Nonmonotonic response of primary production and export to changes in mixed-layer depth in the Southern Ocean
Ongoing and future changes in wind and temperature are predicted to alter upper ocean vertical mixing across the Southern Ocean. How these changes will affect primary production (PP) remains unclear as mixing influences the two controlling factors: light and iron. We used a large ensemble of 1-D-bio...
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ftird:oai:ird.fr:fdi:010075620 2024-09-15T18:37:01+00:00 Nonmonotonic response of primary production and export to changes in mixed-layer depth in the Southern Ocean Llort, J. /Levy, Marina Sallee, J. B. Tagliabue, A. 2019 https://www.documentation.ird.fr/hor/fdi:010075620 EN eng https://www.documentation.ird.fr/hor/fdi:010075620 oai:ird.fr:fdi:010075620 Llort J., Levy Marina, Sallee J. B., Tagliabue A. Nonmonotonic response of primary production and export to changes in mixed-layer depth in the Southern Ocean. 2019, 46 (6), p. 3368-3377 Southern Ocean carbon export phytoplankton primary production mixed-layer depth CMIP5 text 2019 ftird 2024-08-15T05:57:41Z Ongoing and future changes in wind and temperature are predicted to alter upper ocean vertical mixing across the Southern Ocean. How these changes will affect primary production (PP) remains unclear as mixing influences the two controlling factors: light and iron. We used a large ensemble of 1-D-biogeochemical model simulations to explore the impacts of changes in mixed-layer depths on PP in the Southern Ocean. In summer, shoaling mixed-layer depth always reduced depth-integrated PP, despite increasing production rates. In winter, shoaling mixed layers had a two-staged impact: for moderate shoaling PP increased as light conditions improved, but more pronounced shoaling decreased iron supply, which reduced PP. The fraction of PP exported below 100 m also presented a nonmonotonic behavior. This suggests a potential future shift from a situation where reduced winter mixing increases PP and export, to a situation where PP and export may collapse if the ML shoals above a threshold depth. Plain Language Summary In the Southern Ocean, atmospheric warming associated to climate change is altering the depth at which surface waters are stirred, the so-called mixed-layer depth. A change in the mixed-layer depth impacts the phytoplankton cells that inhabit it by altering their two main limiting factors: iron and light. However, the sign and magnitude of this impact are still not clear. In this work we used mathematical simulations to explain how changes in the seasonal mixed-layer depth modify the supply of iron and the amount of light, and how these changes impact phytoplankton activity. Our results show that mixed-layer depth changes in summer and in winter have different impacts. Reducing summer mixed-layer depth did not change the iron supply, but it reduced the volume of water where phytoplankton thrived. In winter, shallower mixed-layer depth altered iron and light but in opposed ways. At first, phytoplankton increased its activity as more light became available. However, a continued shallowing of the mixed-layer depth ... Text Southern Ocean IRD (Institute de recherche pour le développement): Horizon |
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Open Polar |
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IRD (Institute de recherche pour le développement): Horizon |
op_collection_id |
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language |
English |
topic |
Southern Ocean carbon export phytoplankton primary production mixed-layer depth CMIP5 |
spellingShingle |
Southern Ocean carbon export phytoplankton primary production mixed-layer depth CMIP5 Llort, J. /Levy, Marina Sallee, J. B. Tagliabue, A. Nonmonotonic response of primary production and export to changes in mixed-layer depth in the Southern Ocean |
topic_facet |
Southern Ocean carbon export phytoplankton primary production mixed-layer depth CMIP5 |
description |
Ongoing and future changes in wind and temperature are predicted to alter upper ocean vertical mixing across the Southern Ocean. How these changes will affect primary production (PP) remains unclear as mixing influences the two controlling factors: light and iron. We used a large ensemble of 1-D-biogeochemical model simulations to explore the impacts of changes in mixed-layer depths on PP in the Southern Ocean. In summer, shoaling mixed-layer depth always reduced depth-integrated PP, despite increasing production rates. In winter, shoaling mixed layers had a two-staged impact: for moderate shoaling PP increased as light conditions improved, but more pronounced shoaling decreased iron supply, which reduced PP. The fraction of PP exported below 100 m also presented a nonmonotonic behavior. This suggests a potential future shift from a situation where reduced winter mixing increases PP and export, to a situation where PP and export may collapse if the ML shoals above a threshold depth. Plain Language Summary In the Southern Ocean, atmospheric warming associated to climate change is altering the depth at which surface waters are stirred, the so-called mixed-layer depth. A change in the mixed-layer depth impacts the phytoplankton cells that inhabit it by altering their two main limiting factors: iron and light. However, the sign and magnitude of this impact are still not clear. In this work we used mathematical simulations to explain how changes in the seasonal mixed-layer depth modify the supply of iron and the amount of light, and how these changes impact phytoplankton activity. Our results show that mixed-layer depth changes in summer and in winter have different impacts. Reducing summer mixed-layer depth did not change the iron supply, but it reduced the volume of water where phytoplankton thrived. In winter, shallower mixed-layer depth altered iron and light but in opposed ways. At first, phytoplankton increased its activity as more light became available. However, a continued shallowing of the mixed-layer depth ... |
format |
Text |
author |
Llort, J. /Levy, Marina Sallee, J. B. Tagliabue, A. |
author_facet |
Llort, J. /Levy, Marina Sallee, J. B. Tagliabue, A. |
author_sort |
Llort, J. |
title |
Nonmonotonic response of primary production and export to changes in mixed-layer depth in the Southern Ocean |
title_short |
Nonmonotonic response of primary production and export to changes in mixed-layer depth in the Southern Ocean |
title_full |
Nonmonotonic response of primary production and export to changes in mixed-layer depth in the Southern Ocean |
title_fullStr |
Nonmonotonic response of primary production and export to changes in mixed-layer depth in the Southern Ocean |
title_full_unstemmed |
Nonmonotonic response of primary production and export to changes in mixed-layer depth in the Southern Ocean |
title_sort |
nonmonotonic response of primary production and export to changes in mixed-layer depth in the southern ocean |
publishDate |
2019 |
url |
https://www.documentation.ird.fr/hor/fdi:010075620 |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_relation |
https://www.documentation.ird.fr/hor/fdi:010075620 oai:ird.fr:fdi:010075620 Llort J., Levy Marina, Sallee J. B., Tagliabue A. Nonmonotonic response of primary production and export to changes in mixed-layer depth in the Southern Ocean. 2019, 46 (6), p. 3368-3377 |
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1810481111959076864 |