scholarly journals Interacting tipping elements increase risk of climate domino effects under global warming

2020 ◽  
Author(s):  
Nico Wunderling ◽  
Jonathan F. Donges ◽  
Jürgen Kurths ◽  
Ricarda Winkelmann
Keyword(s):  
Global Warming ◽  
Southern Oscillation ◽  
Ice Sheets ◽  
Meridional Overturning Circulation ◽  
Climate System ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Temperature Thresholds ◽  
Earth’S Climate ◽  
The Individual

Abstract. There exists a range of subsystems in the climate system exhibiting threshold behaviour which could be triggered under global warming within this century resulting in severe consequences for biosphere and human societies. While their individual tipping thresholds are fairly well understood, it is of yet unclear how their interactions might impact the overall stability of the Earth's climate system. This cannot be studied yet with state-of-the-art Earth system models due to computational constraints as well as missing and uncertain process representations of some tipping elements. Here, we explicitly study the effects of known physical interactions between the Greenland and West Antarctic Ice Sheet, the Atlantic Meridional Overturning Circulation, the El-Nino Southern Oscillation and the Amazon rainforest using a conceptual network approach. We analyse the risk of domino effects being triggered by each of the individual tipping elements under global warming in equilibrium experiments, propagating uncertainties in critical temperature thresholds and interaction strengths via a Monte-Carlo approach. Overall, we find that the interactions tend to destabilise the network. Furthermore, our analysis reveals the qualitative role of each of the five tipping elements showing that the polar ice sheets on Greenland and West Antarctica are oftentimes the initiators of tipping cascades, while the AMOC acts as a mediator, transmitting cascades. This implies that the ice sheets, which are already at risk of transgressing their temperature thresholds within the Paris range of 1.5 to 2 °C, are of particular importance for the stability of the climate system as a whole.

scholarly journals Interacting tipping elements increase risk of climate domino effects under global warming

2021 ◽  
Vol 12 (2) ◽  
pp. 601-619
Author(s):  
Nico Wunderling ◽  
Jonathan F. Donges ◽  
Jürgen Kurths ◽  
Ricarda Winkelmann
Keyword(s):  
Global Warming ◽  
Global Climate ◽  
Ice Sheets ◽  
Meridional Overturning Circulation ◽  
Climate System ◽  
Critical Threshold ◽  
West Antarctic ◽  
Increased Risk ◽  
Temperature Thresholds ◽  
The Individual

Abstract. With progressing global warming, there is an increased risk that one or several tipping elements in the climate system might cross a critical threshold, resulting in severe consequences for the global climate, ecosystems and human societies. While the underlying processes are fairly well-understood, it is unclear how their interactions might impact the overall stability of the Earth's climate system. As of yet, this cannot be fully analysed with state-of-the-art Earth system models due to computational constraints as well as some missing and uncertain process representations of certain tipping elements. Here, we explicitly study the effects of known physical interactions among the Greenland and West Antarctic ice sheets, the Atlantic Meridional Overturning Circulation (AMOC) and the Amazon rainforest using a conceptual network approach. We analyse the risk of domino effects being triggered by each of the individual tipping elements under global warming in equilibrium experiments. In these experiments, we propagate the uncertainties in critical temperature thresholds, interaction strengths and interaction structure via large ensembles of simulations in a Monte Carlo approach. Overall, we find that the interactions tend to destabilise the network of tipping elements. Furthermore, our analysis reveals the qualitative role of each of the four tipping elements within the network, showing that the polar ice sheets on Greenland and West Antarctica are oftentimes the initiators of tipping cascades, while the AMOC acts as a mediator transmitting cascades. This indicates that the ice sheets, which are already at risk of transgressing their temperature thresholds within the Paris range of 1.5 to 2 ∘C, are of particular importance for the stability of the climate system as a whole.

