Mechanisms and Impacts of Earth System Tipping Elements

Reviews of Geophysics, Год журнала: 2023, Номер 61(1)

Опубликована: Фев. 16, 2023

Abstract Tipping elements are components of the Earth system which may respond nonlinearly to anthropogenic climate change by transitioning toward substantially different long‐term states upon passing key thresholds or “tipping points.” In some cases, such changes could produce additional greenhouse gas emissions radiative forcing that compound global warming. Improved understanding tipping is important for predicting future risks and their impacts. Here we review mechanisms, predictions, impacts, knowledge gaps associated with 10 notable proposed be elements. We evaluate approaching critical whether shifts manifest rapidly over longer timescales. Some have a higher risk crossing points under middle‐of‐the‐road pathways will possibly affect major ecosystems, patterns, and/or carbon cycling within 21st century. However, literature assessing scenarios indicates strong potential reduce impacts many through mitigation. The studies synthesized in our suggest most do not possess abrupt years, exhibit behavior, rather responding more predictably directly magnitude forcing. Nevertheless, uncertainties remain elements, highlighting an acute need further research modeling better constrain risks.

Язык: Английский

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Decadal Trends in the Oceanic Storage of Anthropogenic Carbon From 1994 to 2014

AGU Advances, Год журнала: 2023, Номер 4(4)

Опубликована: Авг. 1, 2023

Abstract The oceanic uptake and resulting storage of the anthropogenic CO 2 (C ant ) that humans have emitted into atmosphere moderates climate change. Yet our knowledge about how this has progressed in time remained limited. Here, we determine decadal trends C by applying eMLR(C*) regression method to ocean interior observations collected repeatedly since 1990s. We find global grew from 1994 2004 29 ± 3 Pg dec −1 2014 27 (±1σ). change second decade is 15 11% lower than one would expect first assuming proportional increase with atmospheric . attribute reduction sensitivity a decrease buffer capacity changes circulation. In Atlantic Ocean, maximum rate shifted Northern Southern Hemisphere, plausibly caused weaker formation North Deep Waters an intensified ventilation mode intermediate waters Hemisphere. Our estimates accumulation differ cumulative net air‐sea flux several , suggesting substantial variable, but uncertain loss natural carbon ocean. findings indicate considerable vulnerability sink variability

Язык: Английский

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A North Atlantic Warming Hole Without Ocean Circulation

Geophysical Research Letters, Год журнала: 2022, Номер 49(19)

Опубликована: Сен. 24, 2022

Abstract The sea surface temperature (SST) in the subpolar North Atlantic decreased during past century, a remarkable feature known as “warming hole (WH).” It is commonly claimed that WH results from slowdown of meridional overturning circulation. However, using an ensemble Community Earth System Model coupled to slab ocean model simulation, we show atmosphere alone can account for ∼50% observed cooling trend and ∼90% relative change global ocean. We find this caused by increased local westerlies response external forcing enhance heat loss through turbulent fluxes. This partly compensated damping SST warming due rise greenhouse gases. further suggest wind‐driven processes real world, but nonetheless ultimate driver resides atmosphere.

Язык: Английский

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Likely accelerated weakening of Atlantic overturning circulation emerges in optimal salinity fingerprint

Nature Communications, Год журнала: 2023, Номер 14(1)

Опубликована: Март 4, 2023

The long-term response of the Atlantic meridional overturning circulation (AMOC) to anthropogenic forcing has been difficult detect from short direct measurements available due strong interdecadal variability. Here, we present observational and modeling evidence for a likely accelerated weakening AMOC since 1980s under combined greenhouse gases aerosols. This signal can be detected in fingerprint salinity pileup remotely South Atlantic, but not classic warming hole locally North because latter is contaminated by "noise" Our optimal retains much trend forcing, while dynamically filtering out shorter climate Given ongoing our study indicates potential further acceleration with associated impacts coming decades.

Язык: Английский

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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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Internal multi-centennial variability of the Atlantic Meridional Overturning Circulation simulated by EC-Earth3

Climate Dynamics, Год журнала: 2022, Номер 60(11-12), С. 3695 - 3712

Опубликована: Окт. 21, 2022

Abstract We report a multi-centennial oscillation of the Atlantic Meridional Overturning Circulation (AMOC) simulated by EC-Earth3 climate model under pre-industrial climate. This has an amplitude ~ 6 Sv and period 150 years significantly impacts atmosphere. find that it is self-sustained low-frequency internal variability, driven accumulation salinity anomalies in Arctic their release into North Atlantic, affecting water column stability deep convection. Sea ice plays major role creating anomaly Arctic, while anomalous oceanic circulation, which drives exchange liquid freshwater between open ocean, main responsible for its southward propagation. Interestingly, simulations with increased greenhouse concentrations, therefore warmer climate, do not exhibit these strong AMOC fluctuations. hypothesize quasi-equilibrium global air surface temperature 4.5° higher than period, low amount sea high latitudes no longer able to trigger mechanism.

