North Atlantic Ocean Internal Decadal Variability: Role of the Mean State and Ocean‐Atmosphere Coupling

Gastineau, Guillaume; Mignot, Juliette; Arzel, Olivier; Huck, Thierry

doi:10.1029/2018jc014074

Cited by 24 publications

(36 citation statements)

References 66 publications

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“…This low-frequency variability in the MOC is consistent with several other ocean hindcast studies (e.g., Biastoch et al 2008;Robson et al 2012;Danabasoglu et al 2016). Such a MOC variability with ;20-yr periodicity may be intrinsic ocean only mode related to deep-water formation at high latitudes (e.g., Kwon and Frankignoul 2014), which can be intensified by the atmospheric forcing (Gastineau et al 2018). We note that these low-frequency MOC changes are beyond the scope of this paper because of the limited length of model data used.…”

Section: Moc and Its Variabilitymentioning

confidence: 90%

Local and Downstream Relationships between Labrador Sea Water Volume and North Atlantic Meridional Overturning Circulation Variability

Lozier

Danabasoglu

et al. 2019

Journal of Climate

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While it has generally been understood that the production of Labrador Sea Water (LSW) impacts the Atlantic meridional overturning circulation (MOC), this relationship has not been explored extensively or validated against observations. To explore this relationship, a suite of global ocean–sea ice models forced by the same interannually varying atmospheric dataset, varying in resolution from non-eddy-permitting to eddy-permitting (1°–1/4°), is analyzed to investigate the local and downstream relationships between LSW formation and the MOC on interannual to decadal time scales. While all models display a strong relationship between changes in the LSW volume and the MOC in the Labrador Sea, this relationship degrades considerably downstream of the Labrador Sea. In particular, there is no consistent pattern among the models in the North Atlantic subtropical basin over interannual to decadal time scales. Furthermore, the strong response of the MOC in the Labrador Sea to LSW volume changes in that basin may be biased by the overproduction of LSW in many models compared to observations. This analysis shows that changes in LSW volume in the Labrador Sea cannot be clearly and consistently linked to a coherent MOC response across latitudes over interannual to decadal time scales in ocean hindcast simulations of the last half century. Similarly, no coherent relationships are identified between the MOC and the Labrador Sea mixed layer depth or the density of newly formed LSW across latitudes or across models over interannual to decadal time scales.

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Section: Moc and Its Variabilitymentioning

confidence: 90%

Local and Downstream Relationships between Labrador Sea Water Volume and North Atlantic Meridional Overturning Circulation Variability

Lozier

Danabasoglu

et al. 2019

Journal of Climate

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“…Such a warmer mean state modifies the subpolar gyre currents and the subsurface stratification in the Eastern Atlantic Ocean where the mixed layer is deepest in IPSL-CM5A models. These changes were suggested to explain a smaller growth of baroclinic instabilities triggering the propagation of westward propagating anomalies (Gastineau et al, 2018). It is therefore likely that the different tuning of IPSL-CM5A2 led to similar changes.…”

Section: Ocean Variabilitymentioning

confidence: 96%

“…This difference can be explained by the different tuning of the two model versions. Gastineau et al (2018) used IPSL-CM5A-MR, a variant of IPSL-CM5A with an improved horizontal resolution in the atmosphere (2.5°× 1.25°vs 3.75°× 1.87°), and also found that a warmer mean state led to a reduction of the 20-yr variability https://doi.org/10.5194/gmd-2019-332 Preprint. Discussion started: 9 December 2019 c Author(s) 2019.…”

Section: Ocean Variabilitymentioning

confidence: 99%

IPSL-CM5A2. An Earth System Model designed for multi-millennial climate simulations

