Numerical bifurcation methods applied to climate models: analysis beyond simulation

Dijkstra, Henk A.

doi:10.5194/npg-26-359-2019

Cited by 12 publications

(10 citation statements)

References 61 publications

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“…The recent changes in a range of surface variables that show a relationship between Atlantic multidecadal variability and AMOC are consistent with recent direct estimates of AMOC flow volumes (Sun et al, 2021). The stability of AMOC is very much a matter of debate, but simple and intermediate models produce abrupt phase transitions (Dijkstra, 2019;Johnson et al, 2019), while more complex models produce a wide range of responses, showing high sensitivity to the background state (Johnson et al, 2019).…”

Section: Atlantic Meridional Overturning Circulationsupporting

confidence: 78%

“…Complex systems organise at a range of scales that operate by different rules depending on scale, and may be governed by an overall organising principle. Small-world network behaviour is one example (Watts and Strogatz, 1998;Latora and Marchiori, 2001;Donges et al, 2009) and attractors in the climate system another (Nicolis and Nicolis, 1986;Dijkstra, 2019;Faranda et al, 2019). This is the first of two papers that looks at climate through a complex systems lens, exploring how it has evolved since the pre-industrial era.…”

Section: Introductionmentioning

confidence: 99%

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The Pacific Ocean heat engine

Jones

Ricketts

2021

Preprint

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Abstract. Historical warming forms a sequence of steady-state regimes punctuated by abrupt shifts. These changes are regulated by a heat engine spanning the tropical Pacific Ocean teleconnected to a broader climate network. The eastern-central Pacific maintains steady-state conditions, delivering heat to the Western Pacific warm pool. They form a heat pump with heat moving from the cold to the warm reservoir, sustained by kinetic energy. The two reservoirs exchange heat on a range of timescales, with oscillatory behaviour that intensifies under forcing. The heat engine is part of a network of oscillations and circulation interacting on a range of timescales. The process is self-regulating: steady-state regimes persist until they become unstable due to an over- or under-supply of heat for dissipation, shifting warmer or cooler to a new stable state. Pre-industrial climate was in free mode, characterised by a loosely-coupled ocean-atmosphere with limited circulation, moving into forced mode in the latter 20th century, characterised by tighter coupling and stronger circulation through the tropical Pacific with more active teleconnections globally. Continued forcing produces a stepladder-like pattern of warming. Most shifts coincide with phase changes in decadal oscillations, switching from slower to faster modes of dissipation. El Niño events combine with regime shifts to propagate heat from the oceans to land and from the tropics to higher latitudes. The most recent shift commenced in the warm pool in December 2012, ending the so-called hiatus (1997–2013), global mean surface temperatures warming abruptly by ~0.25 °C in 2014–15.

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Section: Atlantic Meridional Overturning Circulationsupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

The Pacific Ocean heat engine

Jones

Ricketts

2021

Preprint

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“…Similar issues accompany thermodynamic and dynamic approaches to understanding climate variability (Palmer, 2013;Wehrli et al, 2018;Ghil and Lucarini, 2020), and the role of entropy in the climate system (Ozawa et al, 2003;Kleidon, 2009;Nicolis and Nicolis, 2010;. Dijkstra (2019) summarises the challenges of dealing explicitly with emergence in model studies of complex system behaviour. Finding the appropriate level where specific phenomena emerge is vital.…”

Section: Model Underdeterminationmentioning

confidence: 99%

“…Recent examples include a review of power laws and scaling on climate variability (Franzke et al, 2020), bifurcation analysis looking at climate oscillations (Dijkstra, 2019), statistical mechanics of climate .…”

Section: Climate Approached As a Complex Dynamic Systemmentioning

confidence: 99%

“…Finding the appropriate level where specific phenomena emerge is vital. The climate system is rich in emergent structures yet the question as to why they are there is rarely asked (e.g., Clement et al, 2005;Dijkstra, 2019). Examples of robust emergent structures include regime shifts, ENSO, the tropical warm pools and the Atlantic Meridional Overturning Circulation (AMOC), discussed in the following section.…”

Section: Model Underdeterminationmentioning

confidence: 99%

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Climate as a complex, self-regulating system

Jones

Ricketts

2021

Preprint

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Abstract. This paper explores whether climate is complicated or complex by examining the performance of a heat engine in the tropical Pacific, the Pacific Ocean heat engine, which is linked to a teleconnected network of circulation and oscillations. Sustained radiative forcing is widely expected to produce gradual change but instead produces step-wise regime shifts. The engine is a heat pump with cold-to-hot circulation maintained by kinetic energy produced by the Coriolis Effect. It is a fundamental response of a coupled ocean-atmosphere system to asymmetric circulation. This paper surveys emergent behaviours in climate models linked to such shifts. It explores how well models represent the heat engine, compares regime changes in models and observations, and examines how geostrophic controls on meridional heat transport set critical boundary conditions. The results reinforce the description of climate as a self-regulating system governed by the principle of least action. Teleconnected steady-state regimes are physically-induced by the need to maintain boundary-limited dissipation rates between the hemispheres, the equator and the poles. A sufficient imbalance of energy at the planetary surface produces regime shifts that switch between slow and fast dissipation pathways. The strength of coupling measured via heat engine characteristics is weaker in models than in the observed climate, failing to distinguish clearly between free and forced modes. The capacity of the coupled ocean-atmosphere system to maintain homeostasis allows Earth’s climate to be classified physically rather than statistically, the basic unit of climate being the steady-state regime.

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Abrupt Climate Changes and Tipping Points

Lam

2023

Handbooks in Philosophy

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Numerical bifurcation methods applied to climate models: analysis beyond simulation

Cited by 12 publications

References 61 publications

The Pacific Ocean heat engine

The Pacific Ocean heat engine

Climate as a complex, self-regulating system

Abrupt Climate Changes and Tipping Points

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