Simulating AMOC tipping driven by internal climate variability with a rare event algorithm

npj Climate and Atmospheric Science, Год журнала: 2024, Номер 7(1)

Опубликована: Янв. 29, 2024

Abstract This study investigates the possibility of Atlantic Meridional Overturning Circulation (AMOC) noise-induced tipping solely driven by internal climate variability without applying external forcing that alter radiative or North freshwater budget. We address this hypothesis a rare event algorithm to ensemble simulations present-day with an intermediate complexity model. The successfully identifies trajectories leading abrupt AMOC slowdowns, which are unprecedented in 2000-year control run. Part these weakened states lead collapsed state evidence recovery on multi-centennial time scales. temperature and Northern Hemisphere jet stream responses internally-induced slowdowns show strong similarities those found externally forced state-of-the-art models. slowdown seems be initially Ekman transport due westerly wind stress anomalies subsequently sustained complete collapse oceanic convection Labrador Sea. These results demonstrate transitions purely model simulation but theoretically possible. Additionally, algorithms tool valuable general interest points since they introduce collecting large number events cannot sampled using traditional approaches. opens identifying mechanisms driving complex systems little a-priori knowledge is available.

Язык: Английский

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Rate-induced tipping in ecosystems and climate: the role of unstable states, basin boundaries and transient dynamics

Nonlinear processes in geophysics, Год журнала: 2023, Номер 30(4), С. 481 - 502

Опубликована: Ноя. 3, 2023

Abstract. The climate system as well ecosystems might undergo relatively sudden qualitative changes in the dynamics when environmental parameters or external forcings vary due to anthropogenic influences. study of these changes, called tipping phenomena, requires development new methodological approaches that allow phenomena observed nature be modeled, analyzed and predicted, especially concerning crisis its consequences. Here we briefly review mechanisms classical investigate rate-dependent which occur non-autonomous systems characterized by multiple timescales more detail. We focus on mechanism rate-induced caused basin boundary crossings. unravel this transition analyze, particular, role such crossings a parameter drift induces saddle-node bifurcation attractors saddle points emerge, including their basins attraction. Furthermore, detectability those bifurcations monitoring single trajectories state space find depending rate drift, masked hidden, they can only detected if critical is crossed. This analysis reveals unstable states type are organizing centers global multistable need much attention future studies.

Язык: Английский

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Weakening of the Atlantic Meridional Overturning Circulation driven by subarctic freshening since the mid-twentieth century

Nature Geoscience, Год журнала: 2024, Номер unknown

Опубликована: Ноя. 18, 2024

Язык: Английский

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A multicentennial mode of North Atlantic climate variability throughout the Last Glacial Maximum

Science Advances, Год журнала: 2023, Номер 9(44)

Опубликована: Ноя. 1, 2023

Paleoclimate proxy records from the North Atlantic region reveal substantially greater multicentennial temperature variability during Last Glacial Maximum (LGM) compared to current interglacial. As there was no obvious change in external forcing, causes for increased remain unknown. Exploiting LGM simulations with a comprehensive coupled climate model along high-resolution records, we introduce an oscillatory mode of variability, which is associated moderate variations meridional overturning circulation and depends on large-scale salinity distribution. This self-sustained amplified by sea-ice feedbacks induces maximum surface subpolar region. Characterized distinct climatic imprint different dynamics, oscillation has be distinguished Dansgaard-Oeschger emerges only under full forcing. The potential modes emerge or disappear response changing forcing may have implications future change.

Язык: Английский

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Extremes of summer Arctic sea ice reduction investigated with a rare event algorithm

Climate Dynamics, Год журнала: 2024, Номер 62(6), С. 5219 - 5237

Опубликована: Апрель 4, 2024

Abstract Various studies identified possible drivers of extremes Arctic sea ice reduction, such as observed in the summers 2007 and 2012, including preconditioning, local feedback mechanisms, oceanic heat transport synoptic- large-scale atmospheric circulations. However, a robust quantitative statistical analysis reduction is hindered by small number events that can be sampled observations numerical simulations with computationally expensive climate models. Recent tackled problem sampling using rare event algorithms, i.e., computational techniques developed physics to reduce cost required sample simulations. Here we apply algorithm ensemble intermediate complexity coupled model PlaSim-LSG investigate extreme negative summer pan-Arctic area anomalies under pre-industrial greenhouse gas conditions. Owing algorithm, estimate return times orders magnitude larger than feasible direct sampling, compute statistically significant composite maps dynamical quantities conditional on occurrence these extremes. We find extremely low are associated preconditioning through winter ice-ocean state, enhanced downward longwave radiation due an anomalously moist warm spring atmosphere sensible fluxes during spring-summer transition. As consequence three processes, ice-albedo becomes active leads amplification pre-existing summer.

