Impact of brine-induced stratification on the glacial carbon cycle
During the cold period of the Last Glacial Maximum (LGM, about 21 000 years ago) atmospheric CO 2 was around 190 ppm, much lower than the pre-industrial concentration of 280 ppm. The causes of this substantial drop remain partially unresolved, despite intense research. Understanding the origin of re...
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ftcopernicus:oai:publications.copernicus.org:cp7258 2023-05-15T18:18:49+02:00 Impact of brine-induced stratification on the glacial carbon cycle Bouttes, N. Paillard, D. Roche, D. M. 2018-09-27 application/pdf https://doi.org/10.5194/cp-6-575-2010 https://cp.copernicus.org/articles/6/575/2010/ eng eng doi:10.5194/cp-6-575-2010 https://cp.copernicus.org/articles/6/575/2010/ eISSN: 1814-9332 Text 2018 ftcopernicus https://doi.org/10.5194/cp-6-575-2010 2020-07-20T16:26:21Z During the cold period of the Last Glacial Maximum (LGM, about 21 000 years ago) atmospheric CO 2 was around 190 ppm, much lower than the pre-industrial concentration of 280 ppm. The causes of this substantial drop remain partially unresolved, despite intense research. Understanding the origin of reduced atmospheric CO 2 during glacial times is crucial to comprehend the evolution of the different carbon reservoirs within the Earth system (atmosphere, terrestrial biosphere and ocean). In this context, the ocean is believed to play a major role as it can store large amounts of carbon, especially in the abyss, which is a carbon reservoir that is thought to have expanded during glacial times. To create this larger reservoir, one possible mechanism is to produce very dense glacial waters, thereby stratifying the deep ocean and reducing the carbon exchange between the deep and upper ocean. The existence of such very dense waters has been inferred in the LGM deep Atlantic from sediment pore water salinity and δ 18 O inferred temperature. Based on these observations, we study the impact of a brine mechanism on the glacial carbon cycle. This mechanism relies on the formation and rapid sinking of brines, very salty water released during sea ice formation, which brings salty dense water down to the bottom of the ocean. It provides two major features: a direct link from the surface to the deep ocean along with an efficient way of setting a strong stratification. We show with the CLIMBER-2 carbon-climate model that such a brine mechanism can account for a significant decrease in atmospheric CO 2 and contribute to the glacial-interglacial change. This mechanism can be amplified by low vertical diffusion resulting from the brine-induced stratification. The modeled glacial distribution of oceanic δ 13 C as well as the deep ocean salinity are substantially improved and better agree with reconstructions from sediment cores, suggesting that such a mechanism could have played an important role during glacial times. Text Sea ice Copernicus Publications: E-Journals Climate of the Past 6 5 575 589 |
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Copernicus Publications: E-Journals |
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English |
description |
During the cold period of the Last Glacial Maximum (LGM, about 21 000 years ago) atmospheric CO 2 was around 190 ppm, much lower than the pre-industrial concentration of 280 ppm. The causes of this substantial drop remain partially unresolved, despite intense research. Understanding the origin of reduced atmospheric CO 2 during glacial times is crucial to comprehend the evolution of the different carbon reservoirs within the Earth system (atmosphere, terrestrial biosphere and ocean). In this context, the ocean is believed to play a major role as it can store large amounts of carbon, especially in the abyss, which is a carbon reservoir that is thought to have expanded during glacial times. To create this larger reservoir, one possible mechanism is to produce very dense glacial waters, thereby stratifying the deep ocean and reducing the carbon exchange between the deep and upper ocean. The existence of such very dense waters has been inferred in the LGM deep Atlantic from sediment pore water salinity and δ 18 O inferred temperature. Based on these observations, we study the impact of a brine mechanism on the glacial carbon cycle. This mechanism relies on the formation and rapid sinking of brines, very salty water released during sea ice formation, which brings salty dense water down to the bottom of the ocean. It provides two major features: a direct link from the surface to the deep ocean along with an efficient way of setting a strong stratification. We show with the CLIMBER-2 carbon-climate model that such a brine mechanism can account for a significant decrease in atmospheric CO 2 and contribute to the glacial-interglacial change. This mechanism can be amplified by low vertical diffusion resulting from the brine-induced stratification. The modeled glacial distribution of oceanic δ 13 C as well as the deep ocean salinity are substantially improved and better agree with reconstructions from sediment cores, suggesting that such a mechanism could have played an important role during glacial times. |
format |
Text |
author |
Bouttes, N. Paillard, D. Roche, D. M. |
spellingShingle |
Bouttes, N. Paillard, D. Roche, D. M. Impact of brine-induced stratification on the glacial carbon cycle |
author_facet |
Bouttes, N. Paillard, D. Roche, D. M. |
author_sort |
Bouttes, N. |
title |
Impact of brine-induced stratification on the glacial carbon cycle |
title_short |
Impact of brine-induced stratification on the glacial carbon cycle |
title_full |
Impact of brine-induced stratification on the glacial carbon cycle |
title_fullStr |
Impact of brine-induced stratification on the glacial carbon cycle |
title_full_unstemmed |
Impact of brine-induced stratification on the glacial carbon cycle |
title_sort |
impact of brine-induced stratification on the glacial carbon cycle |
publishDate |
2018 |
url |
https://doi.org/10.5194/cp-6-575-2010 https://cp.copernicus.org/articles/6/575/2010/ |
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Sea ice |
genre_facet |
Sea ice |
op_source |
eISSN: 1814-9332 |
op_relation |
doi:10.5194/cp-6-575-2010 https://cp.copernicus.org/articles/6/575/2010/ |
op_doi |
https://doi.org/10.5194/cp-6-575-2010 |
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Climate of the Past |
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6 |
container_issue |
5 |
container_start_page |
575 |
op_container_end_page |
589 |
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1766195522796781568 |