c5f47ea4c https://hdl.handle.net/ |
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Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) |
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description |
Numerical models are important tools for understanding the processes and feedbacks in the Earth system, including those involving changes in atmospheric CO2 (CO2,atm) concentrations. Here, we compile 55 published model studies (consisting of 778 individual simulations) that assess the impact of six forcing mechanisms on millennial-scale CO2,atm variations: changes in freshwater supply to the North Atlantic and Southern Ocean, the strength and position of the southern-hemisphere westerlies, Antarctic sea ice extent, and aeolian dust fluxes. We generally find agreement on the direction of simulated CO2,atm change across simulations, but the amplitude of change is inconsistent, primarily due to the different complexities of the model representation of Earth system processes. When freshwater is added to the North Atlantic, a reduced Atlantic Meridional Overturning Circulation (AMOC) is generally accompanied by an increase in Southern Ocean- and Pacific overturning, reduced Antarctic sea ice extent, spatially varying export production, and changes in carbon storage in the Atlantic (rising), in other ocean basins (generally decreasing) and on land (more varied). Positive or negative CO2,atm changes are simulated during AMOC minima due to a spatially and temporally varying dominance of individual terrestrial and oceanic drivers (and compensating effects between them) across the different models. In contrast, AMOC recoveries are often accompanied by rising CO2,atm levels, which are mostly driven by ocean carbon release (albeit from different regions). The magnitude of simulated CO2,atm rise broadly scales with the duration of the AMOC perturbation (i.e., the stadial length). When freshwater is added to the Southern Ocean, reduced deep-ocean ventilation drives a CO2,atm drop via reduced carbon release from the Southern Ocean. Although the impacts of shifted southern-hemisphere westerlies are inconsistent across model simulations, their intensification raises CO2,atm via enhanced Southern Ocean Ekman pumping. Increased supply of aeolian dust to the ocean, and thus iron fertilisation of marine productivity, consistently lowers modelled CO2,atm concentrations via more efficient nutrient utilisation. The magni- tude of CO2,atm change in response to dust flux variations, however, largely depends on the complexity of models' marine ecosystem and iron cycle. This especially applies to simulations forced by Antarctic sea ice changes, in which the direction of simulated CO2,atm change varies greatly across model hierarchies. Our compilation highlights that no single (forcing) mechanism can explain observed past millennial-scale CO2,atm variability, and identifies important future needs in coupled carbon cycle-climate modelling to better understand the mechanisms governing CO2,atm changes in the past. |
format |
Article in Journal/Newspaper |
author |
Gottschalk, Julia Battaglia, Gianna Fischer, Hubertus Frölicher, Thomas L. Jaccard, Samuel L. Jeltsch-Thömmes, Aurich Joos, Fortunat Köhler, Peter Meissner, Katrin J. Menviel, Laurie Nehrbass-Ahles, Christoph Schmitt, Jochen Schmittner, Andreas Skinner, Luke C. Stocker, Thomas F. |
spellingShingle |
Gottschalk, Julia Battaglia, Gianna Fischer, Hubertus Frölicher, Thomas L. Jaccard, Samuel L. Jeltsch-Thömmes, Aurich Joos, Fortunat Köhler, Peter Meissner, Katrin J. Menviel, Laurie Nehrbass-Ahles, Christoph Schmitt, Jochen Schmittner, Andreas Skinner, Luke C. Stocker, Thomas F. Mechanisms of millennial-scale atmospheric CO2 change in numerical model simulations |
author_facet |
Gottschalk, Julia Battaglia, Gianna Fischer, Hubertus Frölicher, Thomas L. Jaccard, Samuel L. Jeltsch-Thömmes, Aurich Joos, Fortunat Köhler, Peter Meissner, Katrin J. Menviel, Laurie Nehrbass-Ahles, Christoph Schmitt, Jochen Schmittner, Andreas Skinner, Luke C. Stocker, Thomas F. |
author_sort |
Gottschalk, Julia |
title |
Mechanisms of millennial-scale atmospheric CO2 change in numerical model simulations |
title_short |
Mechanisms of millennial-scale atmospheric CO2 change in numerical model simulations |
title_full |
Mechanisms of millennial-scale atmospheric CO2 change in numerical model simulations |
title_fullStr |
Mechanisms of millennial-scale atmospheric CO2 change in numerical model simulations |
title_full_unstemmed |
Mechanisms of millennial-scale atmospheric CO2 change in numerical model simulations |
title_sort |
mechanisms of millennial-scale atmospheric co2 change in numerical model simulations |
publisher |
Elsevier |
publishDate |
2019 |
url |
https://epic.awi.de/id/eprint/49979/ https://epic.awi.de/id/eprint/49979/1/gottschalk2019qsr.pdf https://hdl.handle.net/10013/epic.cec4523b-9960-4653-9503-1c9c5f47ea4c https://hdl.handle.net/ |
geographic |
Antarctic Pacific Southern Ocean |
geographic_facet |
Antarctic Pacific Southern Ocean |
genre |
Antarc* Antarctic North Atlantic Sea ice Southern Ocean |
genre_facet |
Antarc* Antarctic North Atlantic Sea ice Southern Ocean |
op_source |
EPIC3Quaternary Science Reviews, Elsevier, 220, pp. 30-74, ISSN: 02773791 |
op_relation |