Язык: Английский

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Rate-induced tipping in ecosystems and climate: the role of unstable states, basin boundaries and transient dynamics

Опубликована: Март 28, 2023

Abstract. The climate system as well ecosystems might undergo relatively sudden qualitative changes in the dynamics when environmental parameters or external forcings vary due to anthropogenic influences. study of these changes, called tipping phenomena, requires development new methodological approaches that allow modeling, analyzing, and predicting observed phenomena nature, especially concerning crisis its consequences. Here we briefly review mechanisms classical investigate more detail rate-dependent which occur non-autonomous systems characterized by multiple timescales. We focus on mechanism rate-induced caused basin boundary crossings. unravel this transition analyze, particular, role such crossings a parameter drift induces saddle-node bifurcation attractors saddle points emerge, including their basins attraction. Furthermore, detectability those bifurcations monitoring single trajectories state space find depending rate drift, be masked hidden they can detected only if critical is crossed. This analysis reveals quasi-stationary multistable are organizing centers global need much attention future studies.

Язык: Английский

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AMOC Variability in Climate Models and Its Dependence on the Mean State

Geophysical Research Letters, Год журнала: 2025, Номер 52(3)

Опубликована: Фев. 9, 2025

Abstract Understanding internal variability of the climate system is critical when isolating and anthropogenically forced signals. Here, we investigate modes Atlantic Meridional Overturning Circulation ( AMOC ) using perturbation experiments with Institut Pierre‐Simon Laplace's (IPSL) coupled model compare them to Coupled Model Intercomparison Project Phase 6 (CMIP6) pre‐industrial control simulations. We identify two characteristic variability—decadal‐to‐multidecadal DMD var centennial CEN ). The former driven largely by temperature anomalies in subpolar North Atlantic, while latter salinity western Atlantic. amplitude each mode scales linearly mean strength IPSL experiments. correlates well across CMIP6 models, does not. These findings suggest that depends robustly on state, may be model‐dependent.

Язык: Английский

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Quantifying tipping behavior: Geometric early warnings and quasipotentials for a box model of AMOC

Chaos An Interdisciplinary Journal of Nonlinear Science, Год журнала: 2025, Номер 35(2)

Опубликована: Фев. 1, 2025

A non-autonomous system can undergo a rapid change of state in response to small or slow forcing, due the presence nonlinear processes that give rise critical transitions tipping points. Such are thought possible various subsystems (tipping elements) Earth’s climate system. The Atlantic Meridional Overturning Circulation (AMOC) is considered particular element where models varying complexity have shown potential for bi-stability and tipping. We consider both transient stochastic forcing simple but data-adapted model AMOC. propose test geometric early warning signal predict whether will occur large based on dynamics near an edge state. For we quantify mean times between noise-induced using Ordered Line Integral Method Cameron (2017) estimate quasipotential. calculate minimum action paths stable states scenarios. Finally, discuss problem finding warnings forcing.

Язык: Английский

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Noise-shaped hysteresis cycles of the AMOC under increasing CO2 forcing

Chaos An Interdisciplinary Journal of Nonlinear Science, Год журнала: 2025, Номер 35(2)

Опубликована: Фев. 1, 2025

The Atlantic Meridional Overturning Circulation (AMOC) stability landscape is commonly investigated with single-realization hysteresis diagrams driven by freshwater input in the North Ocean. However, effect of CO2 forcing on one side and role internal climate variability timing tipping AMOC other remain less explored. Here, we address this gap running three independent simulations, consisting a slow ramp-up plus ramp-down concentration (0.2 ppm/year) within PlaSim-Large-Scale Geostrophic (LSG) intermediate complexity model. We show that realizations CO2-driven cycle, particularly, recovery, are remarkably affected variability. In even observe reversed where recovers at higher level than collapse point. While statistical Early Warning Signals (EWSs) some success detecting points, also find EWS considerably reduces predictability leads to false positives an approaching tipping. suggest presence may have characteristics deviate substantially from behavior seen simple models caution needed when interpreting results single-experiment realization. Our findings highlight need for probabilistic approach defining “safe operating space” stability, since it might not be possible define single critical threshold prevent collapse.

Язык: Английский

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Limits to predictability of the asymptotic state of the Atlantic Meridional Overturning Circulation in a conceptual climate model

Physica D Nonlinear Phenomena, Год журнала: 2023, Номер 459, С. 134043 - 134043

Опубликована: Дек. 23, 2023

Anticipating critical transitions in the Earth system is of great societal relevance, yet there may be intrinsic limitations to their predictability. For instance, from theory dynamical systems possessing multiple chaotic attractors, it known that asymptotic state depends sensitively on initial condition proximity a fractal basin boundary. Here, we approach problem final-state sensitivity Atlantic Meridional Overturning Circulation (AMOC) using conceptual climate model, composed slow bistable ocean coupled fast atmosphere. First, explore occurrence long transients monostable regime, which can mask loss stability near bifurcations. In explicitly construct saddle edge tracking technique. Quantifying through maximum Lyapunov exponent and lifetime saddle, find exhibits boundary with almost full phase space dimension, implying vanishing predictability second kind Our results demonstrate usefulness studying non-attracting sets context predicting climatic tipping points, provide guidance for interpretation higher-dimensional models such as general circulation models.

Язык: Английский

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