Effects of eustatic sea-level change, ocean dynamics, and nutrient utilization on atmospheric pCO(2) and seawater composition over the last 130 000 years: a model study
We have developed and employed an Earth system model to explore the forcings of atmospheric pCO(2) change and the chemical and isotopic evolution of seawater over the last glacial cycle. Concentrations of dissolved phosphorus (DP), reactive nitrogen, molecular oxygen, dissolved inorganic carbon (DIC...
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Copernicus Gesellschaft Mbh
2016
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ftarchimer:oai:archimer.ifremer.fr:60800 2023-05-15T18:24:58+02:00 Effects of eustatic sea-level change, ocean dynamics, and nutrient utilization on atmospheric pCO(2) and seawater composition over the last 130 000 years: a model study Wallmann, K. Schneider, B. Sarnthein, M. 2016 application/pdf https://archimer.ifremer.fr/doc/00496/60800/64806.pdf https://archimer.ifremer.fr/doc/00496/60800/64807.pdf https://doi.org/10.5194/cp-12-339-2016 https://archimer.ifremer.fr/doc/00496/60800/ eng eng Copernicus Gesellschaft Mbh https://archimer.ifremer.fr/doc/00496/60800/64806.pdf https://archimer.ifremer.fr/doc/00496/60800/64807.pdf doi:10.5194/cp-12-339-2016 https://archimer.ifremer.fr/doc/00496/60800/ info:eu-repo/semantics/openAccess restricted use Climate Of The Past (1814-9324) (Copernicus Gesellschaft Mbh), 2016 , Vol. 12 , N. 2 , P. 339-375 text Publication info:eu-repo/semantics/article 2016 ftarchimer https://doi.org/10.5194/cp-12-339-2016 2021-09-23T20:32:46Z We have developed and employed an Earth system model to explore the forcings of atmospheric pCO(2) change and the chemical and isotopic evolution of seawater over the last glacial cycle. Concentrations of dissolved phosphorus (DP), reactive nitrogen, molecular oxygen, dissolved inorganic carbon (DIC), total alkalinity (TA), C-13-DIC, and C-14-DIC were calculated for 24 ocean boxes. The bi-directional water fluxes between these model boxes were derived from a 3-D circulation field of the modern ocean (Opa 8.2, NEMO) and tuned such that tracer distributions calculated by the box model were consistent with observational data from the modern ocean. To model the last 130 kyr, we employed records of past changes in sea-level, ocean circulation, and dust deposition. According to the model, about half of the glacial pCO(2) drawdown may be attributed to marine regressions. The glacial sea-level low-stands implied steepened ocean margins, a reduced burial of particulate organic carbon, phosphorus, and neritic carbonate at the margin seafloor, a decline in benthic denitrification, and enhanced weathering of emerged shelf sediments. In turn, low-stands led to a distinct rise in the standing stocks of DIC, TA, and nutrients in the global ocean, promoted the glacial sequestration of atmospheric CO2 in the ocean, and added C-13- and C-14-depleted DIC to the ocean as recorded in benthic foraminifera signals. The other half of the glacial drop in pCO(2) was linked to inferred shoaling of Atlantic meridional overturning circulation and more efficient utilization of nutrients in the Southern Ocean. The diminished ventilation of deep water in the glacial Atlantic and Southern Ocean led to significant C-14 depletions with respect to the atmosphere. According to our model, the deglacial rapid and stepwise rise in atmospheric pCO(2) was induced by upwelling both in the Southern Ocean and subarctic North Pacific and promoted by a drop in nutrient utilization in the Southern Ocean. The deglacial sea-level rise led to a gradual decline in nutrient, DIC, and TA stocks, a slow change due to the large size and extended residence times of dissolved chemical species in the ocean. Thus, the rapid deglacial rise in pCO(2) can be explained by fast changes in ocean dynamics and nutrient utilization whereas the gradual pCO(2) rise over the Holocene may be linked to the slow drop in nutrient and TA stocks that continued to promote an ongoing CO2 transfer from the ocean into the atmosphere. Article in Journal/Newspaper Southern Ocean Subarctic Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) Pacific Southern Ocean Climate of the Past 12 2 339 375 |
institution |
Open Polar |
collection |
Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) |
op_collection_id |
ftarchimer |
language |
English |
description |