Interactions of climate tipping elements and their associated basin stability in a conceptual model for tipping cascades

2021 ◽  
Author(s):  
Nico Wunderling ◽  
Jonathan Donges ◽  
Jürgen Kurths ◽  
Maximilian Gelbrecht ◽  
Ricarda Winkelmann
Keyword(s):  
Global Warming ◽  
Ice Sheet ◽  
Earth System ◽  
Internal Temperature ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
The Individual ◽  
Basin Stability

<p>With progressing global warming, there is an increased risk that one or several climate tipping elements might cross a critical threshold, resulting in severe consequences for the global climate, ecosystems and human societies. Here, we study a subset of four tipping elements and their interactions in a conceptual and easily extendable framework: the Greenland Ice Sheet, the West Antarctic Ice Sheet, the Atlantic Meridional Overturning Circulation (AMOC) and the Amazon rainforest.</p><p>In a large-scale Monte-Carlo simulation, we explicitly investigate the domino effects triggered by each of the individual tipping elements under global warming in equilibrium experiments. Thereby, we reveal the roles of each of the individual tipping elements in cascading transitions. Further, we perform a comprehensive basin stability analysis to detect the stable states of the interacting system and discuss their associated Earth system resilience. Finally, we analyse whether additional internal temperature feedbacks of the tipping elements might be able to increase the risk of triggering tipping events and cascades.</p><p>In our model experiments, we find: (i) the Greenland and the West Antarctic Ice Sheet are often the initiators of tipping cascades, while the AMOC typically takes on the role as a mediator of cascades. (ii) The interactions between the tipping elements considered here overall have a destabilizing effect on the climate system as a whole. (iii) In our model, the large ice sheets are of particular importance for the resilience of the Earth system on long time scales, as found by basin stability measures. (iv) Additional internal temperature feedbacks of the tipping elements can slightly increase the risk of triggering tipping events.</p>

Interacting tipping elements increase risk of climate domino effects

2020 ◽  
Author(s):  
Nico Wunderling ◽  
Jonathan Donges ◽  
Jürgen Kurths ◽  
Ricarda Winkelmann
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Meridional Overturning Circulation ◽  
Climate System ◽  
Amazon Rainforest ◽  
Freshwater Flux ◽  
West Antarctica ◽  
The Earth ◽  
Temperature Thresholds

<p>The Greenland Ice Sheet, West Antarctic Ice Sheet, Atlantic Meridional Overturning Circulation (AMOC), El-Nino Southern Oscillation (ENSO) and the Amazon rainforest have been identified as potential tipping elements in the Earth system, exhibiting threshold behavior. While their individual tipping thresholds are fairly well understood, it is of yet unclear how their interactions might impact the overall stability of the Earth’s climate system. Here, we explicitly study the effects of known physical interactions using a paradigmatic network approach which is not yet possible with more complex global circulation models or process-based models in a comprehensive way.</p><p>We analyze the risk of domino effects being triggered by each of the individual tipping elements under global warming in equilibrium experiments, propagating uncertainties in critical temperature thresholds and interaction strengths via a Monte-Carlo approach.</p><p>Overall, we find that the interactions tend to destabilize the network, with cascading failures occurring in 41% of cases in warming scenarios up to 2°C. More specifically, we uncover that:</p><p>(i) With increasing coupling strength, the temperature thresholds for inducing critical transitions are lowered significantly for West Antarctica, AMOC, ENSO and the Amazon rainforest. The dampening feedback loop between the Greenland Ice Sheet and the AMOC due to increased freshwater flux on the one hand and relative cooling around Greenland on the other, leads to an enhanced ambivalency whether the Greenland Ice Sheet tips or not.</p><p>(ii) Furthermore, our analysis reveals the role of each of the five tipping elements showing that the polar ice sheets on Greenland and West Antarctica are oftentimes the initiators of tipping cascades (in up to 40% of ensemble members for Greenland), while the AMOC acts as a mediator, transmitting cascades.</p><p>This implies that the ice sheets, which are already at risk of transgressing their temperature thresholds within the Paris range of 1.5 to 2°C, are of particular importance for the stability of the climate system as a whole.</p>

scholarly journals Dynamical processes involved in the retreat of marine ice sheets