Язык: Английский

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Exceptional freshening and cooling in the eastern subpolar North Atlantic caused by reduced Labrador Sea surface heat loss

Ocean science, Год журнала: 2022, Номер 18(5), С. 1507 - 1533

Опубликована: Окт. 21, 2022

Abstract. Observations of the eastern subpolar North Atlantic in 2010s show exceptional freshening and cooling upper ocean, peaking 2016 with lowest salinities recorded for 120 years. Published theories mechanisms driving include: reduced transport saltier, warmer surface waters northwards from subtropics associated meridional overturning; shifts pathways fresher, cooler water Labrador Sea driven by changing patterns wind stress; eastward expansion gyre. Using output a high-resolution hindcast model simulation, we propose that primary cause is heat loss Sea. Tracking virtual fluid particles backwards between 1990 2020 shows major to be an increased outflow relatively fresh cold Sea; minor contribution warmer, saltier northward subtropics. The cooling, but not freshening, produced these proportions subtropical origin mitigated along-track atmosphere Current. We analyse modelled boundary exchanges mass transformation since 2000, while inflows lighter remain steady, increasing due beginning early 2000s. further upstream reveals source volume transported out recirculation water, therefore longer residence times, 500–1000 m

Язык: Английский

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Southern hemisphere eastern boundary upwelling systems emerging as future marine heatwave hotspots under greenhouse warming

Nature Communications, Год журнала: 2023, Номер 14(1)

Опубликована: Янв. 3, 2023

Abstract Marine heatwaves (MHWs) exert devastating impacts on ecosystems and have been revealed to increase in their incidence, duration, intensity response greenhouse warming. The biologically productive eastern boundary upwelling systems (EBUSs) are generally regarded as thermal refugia for marine species due buffering effects of ocean However, using an ensemble state-of-the-art high-resolution global climate simulations under a high carbon emission scenario, here we show that the MHW stress, measured annual cumulative MHWs, is projected faster Southern Hemisphere EBUSs (Humboldt Benguela current systems) than adjacent oceans. This mainly because additional warming caused by weakened currents overwhelms effect upwelling. Our findings suggest will emerge local hotspots MHWs future, potentially causing severe threats ecosystems.

Язык: Английский

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Human-induced changes in the global meridional overturning circulation are emerging from the Southern Ocean

Communications Earth & Environment, Год журнала: 2023, Номер 4(1)

Опубликована: Март 13, 2023

Abstract In a warming climate, the Global Meridional Overturning Circulation (GMOC) is expected to change significantly with risk of disrupting global redistribution ocean properties that sustains marine ecosystems, carbon cycle, and others. Here we make novel attempt utilize diagnostic & sea-ice model estimate GMOC its interdecadal changes since mid-1950s are consistent historical hydrographic observations. We find significant in have already occurred, most notably upper lower overturning cells Southern Ocean. The former has expanded poleward into denser water strengthened by 3–4 Sv mid-1970s, while latter contracted weakened similar rate during same period. These driven increasing Hemisphere (SH) Ferrel cell associated increases westerlies surface buoyancy loss over sinking branch, Antarctic meltwater discharge, response ozone depletion SH stratosphere atmospheric CO 2 . A large-scale readjustment seems be underway South Atlantic Indo-Pacific Oceans mid-2000s Ocean changes.

Язык: Английский

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Impacts and State‐Dependence of AMOC Weakening in a Warming Climate

Geophysical Research Letters, Год журнала: 2024, Номер 51(10)

Опубликована: Май 13, 2024

Abstract All climate models project a weakening of the Atlantic Meridional Overturning Circulation (AMOC) strength in response to greenhouse gas forcing. However, impacts AMOC decline alone cannot be isolated from other drivers change using existing Coupled Model Intercomparison Project simulations. To address this issue, we conduct idealized experiments EC‐Earth3 model. We compare an abrupt 4×CO 2 simulation with same experiment, except artificially fix at preindustrial levels. With design, can formally attribute differences between these two decline. In addition, quantify state‐dependence by comparing aforementioned which reduce strength. Our findings demonstrate that are state‐dependent, thus understanding on future requires targeted model experiments.

Язык: Английский

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