We have developed and employed an Earth system model to explore the forcings of atmospheric pCO(2) change and the chemical and isotopic evolution of seawater over the last glacial cycle. Concentrations of dissolved phosphorus (DP), reactive nitrogen, molecular oxygen, dissolved inorganic carbon (DIC), total alkalinity (TA), C-13-DIC, and C-14-DIC were calculated for 24 ocean boxes. The bi-directional water fluxes between these model boxes were derived from a 3-D circulation field of the modern ocean (Opa 8.2, NEMO) and tuned such that tracer distributions calculated by the box model were consistent with observational data from the modern ocean. To model the last 130 kyr, we employed records of past changes in sea-level, ocean circulation, and dust deposition. According to the model, about half of the glacial pCO(2) drawdown may be attributed to marine regressions. The glacial sea-level low-stands implied steepened ocean margins, a reduced burial of particulate organic carbon, phosphorus, and neritic carbonate at the margin seafloor, a decline in benthic denitrification, and enhanced weathering of emerged shelf sediments. In turn, low-stands led to a distinct rise in the standing stocks of DIC, TA, and nutrients in the global ocean, promoted the glacial sequestration of atmospheric CO2 in the ocean, and added C-13- and C-14-depleted DIC to the ocean as recorded in benthic foraminifera signals. The other half of the glacial drop in pCO(2) was linked to inferred shoaling of Atlantic meridional overturning circulation and more efficient utilization of nutrients in the Southern Ocean. The diminished ventilation of deep water in the glacial Atlantic and Southern Ocean led to significant C-14 depletions with respect to the atmosphere. According to our model, the deglacial rapid and stepwise rise in atmospheric pCO(2) was induced by upwelling both in the Southern Ocean and subarctic North Pacific and promoted by a drop in nutrient utilization in the Southern Ocean. The deglacial sea-level rise led to a gradual decline in nutrient, DIC, and TA stocks, a slow change due to the large size and extended residence times of dissolved chemical species in the ocean. Thus, the rapid deglacial rise in pCO(2) can be explained by fast changes in ocean dynamics and nutrient utilization whereas the gradual pCO(2) rise over the Holocene may be linked to the slow drop in nutrient and TA stocks that continued to promote an ongoing CO2 transfer from the ocean into the atmosphere. |
format |
Article in Journal/Newspaper |
author |
Wallmann, K. Schneider, B. Sarnthein, M. |
spellingShingle |
Wallmann, K. Schneider, B. Sarnthein, M. Effects of eustatic sea-level change, ocean dynamics, and nutrient utilization on atmospheric pCO(2) and seawater composition over the last 130 000 years: a model study |
author_facet |
Wallmann, K. Schneider, B. Sarnthein, M. |
author_sort |
Wallmann, K. |
title |
Effects of eustatic sea-level change, ocean dynamics, and nutrient utilization on atmospheric pCO(2) and seawater composition over the last 130 000 years: a model study |
title_short |
Effects of eustatic sea-level change, ocean dynamics, and nutrient utilization on atmospheric pCO(2) and seawater composition over the last 130 000 years: a model study |
title_full |
Effects of eustatic sea-level change, ocean dynamics, and nutrient utilization on atmospheric pCO(2) and seawater composition over the last 130 000 years: a model study |
title_fullStr |
Effects of eustatic sea-level change, ocean dynamics, and nutrient utilization on atmospheric pCO(2) and seawater composition over the last 130 000 years: a model study |
title_full_unstemmed |
Effects of eustatic sea-level change, ocean dynamics, and nutrient utilization on atmospheric pCO(2) and seawater composition over the last 130 000 years: a model study |
title_sort |
effects of eustatic sea-level change, ocean dynamics, and nutrient utilization on atmospheric pco(2) and seawater composition over the last 130 000 years: a model study |
publisher |
Copernicus Gesellschaft Mbh |
publishDate |
2016 |
url |
https://archimer.ifremer.fr/doc/00496/60800/64806.pdf https://archimer.ifremer.fr/doc/00496/60800/64807.pdf https://doi.org/10.5194/cp-12-339-2016 https://archimer.ifremer.fr/doc/00496/60800/ |
geographic |
Pacific Southern Ocean |
geographic_facet |
Pacific Southern Ocean |
genre |
Southern Ocean Subarctic |
genre_facet |
Southern Ocean Subarctic |
op_source |
Climate Of The Past (1814-9324) (Copernicus Gesellschaft Mbh), 2016 , Vol. 12 , N. 2 , P. 339-375 |
op_relation |
https://archimer.ifremer.fr/doc/00496/60800/64806.pdf https://archimer.ifremer.fr/doc/00496/60800/64807.pdf doi:10.5194/cp-12-339-2016 https://archimer.ifremer.fr/doc/00496/60800/ |
op_rights |
info:eu-repo/semantics/openAccess restricted use |
op_doi |
https://doi.org/10.5194/cp-12-339-2016 |
container_title |
Climate of the Past |
container_volume |
12 |
container_issue |
2 |
container_start_page |
339 |
op_container_end_page |
375 |
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