2001 ◽  
Vol 47 (157) ◽  
pp. 271-282 ◽  
Author(s):  
Richard C.A. Hindmarsh ◽  
E. Le Meur
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Ice Streams ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Grounding Line ◽  
Neutral Equilibrium ◽  
Generally True

AbstractMarine ice sheets with mechanics described by the shallow-ice approximation by definition do not couple mechanically with the shelf. Such ice sheets are known to have neutral equilibria. We consider the implications of this for their dynamics and in particular for mechanisms which promote marine ice-sheet retreat. The removal of ice-shelf buttressing leading to enhanced flow in grounded ice is discounted as a significant influence on mechanical grounds. Sea-level rise leading to reduced effective pressures under ice streams is shown to be a feasible mechanism for producing postglacial West Antarctic ice-sheet retreat but is inconsistent with borehole evidence. Warming thins the ice sheet by reducing the average viscosity but does not lead to grounding-line retreat. Internal oscillations either specified or generated via a MacAyeal–Payne thermal mechanism promote migration. This is a noise-induced drift phenomenon stemming from the neutral equilibrium property of marine ice sheets. This migration occurs at quite slow rates, but these are sufficiently large to have possibly played a role in the dynamics of the West Antarctic ice sheet after the glacial maximum. Numerical experiments suggest that it is generally true that while significant changes in thickness can be caused by spatially uniform changes, spatial variability coupled with dynamical variability is needed to cause margin movement.

scholarly journals Suppression of marine ice sheet instability

2018 ◽  
Vol 857 ◽  
pp. 648-680 ◽  
Author(s):  
Samuel S. Pegler
Keyword(s):  
Steady State ◽  
Rapid Assessment ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Stable Steady State ◽  
Ice Shelf ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Grounding Line ◽  
The Stability

A long-standing open question in glaciology concerns the propensity for ice sheets that lie predominantly submerged in the ocean (marine ice sheets) to destabilise under buoyancy. This paper addresses the processes by which a buoyancy-driven mechanism for the retreat and ultimate collapse of such ice sheets – the marine ice sheet instability – is suppressed by lateral stresses acting on its floating component (the ice shelf). The key results are to demonstrate the transition between a mode of stable (easily reversible) retreat along a stable steady-state branch created by ice-shelf buttressing to tipped (almost irreversible) retreat across a critical parametric threshold. The conditions for triggering tipped retreat can be controlled by the calving position and other properties of the ice-shelf profile and can be largely independent of basal stress, in contrast to principles established from studies of unbuttressed grounding-line dynamics. The stability and recovery conditions introduced by lateral stresses are analysed by developing a method of constructing grounding-line stability (bifurcation) diagrams, which provide a rapid assessment of the steady-state positions, their natures and the conditions for secondary grounding, giving clear visualisations of global stabilisation conditions. A further result is to reveal the possibility of a third structural component of a marine ice sheet that lies intermediate to the fully grounded and floating components. The region forms an extended grounding area in which the ice sheet lies very close to flotation, and there is no clearly distinguished grounding line. The formation of this region generates an upsurge in buttressing that provides the most feasible mechanism for reversal of a tipped grounding line. The results of this paper provide conceptual insight into the phenomena controlling the stability of the West Antarctic Ice Sheet, the collapse of which has the potential to dominate future contributions to global sea-level rise.

scholarly journals Ice sheets viewed from the ocean: the contribution of marine science to understanding modern and past ice sheets

2012 ◽  
Vol 370 (1980) ◽  
pp. 5512-5539 ◽  
Author(s):  
Colm Ó Cofaigh
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Major Influence ◽  
Marine Science ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Technological Advances ◽  
Polar Ice Sheets ◽  
History Of ◽  
Geophysical Imaging