Sepulchre¹,

Caubel²,

Ladant³

et al. 2019

Preprint

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Abstract. Based on the CMIP5-generation previous IPSL earth system model, we designed a new version, IPSL-CM5A2, aiming at running multi-millennial simulations typical of deep-time paleoclimates studies. Three priorities were followed during the set-up of the model: (1) improving the overall model computing performance, (2) overcoming a persistent cold bias depicted in the previous model generation, and (3) making the model able to handle the specific continental configurations of the geological past. Technical developments have been performed on separate components and on the coupling system to speed up the whole coupled model. These developments include the integration of hybrid parallelization MPI-OpenMP in LMDz atmospheric component, the use of a new library to perform parallel asynchronous input/output by using computing cores as “IO servers”, the use of a parallel coupling library between the ocean and the atmospheric components. The model can now simulate ~100 years per day, opening new possibilities towards the production of multi-millennial simulations with a full earth system model. The tuning strategy employed to overcome a persistent cold bias is detailed. The confrontation of an historical simulation to climatological observations shows overall improved ocean meridional overturning circulation, marine productivity and latitudinal position of zonal wind patterns. We also present the numerous steps required to run the IPSL-CM5A2 for deep-time paleoclimates through a preliminary case-study for the Cretaceous. Namely, a specific work on the ocean model grid was required to run the model for specific continental configurations in which continents are relocated according to past paleogeographic reconstructions. By briefly discussing the spin-up of such a simulation, we elaborate on the requirements and challenges awaiting paleoclimate modelling in the next years, namely finding the best trade-off between the level of description of the processes and the computing cost on supercomputers.

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“…-Earth system models of intermediate complexity (Claussen et al, 2002), with coarse spatial resolution and simplifications in the physics, allow very efficient computation times and have been used extensively to explore Quaternary paleoclimates and run transient simulations (Roberts et al, 2014;Caley et al, 2014). As an example, the iLOVECLIM model (Goosse et al, 2010;Roche, 2013) provides more than 2500 simulated years per day (hereafter SYPD) on one computing core at a ∼ 5.6 • spatial resolution (three vertical levels) in the atmosphere and a full ocean general circulation model (OGCM) at 3 • × 3 • (21 vertical levels) with two tracers. Performance is still 850 SYPD with 20 tracers in the ocean (Bouttes et al, 2015b;Missiaen et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

IPSL-CM5A2 – an Earth system model designed for multi-millennial climate simulations

et al. 2020

Self Cite

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Abstract. Based on the fifth phase of the Coupled Model Intercomparison Project (CMIP5)-generation previous Institut Pierre Simon Laplace (IPSL) Earth system model, we designed a new version, IPSL-CM5A2, aiming at running multi-millennial simulations typical of deep-time paleoclimate studies. Three priorities were followed during the setup of the model: (1) improving the overall model computing performance, (2) overcoming a persistent cold bias depicted in the previous model generation and (3) making the model able to handle the specific continental configurations of the geological past. These developments include the integration of hybrid parallelization Message Passing Interface – Open Multi-Processing (MPI-OpenMP) in the atmospheric model of the Laboratoire de Météorologie Dynamique (LMDZ), the use of a new library to perform parallel asynchronous input/output by using computing cores as “I/O servers” and the use of a parallel coupling library between the ocean and the atmospheric components. The model, which runs with an atmospheric resolution of 3.75∘×1.875∘ and 2 to 0.5∘ in the ocean, can now simulate ∼100 years per day, opening new possibilities towards the production of multi-millennial simulations with a full Earth system model. The tuning strategy employed to overcome a persistent cold bias is detailed. The confrontation of a historical simulation to climatological observations shows overall improved ocean meridional overturning circulation, marine productivity and latitudinal position of zonal wind patterns. We also present the numerous steps required to run IPSL-CM5A2 for deep-time paleoclimates through a preliminary case study for the Cretaceous. Namely, specific work on the ocean model grid was required to run the model for specific continental configurations in which continents are relocated according to past paleogeographic reconstructions. By briefly discussing the spin-up of such a simulation, we elaborate on the requirements and challenges awaiting paleoclimate modeling in the next years, namely finding the best trade-off between the level of description of the processes and the computing cost on supercomputers.

show abstract

North Atlantic Ocean Internal Decadal Variability: Role of the Mean State and Ocean‐Atmosphere Coupling

Cited by 24 publications

References 66 publications

Local and Downstream Relationships between Labrador Sea Water Volume and North Atlantic Meridional Overturning Circulation Variability

Local and Downstream Relationships between Labrador Sea Water Volume and North Atlantic Meridional Overturning Circulation Variability

IPSL-CM5A2. An Earth System Model designed for multi-millennial climate simulations

IPSL-CM5A2 – an Earth system model designed for multi-millennial climate simulations

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