Ocean carbon cycle feedbacks in CMIP6 models: contributions from different basins

The ocean response to carbon emissions involves the combined effect of an increase in atmospheric CO 2 , acting to enhance the ocean carbon storage, and climate change, acting to decrease the ocean carbon storage. This ocean response can be characterised in terms of a carbon–concentration feedback a...

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Published in:Biogeosciences
Main Authors: Katavouta, Anna, Williams, Richard G.
Format: Text
Language:English
Published: 2021
Subjects:
Online Access:https://doi.org/10.5194/bg-18-3189-2021
https://bg.copernicus.org/articles/18/3189/2021/
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spelling ftcopernicus:oai:publications.copernicus.org:bg92016 2023-05-15T14:59:09+02:00 Ocean carbon cycle feedbacks in CMIP6 models: contributions from different basins Katavouta, Anna Williams, Richard G. 2021-05-27 application/pdf https://doi.org/10.5194/bg-18-3189-2021 https://bg.copernicus.org/articles/18/3189/2021/ eng eng doi:10.5194/bg-18-3189-2021 https://bg.copernicus.org/articles/18/3189/2021/ eISSN: 1726-4189 Text 2021 ftcopernicus https://doi.org/10.5194/bg-18-3189-2021 2021-05-31T16:22:13Z The ocean response to carbon emissions involves the combined effect of an increase in atmospheric CO 2 , acting to enhance the ocean carbon storage, and climate change, acting to decrease the ocean carbon storage. This ocean response can be characterised in terms of a carbon–concentration feedback and a carbon–climate feedback. The contribution from different ocean basins to these feedbacks on centennial timescales is explored using diagnostics of ocean carbonate chemistry, physical ventilation and biological processes in 11 CMIP6 Earth system models. To gain mechanistic insight, the dependence of these feedbacks on the Atlantic Meridional Overturning Circulation (AMOC) is also investigated in an idealised climate model and the CMIP6 models. For the carbon–concentration feedback, the Atlantic, Pacific and Southern oceans provide comparable contributions when estimated in terms of the volume-integrated carbon storage. This large contribution from the Atlantic Ocean relative to its size is due to strong local physical ventilation and an influx of carbon transported from the Southern Ocean. The Southern Ocean has large anthropogenic carbon uptake from the atmosphere, but its contribution to the carbon storage is relatively small due to large carbon transport to the other basins. For the carbon–climate feedback estimated in terms of carbon storage, the Atlantic and Arctic oceans provide the largest contributions relative to their size. In the Atlantic, this large contribution is primarily due to climate change acting to reduce the physical ventilation. In the Arctic, this large contribution is associated with a large warming per unit volume. The Southern Ocean provides a relatively small contribution to the carbon–climate feedback, due to competition between the climate effects of a decrease in solubility and physical ventilation and an increase in accumulation of regenerated carbon. The more poorly ventilated Indo-Pacific Ocean provides a small contribution to the carbon cycle feedbacks relative to its size. In the Atlantic Ocean, the carbon cycle feedbacks strongly depend on the AMOC strength and its weakening with warming. In the Arctic, there is a moderate correlation between the AMOC weakening and the carbon–climate feedback that is related to changes in carbonate chemistry. In the Pacific, Indian and Southern oceans, there is no clear correlation between the AMOC and the carbon cycle feedbacks, suggesting that other processes control the ocean ventilation and carbon storage there. Text Arctic Climate change Southern Ocean Copernicus Publications: E-Journals Arctic Indian Pacific Southern Ocean Biogeosciences 18 10 3189 3218
institution Open Polar
collection Copernicus Publications: E-Journals
op_collection_id ftcopernicus
language English
description The ocean response to carbon emissions involves the combined effect of an increase in atmospheric CO 2 , acting to enhance the ocean carbon storage, and climate change, acting to decrease the ocean carbon storage. This ocean response can be characterised in terms of a carbon–concentration feedback and a carbon–climate feedback. The contribution from different ocean basins to these feedbacks on centennial timescales is explored using diagnostics of ocean carbonate chemistry, physical ventilation and biological processes in 11 CMIP6 Earth system models. To gain mechanistic insight, the dependence of these feedbacks on the Atlantic Meridional Overturning Circulation (AMOC) is also investigated in an idealised climate model and the CMIP6 models. For the carbon–concentration feedback, the Atlantic, Pacific and Southern oceans provide comparable contributions when estimated in terms of the volume-integrated carbon storage. This large contribution from the Atlantic Ocean relative to its size is due to strong local physical ventilation and an influx of carbon transported from the Southern Ocean. The Southern Ocean has large anthropogenic carbon uptake from the atmosphere, but its contribution to the carbon storage is relatively small due to large carbon transport to the other basins. For the carbon–climate feedback estimated in terms of carbon storage, the Atlantic and Arctic oceans provide the largest contributions relative to their size. In the Atlantic, this large contribution is primarily due to climate change acting to reduce the physical ventilation. In the Arctic, this large contribution is associated with a large warming per unit volume. The Southern Ocean provides a relatively small contribution to the carbon–climate feedback, due to competition between the climate effects of a decrease in solubility and physical ventilation and an increase in accumulation of regenerated carbon. The more poorly ventilated Indo-Pacific Ocean provides a small contribution to the carbon cycle feedbacks relative to its size. In the Atlantic Ocean, the carbon cycle feedbacks strongly depend on the AMOC strength and its weakening with warming. In the Arctic, there is a moderate correlation between the AMOC weakening and the carbon–climate feedback that is related to changes in carbonate chemistry. In the Pacific, Indian and Southern oceans, there is no clear correlation between the AMOC and the carbon cycle feedbacks, suggesting that other processes control the ocean ventilation and carbon storage there.
format Text
author Katavouta, Anna
Williams, Richard G.
spellingShingle Katavouta, Anna
Williams, Richard G.
Ocean carbon cycle feedbacks in CMIP6 models: contributions from different basins
author_facet Katavouta, Anna
Williams, Richard G.
author_sort Katavouta, Anna
title Ocean carbon cycle feedbacks in CMIP6 models: contributions from different basins
title_short Ocean carbon cycle feedbacks in CMIP6 models: contributions from different basins
title_full Ocean carbon cycle feedbacks in CMIP6 models: contributions from different basins
title_fullStr Ocean carbon cycle feedbacks in CMIP6 models: contributions from different basins
title_full_unstemmed Ocean carbon cycle feedbacks in CMIP6 models: contributions from different basins
title_sort ocean carbon cycle feedbacks in cmip6 models: contributions from different basins
publishDate 2021
url https://doi.org/10.5194/bg-18-3189-2021
https://bg.copernicus.org/articles/18/3189/2021/
geographic Arctic
Indian
Pacific
Southern Ocean
geographic_facet Arctic
Indian
Pacific
Southern Ocean
genre Arctic
Climate change
Southern Ocean
genre_facet Arctic
Climate change
Southern Ocean
op_source eISSN: 1726-4189
op_relation doi:10.5194/bg-18-3189-2021
https://bg.copernicus.org/articles/18/3189/2021/
op_doi https://doi.org/10.5194/bg-18-3189-2021
container_title Biogeosciences
container_volume 18
container_issue 10
container_start_page 3189
op_container_end_page 3218
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