https://epic.awi.de/id/eprint/49979/1/gottschalk2019qsr.pdf https://hdl.handle.net/ Gottschalk, J. , Battaglia, G. , Fischer, H. , Frölicher, T. L. , Jaccard, S. L. , Jeltsch-Thömmes, A. , Joos, F. , Köhler, P. orcid:0000-0003-0904-8484 , Meissner, K. J. , Menviel, L. , Nehrbass-Ahles, C. , Schmitt, J. , Schmittner, A. , Skinner, L. C. and Stocker, T. F. (2019) Mechanisms of millennial-scale atmospheric CO2 change in numerical model simulations , Quaternary Science Reviews, 220 , pp. 30-74 . doi:10.1016/j.quascirev.2019.05.013 <https://doi.org/10.1016/j.quascirev.2019.05.013> , hdl:10013/epic.cec4523b-9960-4653-9503-1c9c5f47ea4c |
op_doi |
https://doi.org/10.1016/j.quascirev.2019.05.013 |
container_title |
Quaternary Science Reviews |
container_volume |
220 |
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30 |
op_container_end_page |
74 |
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1766221717873623040 |
spelling |
ftawi:oai:epic.awi.de:49979 2023-05-15T13:45:21+02:00 Mechanisms of millennial-scale atmospheric CO2 change in numerical model simulations Gottschalk, Julia Battaglia, Gianna Fischer, Hubertus Frölicher, Thomas L. Jaccard, Samuel L. Jeltsch-Thömmes, Aurich Joos, Fortunat Köhler, Peter Meissner, Katrin J. Menviel, Laurie Nehrbass-Ahles, Christoph Schmitt, Jochen Schmittner, Andreas Skinner, Luke C. Stocker, Thomas F. 2019 application/pdf https://epic.awi.de/id/eprint/49979/ https://epic.awi.de/id/eprint/49979/1/gottschalk2019qsr.pdf https://hdl.handle.net/10013/epic.cec4523b-9960-4653-9503-1c9c5f47ea4c https://hdl.handle.net/ unknown Elsevier https://epic.awi.de/id/eprint/49979/1/gottschalk2019qsr.pdf https://hdl.handle.net/ Gottschalk, J. , Battaglia, G. , Fischer, H. , Frölicher, T. L. , Jaccard, S. L. , Jeltsch-Thömmes, A. , Joos, F. , Köhler, P. orcid:0000-0003-0904-8484 , Meissner, K. J. , Menviel, L. , Nehrbass-Ahles, C. , Schmitt, J. , Schmittner, A. , Skinner, L. C. and Stocker, T. F. (2019) Mechanisms of millennial-scale atmospheric CO2 change in numerical model simulations , Quaternary Science Reviews, 220 , pp. 30-74 . doi:10.1016/j.quascirev.2019.05.013 <https://doi.org/10.1016/j.quascirev.2019.05.013> , hdl:10013/epic.cec4523b-9960-4653-9503-1c9c5f47ea4c EPIC3Quaternary Science Reviews, Elsevier, 220, pp. 30-74, ISSN: 02773791 Article isiRev 2019 ftawi https://doi.org/10.1016/j.quascirev.2019.05.013 2021-12-24T15:44:50Z Numerical models are important tools for understanding the processes and feedbacks in the Earth system, including those involving changes in atmospheric CO2 (CO2,atm) concentrations. Here, we compile 55 published model studies (consisting of 778 individual simulations) that assess the impact of six forcing mechanisms on millennial-scale CO2,atm variations: changes in freshwater supply to the North Atlantic and Southern Ocean, the strength and position of the southern-hemisphere westerlies, Antarctic sea ice extent, and aeolian dust fluxes. We generally find agreement on the direction of simulated CO2,atm change across simulations, but the amplitude of change is inconsistent, primarily due to the different complexities of the model representation of Earth system processes. When freshwater is added to the North Atlantic, a reduced Atlantic Meridional Overturning Circulation (AMOC) is generally accompanied by an increase in Southern Ocean- and Pacific overturning, reduced Antarctic sea ice extent, spatially varying export production, and changes in carbon storage in the Atlantic (rising), in other ocean basins (generally decreasing) and on land (more varied). Positive or negative CO2,atm changes are simulated during AMOC minima due to a spatially and temporally varying dominance of individual terrestrial and oceanic drivers (and compensating effects between them) across the different models. In contrast, AMOC recoveries are often accompanied by rising CO2,atm levels, which are mostly driven by ocean carbon release (albeit from different regions). The magnitude of simulated CO2,atm rise broadly scales with the duration of the AMOC perturbation (i.e., the stadial length). When freshwater is added to the Southern Ocean, reduced deep-ocean ventilation drives a CO2,atm drop via reduced carbon release from the Southern Ocean. Although the impacts of shifted southern-hemisphere westerlies are inconsistent across model simulations, their intensification raises CO2,atm via enhanced Southern Ocean Ekman pumping. Increased supply of aeolian dust to the ocean, and thus iron fertilisation of marine productivity, consistently lowers modelled CO2,atm concentrations via more efficient nutrient utilisation. The magni- tude of CO2,atm change in response to dust flux variations, however, largely depends on the complexity of models' marine ecosystem and iron cycle. This especially applies to simulations forced by Antarctic sea ice changes, in which the direction of simulated CO2,atm change varies greatly across model hierarchies. Our compilation highlights that no single (forcing) mechanism can explain observed past millennial-scale CO2,atm variability, and identifies important future needs in coupled carbon cycle-climate modelling to better understand the mechanisms governing CO2,atm changes in the past. Article in Journal/Newspaper Antarc* Antarctic North Atlantic Sea ice Southern Ocean Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) Antarctic Pacific Southern Ocean Quaternary Science Reviews 220 30 74 |