Over the last two decades, marine science, aided by technological advances in sediment coring, geophysical imaging and remotely operated submersibles, has played a major role in the investigation of contemporary and former ice sheets. Notable advances have been achieved with respect to reconstructing the extent and flow dynamics of the large polar ice sheets and their mid-latitude counterparts during the Quaternary from marine geophysical and geological records of landforms and sediments on glacier-influenced continental margins. Investigations of the deep-sea ice-rafted debris record have demonstrated that catastrophic collapse of large (10 5 –10 6  km 2 ) ice-sheet drainage basins occurred on millennial and shorter time scales and had a major influence on oceanography. In the last few years, increasing emphasis has been placed on understanding physical processes at the ice–ocean interface, particularly at the grounding line, and on determining how these processes affect ice-sheet stability. This remains a major challenge, however, owing to the logistical constraints imposed by working in ice-infested polar waters and ice-shelf cavities. Furthermore, despite advances in reconstructing the Quaternary history of mid- and high-latitude ice sheets, major unanswered questions remain regarding West Antarctic ice-sheet stability, and the long-term offshore history of the East Antarctic and Greenland ice sheets remains poorly constrained. While these are major research frontiers in glaciology, and ones in which marine science has a pivotal role to play, realizing such future advances will require an integrated collaborative approach between oceanographers, glaciologists, marine geologists and numerical modellers.

scholarly journals Marine ice-sheet profiles and stability under Coulomb basal conditions

2015 ◽  
Vol 61 (226) ◽  
pp. 205-215 ◽  
Author(s):  
Victor C. Tsai ◽  
Andrew L. Stewart ◽  
Andrew F. Thompson
Keyword(s):  
Power Law ◽  
Coulomb Friction ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Friction Behavior ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Grounding Line ◽  
Catastrophic Loss ◽  
Bed Slope

AbstractThe behavior of marine-terminating ice sheets, such as the West Antarctic ice sheet, is of interest due to the possibility of rapid grounding-line retreat and consequent catastrophic loss of ice. Critical to modeling this behavior is a choice of basal rheology, where the most popular approach is to relate the ice-sheet velocity to a power-law function of basal stress. Recent experiments, however, suggest that near-grounding line tills exhibit Coulomb friction behavior. Here we address how Coulomb conditions modify ice-sheet profiles and stability criteria. The basal rheology necessarily transitions to Coulomb friction near the grounding line, due to low effective stresses, leading to changes in ice-sheet properties within a narrow boundary layer. Ice-sheet profiles ‘taper off’ towards a flatter upper surface, compared with the power-law case, and basal stresses vanish at the grounding line, consistent with observations. In the Coulomb case, the grounding-line ice flux also depends more strongly on flotation ice thickness, which implies that ice sheets are more sensitive to climate perturbations. Furthermore, with Coulomb friction, the ice sheet grounds stably in shallower water than with a power-law rheology. This implies that smaller perturbations are required to push the grounding line into regions of negative bed slope, where it would become unstable. These results have important implications for ice-sheet stability in a warming climate.

scholarly journals Causes of Strengthening and Weakening of ENSO Amplitude under Global Warming in Four CMIP5 Models*

2015 ◽  
Vol 28 (8) ◽  
pp. 3250-3274 ◽  
Author(s):  
Lin Chen ◽  
Tim Li ◽  
Yongqiang Yu
Keyword(s):  
Global Warming ◽  
Wind Stress ◽  
Zonal Wind ◽  
Southern Oscillation ◽  
Heat Budget ◽  
Meridional Overturning Circulation ◽  
Cmip5 Models ◽  
Zonal Wind Stress ◽  
Equatorial Thermocline ◽  
Change In Mean

