Initialisation and predictability of the AMOC over the last 50 years in a climate model
The mechanisms involved in Atlantic meridional overturning circulation (AMOC) decadal variability and predictability over the last 50 years are analysed in the IPSL-CM5A-LR model using historical and initialised simulations. The initialisation procedure only uses nudging towards sea surface temperat...
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ftird:oai:ird.fr:fdi:010060870 2024-09-09T19:38:46+00:00 Initialisation and predictability of the AMOC over the last 50 years in a climate model Presentation and analysis of the IPSL and CNRM climate models used in CMIP5 Swingedouw, D. /Mignot, Juliette Labetoulle, S. Guilyardi, E. Madec, G. OCEAN ATLANTIQUE ATLANTIQUE NORD 2013 https://www.documentation.ird.fr/hor/fdi:010060870 EN eng https://www.documentation.ird.fr/hor/fdi:010060870 oai:ird.fr:fdi:010060870 Swingedouw D., Mignot Juliette, Labetoulle S., Guilyardi E., Madec G. Initialisation and predictability of the AMOC over the last 50 years in a climate model. In : . Presentation and analysis of the IPSL and CNRM climate models used in CMIP5 2013, 40 (9-10), p. 2381-2399 Decadal climate prediction Ocean dynamics Atlantic meridional overturning circulation Hindcast Predictability Volcanic eruptions Mount Agung North Atlantic oscillation text 2013 ftird 2024-08-15T05:57:42Z The mechanisms involved in Atlantic meridional overturning circulation (AMOC) decadal variability and predictability over the last 50 years are analysed in the IPSL-CM5A-LR model using historical and initialised simulations. The initialisation procedure only uses nudging towards sea surface temperature anomalies with a physically based restoring coefficient. When compared to two independent AMOC reconstructions, both the historical and nudged ensemble simulations exhibit skill at reproducing AMOC variations from 1977 onwards, and in particular two maxima occurring respectively around 1978 and 1997. We argue that one source of skill is related to the large Mount Agung volcanic eruption starting in 1963, which reset an internal 20-year variability cycle in the North Atlantic in the model. This cycle involves the East Greenland Current intensity, and advection of active tracers along the subpolar gyre, which leads to an AMOC maximum around 15 years after the Mount Agung eruption. The 1997 maximum occurs approximately 20 years after the former one. The nudged simulations better reproduce this second maximum than the historical simulations. This is due to the initialisation of a cooling of the convection sites in the 1980s under the effect of a persistent North Atlantic oscillation (NAO) positive phase, a feature not captured in the historical simulations. Hence we argue that the 20-year cycle excited by the 1963 Mount Agung eruption together with the NAO forcing both contributed to the 1990s AMOC maximum. These results support the existence of a 20-year cycle in the North Atlantic in the observations. Hindcasts following the CMIP5 protocol are launched from a nudged simulation every 5 years for the 1960-2005 period. They exhibit significant correlation skill score as compared to an independent reconstruction of the AMOC from 4-year lead-time average. This encouraging result is accompanied by increased correlation skills in reproducing the observed 2-m air temperature in the bordering regions of the North Atlantic as ... Text East Greenland east greenland current Greenland North Atlantic North Atlantic oscillation IRD (Institute de recherche pour le développement): Horizon Greenland |
institution |
Open Polar |
collection |
IRD (Institute de recherche pour le développement): Horizon |
op_collection_id |
ftird |
language |
English |
topic |
Decadal climate prediction Ocean dynamics Atlantic meridional overturning circulation Hindcast Predictability Volcanic eruptions Mount Agung North Atlantic oscillation |
spellingShingle |
Decadal climate prediction Ocean dynamics Atlantic meridional overturning circulation Hindcast Predictability Volcanic eruptions Mount Agung North Atlantic oscillation Swingedouw, D. /Mignot, Juliette Labetoulle, S. Guilyardi, E. Madec, G. Initialisation and predictability of the AMOC over the last 50 years in a climate model |
topic_facet |
Decadal climate prediction Ocean dynamics Atlantic meridional overturning circulation Hindcast Predictability Volcanic eruptions Mount Agung North Atlantic oscillation |
description |
The mechanisms involved in Atlantic meridional overturning circulation (AMOC) decadal variability and predictability over the last 50 years are analysed in the IPSL-CM5A-LR model using historical and initialised simulations. The initialisation procedure only uses nudging towards sea surface temperature anomalies with a physically based restoring coefficient. When compared to two independent AMOC reconstructions, both the historical and nudged ensemble simulations exhibit skill at reproducing AMOC variations from 1977 onwards, and in particular two maxima occurring respectively around 1978 and 1997. We argue that one source of skill is related to the large Mount Agung volcanic eruption starting in 1963, which reset an internal 20-year variability cycle in the North Atlantic in the model. This cycle involves the East Greenland Current intensity, and advection of active tracers along the subpolar gyre, which leads to an AMOC maximum around 15 years after the Mount Agung eruption. The 1997 maximum occurs approximately 20 years after the former one. The nudged simulations better reproduce this second maximum than the historical simulations. This is due to the initialisation of a cooling of the convection sites in the 1980s under the effect of a persistent North Atlantic oscillation (NAO) positive phase, a feature not captured in the historical simulations. Hence we argue that the 20-year cycle excited by the 1963 Mount Agung eruption together with the NAO forcing both contributed to the 1990s AMOC maximum. These results support the existence of a 20-year cycle in the North Atlantic in the observations. Hindcasts following the CMIP5 protocol are launched from a nudged simulation every 5 years for the 1960-2005 period. They exhibit significant correlation skill score as compared to an independent reconstruction of the AMOC from 4-year lead-time average. This encouraging result is accompanied by increased correlation skills in reproducing the observed 2-m air temperature in the bordering regions of the North Atlantic as ... |
format |
Text |
author |
Swingedouw, D. /Mignot, Juliette Labetoulle, S. Guilyardi, E. Madec, G. |
author_facet |
Swingedouw, D. /Mignot, Juliette Labetoulle, S. Guilyardi, E. Madec, G. |
author_sort |
Swingedouw, D. |
title |
Initialisation and predictability of the AMOC over the last 50 years in a climate model |
title_short |
Initialisation and predictability of the AMOC over the last 50 years in a climate model |
title_full |
Initialisation and predictability of the AMOC over the last 50 years in a climate model |
title_fullStr |
Initialisation and predictability of the AMOC over the last 50 years in a climate model |
title_full_unstemmed |
Initialisation and predictability of the AMOC over the last 50 years in a climate model |
title_sort |
initialisation and predictability of the amoc over the last 50 years in a climate model |
publishDate |
2013 |
url |
https://www.documentation.ird.fr/hor/fdi:010060870 |
op_coverage |
OCEAN ATLANTIQUE ATLANTIQUE NORD |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
East Greenland east greenland current Greenland North Atlantic North Atlantic oscillation |
genre_facet |
East Greenland east greenland current Greenland North Atlantic North Atlantic oscillation |
op_relation |
https://www.documentation.ird.fr/hor/fdi:010060870 oai:ird.fr:fdi:010060870 Swingedouw D., Mignot Juliette, Labetoulle S., Guilyardi E., Madec G. Initialisation and predictability of the AMOC over the last 50 years in a climate model. In : . Presentation and analysis of the IPSL and CNRM climate models used in CMIP5 2013, 40 (9-10), p. 2381-2399 |
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1809907676542402560 |