Basin bifurcations, oscillatory instability and rate-induced thresholds for Atlantic meridional overturning circulation in a global oceanic box model

Alkhayuon, Hassan; Ashwin, Peter; Jackson, Laura; Quinn, Courtney; Wood, Richard

doi:10.1098/rspa.2019.0051

Cited by 61 publications

(99 citation statements)

References 54 publications

(216 reference statements)

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“…Such scenarios will be considered in a future study. We note that even the present box model exhibits a range of rate-dependent and duration-dependent responses to rapid changes in fresh water forcing (Alkhayuon et al 2019).…”

Section: Discussionmentioning

confidence: 75%

“…Our model adopts a similar broad approach to the box model of Rahmstorf (1996) (Alkhayuon et al 2019).…”

Section: The Box Modelmentioning

confidence: 99%

“…This was shown in H11, which demonstrated that the region of bistable equilibrium solutions in FAMOUS A is narrower than the hysteresis region that appears in response to the slow increase then decrease of H. However in what follows we adopt a pragmatic definition of the 'AMOC threshold' as the value H crit of the additional freshwater flux H when the AMOC strength first reaches zero in the 'ramp-up' phase of the experiment (see dashed lines in Figure 3c). Further discussion of the response of the box model to time-varying H, including rate-dependent tipping responses, can be found in Alkhayuon et al (2019).…”

Section: Dynamics Of the Hysteresismentioning

confidence: 99%

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Observable, low-order dynamical controls on thresholds of the Atlantic meridional overturning circulation

et al. 2019

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We examine the dynamics of thresholds of the Atlantic Meridional Overturning Circulation (AMOC) in an Atmosphere-Ocean General Circulation Model (AOGCM) and a simple box model. We show that AMOC thresholds in the AOGCM are controlled by low-order dynamics encapsulated in the box model. In both models, AMOC collapse is primarily initiated by the development of a strong salinity advection feedback in the North Atlantic. The box model parameters are potentially observable properties of the unperturbed (present day) ocean state, and when calibrated to a range of AOGCM states predict (within some error bars) the critical rate of fresh water input (H crit) needed to turn off the AMOC in the AOGCM. In contrast, the meridional fresh water transport by the MOC (M OV , a widely-used diagnostic of AMOC bi-stability) on its own is a poor predictor of H crit. When the AOGCM is run with increased atmospheric carbon dioxide, H crit increases. We use the dynamical understanding from the box model to show that this increase is due partly to intensification of the global hydrological cycle and heat penetration into the near-surface ocean, both robust features of climate change projections. However changes in the gyre fresh water transport efficiency (a less robustly modelled process) are also important.

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Section: Discussionmentioning

confidence: 75%

“…Our model adopts a similar broad approach to the box model of Rahmstorf (1996) (Alkhayuon et al 2019).…”

Section: The Box Modelmentioning

confidence: 99%

Section: Dynamics Of the Hysteresismentioning

confidence: 99%

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Observable, low-order dynamical controls on thresholds of the Atlantic meridional overturning circulation

et al. 2019

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“…Ocean models, ranging from simple box models to complex general circulation models, have informed our understanding of the mechanisms that drive the AMOC and its variability (e.g., Bingham et al, ; Böning et al, ; Robson et al, ). Box models with analytical or numerical solutions (e.g., Stommel, ; Marotzke et al, 1988; Griffies & Tziperman, ; Longworth et al, ; Wood et al, ; Alkhayuon et al, ) were and still are useful (and popular) tools to illustrate and study possible AMOC behavior. Within their limitations (spatial resolution, physical assumptions, parameterisation choice, etc.)…”

Section: Introductionmentioning

confidence: 99%

The Atlantic Meridional Overturning Circulation in High‐Resolution Models

et al. 2020

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The Atlantic meridional overturning circulation (AMOC) represents the zonally integrated stream function of meridional volume transport in the Atlantic Basin. The AMOC plays an important role in transporting heat meridionally in the climate system. Observations suggest a heat transport by the AMOC of 1.3 PW at 26°N-a latitude which is close to where the Atlantic northward heat transport is thought to reach its maximum. This shapes the climate of the North Atlantic region as we know it today. In recent years there has been significant progress both in our ability to observe the AMOC in nature and to simulate it in numerical models. Most previous modeling investigations of the AMOC and its impact on climate have relied on models with horizontal resolution that does not resolve ocean mesoscale eddies and the dynamics of the Gulf Stream/North Atlantic Current system. As a result of recent increases in computing power, models are now being run that are able to represent mesoscale ocean dynamics and the circulation features that rely on them. The aim of this review is to describe new insights into the AMOC provided by high-resolution models. Furthermore, we will describe how high-resolution model simulations can help resolve outstanding challenges in our understanding of the AMOC. Key Points:• Observations and high-resolution models have changed view on the AMOC pathways • High-resolution models suggest the presence of previously unknown high-frequency AMOC variability • High-resolution models allow to estimate the intrinsic/chaotic component of the AMOCCorrespondence to:

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“…In the studies of atmospheric, oceanic, and coupled variability of the climate system, considerable progress has been made in applying dynamical systems theory and, in particular, bifurcation theory to models subject to time-dependent forcing (Alkhayuon et al, 2019) or to models that lie further towards the high end (Rahmstorf et al, 2005;Hawkins et al, 2011) of the model hierarchy originally proposed by Schneider and Dickinson (1974). More recently, Ghil (2001) and Held (2005), among others, have emphasized the need to pursue such a hierarchy systematically in order to further increase understanding of the climate system and of its pre-dictability, rather than merely pushing it to higher and higher resolutions in order to achieve ever more detailed simulations of the system's behavior for a limited set of semiempirical parameter values.…”

Section: Problem 3: Oceanic Interannual Variabilitymentioning

confidence: 99%

Review article: Hilbert problems for the climate sciences in the 21st century – 20 years later

Ghil

2020

Nonlin. Processes Geophys.

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Abstract. The scientific problems posed by the Earth's atmosphere, oceans, cryosphere – along with the land surface and biota that interact with them – are central to major socioeconomic and political concerns in the 21st century. It is natural, therefore, that a certain impatience should prevail in attempting to solve these problems. The point of a review paper published in this journal in 2001 was that one should proceed with all diligence but not excessive haste, namely “festina lente”, i.e., “to hurry in a measured way”. The earlier paper traced the necessary progress through the solutions of 10 problems, starting with “What can we predict beyond 1 week, for how long, and by what methods?” and ending with “Can we achieve enlightened climate control of our planet by the end of the century?” A unified framework was proposed to deal with these problems in succession, from the shortest to the longest timescale, i.e., from weeks to centuries and millennia. The framework is that of dynamical systems theory, with an emphasis on successive bifurcations and the ergodic theory of nonlinear systems, on the one hand, and on pursuing this approach across a hierarchy of climate models, from the simplest, highly idealized ones to the most detailed ones. Here, we revisit some of these problems, 20 years later,1 and extend the framework to coupled climate–economy modeling.

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Basin bifurcations, oscillatory instability and rate-induced thresholds for Atlantic meridional overturning circulation in a global oceanic box model

Cited by 61 publications

References 54 publications

Observable, low-order dynamical controls on thresholds of the Atlantic meridional overturning circulation

Observable, low-order dynamical controls on thresholds of the Atlantic meridional overturning circulation

The Atlantic Meridional Overturning Circulation in High‐Resolution Models

Review article: Hilbert problems for the climate sciences in the 21st century – 20 years later

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