Abstract The mechanisms for El Niño–Southern Oscillation (ENSO) amplitude change under global warming are investigated through quantitative assessment of air–sea feedback processes in present-day and future climate simulations of four models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5). Two models (MPI-ESM-MR and MRI-CGCM3) project strengthened ENSO amplitude, whereas the other two models (CCSM4 and FGOALS-g2) project weakened ENSO amplitude. A mixed layer heat budget diagnosis shows that the major cause of the projected ENSO amplitude difference between the two groups is attributed to the changes of the thermocline and zonal advective feedbacks. A weaker (stronger) equatorial thermocline response to a unit anomalous zonal wind stress forcing in the Niño-4 region is found in CCSM4 and FGOALS-g2 (MPI-ESM-MR and MRI-CGCM3). The cause of the different response arises from the change in the meridional scale of ENSO. A narrower (wider) meridional width of sea surface temperature (SST) and zonal wind stress anomalies causes a strengthening (weakening) of the equatorial thermocline response and thus stronger Bjerknes and zonal advective feedbacks, as the subsurface temperature and zonal current anomalies depend on the thermocline response; consequently, the ENSO amplitude increases (decreases). The change of ENSO meridional width is caused by the change in mean meridional overturning circulation in the equatorial Pacific Ocean, which depends on change of mean wind stress and SST warming patterns under global warming.

scholarly journals The stability of grounding lines on retrograde slopes

2012 ◽  
Vol 6 (6) ◽  
pp. 1497-1505 ◽  
Author(s):  
G. H. Gudmundsson ◽  
J. Krug ◽  
G. Durand ◽  
L. Favier ◽  
O. Gagliardini
Keyword(s):  
Ice Sheets ◽  
Sea Level Change ◽  
The West ◽  
West Antarctic Ice Sheet ◽  
Level Change ◽  
West Antarctic ◽  
Per Se ◽  
Global Sea Level ◽  
The Stability ◽  
Near Future

Abstract. The stability of marine ice sheets grounded on beds that slope upwards in the overall direction of flow is investigated numerically in two horizontal dimensions. We give examples of stable grounding lines on such retrograde slopes illustrating that marine ice sheets are not unconditionally unstable in two horizontal dimensions. Retrograde bed slopes at the grounding lines of marine ice sheets, such as the West Antarctic Ice Sheet (WAIS), do not per se imply an instability, nor do they imply that these regions are close to a threshold of instability. We therefore question those estimates of the potential near-future contribution of WAIS to global sea level change based solely on the notion that WAIS, resting on a retrograde slope, must be inherently unstable.

scholarly journals Interhemispheric coupling, the West Antarctic Ice Sheet and warm Antarctic interglacials

2010 ◽  
Vol 6 (4) ◽  
pp. 431-443 ◽  
Author(s):  
P. B. Holden ◽  
N. R. Edwards ◽  
E. W. Wolff ◽  
N. J. Lang ◽  
J. S. Singarayer ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Sheet ◽  
Meridional Overturning Circulation ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Transient Simulations ◽  
Series Of Experiments ◽  
Atmospheric Co2 Concentrations ◽  
The Impact

Abstract. Ice core evidence indicates that even though atmospheric CO2 concentrations did not exceed ~300 ppm at any point during the last 800 000 years, East Antarctica was at least ~3–4 °C warmer than preindustrial (CO2~280 ppm) in each of the last four interglacials. During the previous three interglacials, this anomalous warming was short lived (~3000 years) and apparently occurred before the completion of Northern Hemisphere deglaciation. Hereafter, we refer to these periods as "Warmer than Present Transients" (WPTs). We present a series of experiments to investigate the impact of deglacial meltwater on the Atlantic Meridional Overturning Circulation (AMOC) and Antarctic temperature. It is well known that a slowed AMOC would increase southern sea surface temperature (SST) through the bipolar seesaw and observational data suggests that the AMOC remained weak throughout the terminations preceding WPTs, strengthening rapidly at a time which coincides closely with peak Antarctic temperature. We present two 800 kyr transient simulations using the Intermediate Complexity model GENIE-1 which demonstrate that meltwater forcing generates transient southern warming that is consistent with the timing of WPTs, but is not sufficient (in this single parameterisation) to reproduce the magnitude of observed warmth. In order to investigate model and boundary condition uncertainty, we present three ensembles of transient GENIE-1 simulations across Termination II (135 000 to 124 000 BP) and three snapshot HadCM3 simulations at 130 000 BP. Only with consideration of the possible feedback of West Antarctic Ice Sheet (WAIS) retreat does it become possible to simulate the magnitude of observed warming.

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