On the Relative Roles of the Atmosphere and Ocean in the Atlantic Multidecadal Variability

Garuba, O. A.; Lu, Jian; Singh, H. A.; Liu, Fukai; Rasch, P.

doi:10.1029/2018gl078882

Cited by 20 publications

(23 citation statements)

References 33 publications

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“…This argument is based on analyses of coupled general circulation model (CGCM) simulations with passive (slab) ocean models. This hypothesis runs counter to an extensive body of literature extending back decades that consistently relates simulated AMV to an AMOC precursor (e.g., Delworth et al, ), and it has been rebutted by several recent studies (Delworth et al, ; Garuba et al, ; O'Reilly et al, ; Wills et al, ; R. Zhang, ; R. Zhang et al, ) that argue that stochastic atmospheric forcing alone does not offer a mechanistic explanation of AMV that is consistent with that found in more realistic CGCM simulations with active ocean models.…”

Section: Introductionmentioning

confidence: 71%

“…The above results suggest a role for internal variability in recent AMV transitions, but they do not necessarily imply a more dominant role for ocean dynamics than intrinsic atmospheric variability (Clement et al, ). Some previous studies have focused on surface turbulent heat fluxes ( Q se ) for the telltale signature of ocean‐driven NASST variations (Garuba et al, ; Gulev et al, ; O'Reilly et al, ; Wills et al, ; R. Zhang et al, ). On decadal‐multidecadal timescales, heat is released to (taken from) the atmosphere through Q se when SST is anomalously warm (cold) due to heat convergence (divergence) by ocean dynamics.…”

Section: Resultsmentioning

confidence: 99%

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Key Role of Internal Ocean Dynamics in Atlantic Multidecadal Variability During the Last Half Century

Kim

Yeager

Danabasoglu

2018

Geophysical Research Letters

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This study presents multiple lines of evidence from observations and model simulations that support a key role for ocean dynamics, rather than external forcings, in Atlantic multidecadal variability (AMV) during the last half century. Observed AMV fingerprints considered here include the low‐frequency spatiotemporal evolution of sea surface temperature, surface heat fluxes, and deep ocean hydrography. While largely absent in the forced response of a large ensemble historical simulations (LENSs), these fingerprints are clearly discernible in a long control simulation where the variability is purely internal. Further evidence derives from initialized decadal prediction simulations, which exhibit much higher skill at predicting the observed AMV of the past 50 years than LENS. The high correlation between the observed AMV and the externally forced version derived from LENS, which has been invoked as evidence for externally driven AMV, is shown to be largely an artifact of concurrent warming since the 1990s.

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Section: Introductionmentioning

confidence: 71%

Section: Resultsmentioning

confidence: 99%

Key Role of Internal Ocean Dynamics in Atlantic Multidecadal Variability During the Last Half Century

Kim

Yeager

Danabasoglu

2018

Geophysical Research Letters

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“…Slab models can therefore produce unrealistic surface flux anomalies and an overestimation of the upper ocean heat content change. This lack of realistic damping of upper ocean heat content by ocean circulation variations has lead to an attribution of the Atlantic multidecadal variability to atmospheric noise using slab simulations, but using the partial coupling approach here, we show that the multidecadal variability is most likely driven by ocean circulation changes in fully coupled simulations (Clement et al., 2015; Garuba, Lu, Singh, et al., 2018; Zhang, 2017). Avoiding the double counting of the roles of the atmosphere and ocean, our decomposition indicates that the fully coupled responses (surface flux components and ocean circulation responses) are indeed linear.…”

Section: Summary and Discussionmentioning

confidence: 74%

A Partial Coupling Method to Isolate the Roles of the Atmosphere and Ocean in Coupled Climate Simulations

Garuba

Rasch

2020

J Adv Model Earth Syst

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This study describes the formulation and application of a partial coupling method that disentangles the coupling between the atmosphere and ocean and isolates the atmosphere‐ and ocean‐driven components of the coupled climate interactions. In contrast to strategies using stand‐alone simulations with prescribed atmosphere or ocean states, the climate components in the partially coupled method remain coupled, but the impact of ocean circulation changes is removed from the air‐sea interaction using temperature‐like tracers. The partially coupled simulation thereby suppresses the ocean‐driven interaction and isolates an atmosphere‐driven interaction only. The ocean‐driven component can be inferred by comparing climate response in the partially coupled simulation with that of a standard fully coupled one. The partial coupling approach is applied to decompose the fully coupled climate response to CO2 quadrupling into atmosphere‐ and ocean‐driven components. The linearity of the decomposition is validated by simulating the ocean‐driven response using another complimentary partially coupled simulation forced only with the atmosphere‐driven anomalous surface fluxes. A comparison of the two partially coupled simulations with the fully coupled simulation indicates that the sum of the atmosphere‐ and ocean‐driven components accurately describes the fully coupled response. The decomposition identifies several robust atmosphere‐ and ocean‐driven features of the global warming and provides new insights into the impacts of atmospheric feedbacks on the Atlantic overturning circulation and sea ice response to CO2 increase.

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“…Related studies suggested that AMO is an inner variability of climate system, which can affect regional-to-hemispheric climate (Zhang, 2007;Knight et al, 2006). The slow variation of the Atlantic meridional overturning circulation (AMOC) is found to play a dominant role in the Atlantic multidecadal variability of SST (Zhang, 2017;Delworth et al, 2000;Garuba et al, 2018). In this study, AMO is defined as the detrended area-weighted average SST over the North Atlantic from 0° to 70°N during 1856-2018 based on the Kaplan SST dataset (Enfield et al, 2001).…”

Section: Amomentioning

confidence: 99%

On the interconnections among major climate modes and their common driving factors

Pan¹,

Wang²,

Yang³

et al. 2019

Preprint

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Abstract. The variations in oceanic and atmospheric modes on various timescales play important roles in generating regional and global climate variability. Many efforts have been devoted to identify the relationships between the variations in climate modes and regional climate variability, but rarely explored the interconnections among these climate modes. Here we use climate indices to represent the variations in major climate modes and we examine the harmonic relationship among the driving forces of climate modes by the combination of Slow Feature Analysis (SFA) and wavelet analysis. We find that all of the significant peak-periods of driving-force signals in the climate indices can be represented as the harmonics of four base periods: 2.32 yr, 3.90 yr, 6.55 yr and 11.02 yr. We infer that the period of 2.32 yr is associated with the signal of Quasi Biennial Oscillation (QBO). The periods of 3.90 yr and 6.55 yr are connected with the intrinsic variability of El Niño-Southern Oscillation (ENSO), and the period of 11.02 yr arises from the sunspot cycle. Results suggest that the base periods and their harmonic oscillations linked to QBO, ENSO and solar activities act as the key connections among the climatic modes with synchronous behaviors, highlighting the important roles of these three oscillations in the variability of current climate.

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On the Relative Roles of the Atmosphere and Ocean in the Atlantic Multidecadal Variability

Cited by 20 publications

References 33 publications

Key Role of Internal Ocean Dynamics in Atlantic Multidecadal Variability During the Last Half Century

Key Role of Internal Ocean Dynamics in Atlantic Multidecadal Variability During the Last Half Century

A Partial Coupling Method to Isolate the Roles of the Atmosphere and Ocean in Coupled Climate Simulations

On the interconnections among major climate modes and their common driving factors

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