Current Atlantic Meridional Overturning Circulation weakest in last millennium

Caesar, Levke; McCarthy, Gerard; Thornalley, David; Cahill, Niamh; Rahmstorf, Stefan

doi:10.1038/s41561-021-00699-z

Cited by 292 publications

(241 citation statements)

References 13 publications

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“…Palaeoclimate records suggest that parts of Antarctica and larger parts of Greenland might already have experienced strong ice retreat in the past, especially during the Pliocene as well as during Marine Isotope Stage 5e and 11 (Dutton et al, 2015). It has also been shown that the AMOC experienced a significant slowdown since the mid 20th century (Caesar et al, 2018), which has led to the weakest AMOC state in centuries (Caesar et al, 2021). Models from Phase 5 of the Coupled Model Intercomparison Project (CMIP5) have shown Figure 1.…”

Section: Constraints From Current Observations and Palaeoclimatic Evidencementioning

confidence: 99%

“…A more frequent occurrence of El Niño events could have strong impacts on global ecosystems up to a potential dieback of the Amazon rainforest (Duque-Villegas et al, 2019). While some studies have emphasised the uncertainty about future ENSO changes (Kim et al, 2014;Collins et al, 2010), another study found that the frequency of El Niño events could increase twofold in climate change scenarios in sim-ulations of the CMIP3 and CMIP5 climate model ensembles as well as in perturbed physics experiments (Cai et al, 2014). Also, some ENSO characteristics appear to respond robustly to global warming (Kim et al, 2014;Power et al, 2013;Santoso et al, 2013), such as an intensification of ENSO-driven drying in the western Pacific and rainfall increases in the central and eastern equatorial Pacific due to non-linear responses to surface warming (Power et al, 2013).…”

Section: Structural Robustness and Sensitivity Analysis Including Ensomentioning

confidence: 99%

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

et al. 2021

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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.

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Section: Constraints From Current Observations and Palaeoclimatic Evidencementioning

confidence: 99%

Section: Structural Robustness and Sensitivity Analysis Including Ensomentioning

confidence: 99%

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

et al. 2021

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“…These impacts would be magnified and be reached relatively quickly (10-40 years), if a substantial amount of freshwater from Greenland's ice sheets is released into the North Atlantic. In light of recent observations of a substantial ice sheet loss and of the AMOC being currently at its weakest point in millennia 17,18 , our projections provide reasons of major concern for the future of species across major biodiversity hotspots. The effects of global warming and Greenland's melting would be reflected in substantial reductions to species diversity and alteration to species composition.…”

Section: Figures S4 S6)mentioning

confidence: 98%

Greenland’s thaw pushes the biodiversity crisis

Ureta

Ramírez‐Barahona

Calderón-Bustamante

et al. 2021

Preprint

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Anthropogenic greenhouse gas emissions have led to sustained global warming over the last decades1. This is already reshaping the distribution of biodiversity across the world and can lead to the occurrence of large-scale singular events, such as the melting of polar ice sheets2,3. The potential impacts of such a melting event on species persistence across taxonomic groups — in terms of magnitude and geographic extent — remain unexplored. Here we assess impacts on biodiversity of global warming and melting of Greenland's ice sheet on the distribution of 21,146 species of vascular plants and tetrapods across twelve megadiverse countries. We show that high global warming would lead to widespread reductions in species' geographic ranges (median range loss, 35–78%), which are magnified (median range loss, 95–99%) with the added contribution of Greenland's melting and its potentially large impact on oceanic circulation and regional climate changes. Our models project a decline in the geographical extent of species hotspots across countries (median reduction, 48–95%) and a substantial alteration of species composition in the near future (mean temporal dissimilarity, 0.26–0.89). These results imply that, in addition to global warming, the influence of Greenland's melting can lead to the collapse of biodiversity across the globe, providing an added domino in its cascading effects.

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“…shown that an AMOC regime shift in climate models might necessitate the knowledge of hundreds of years of time series of AMOC variations 50,52 , which is prohibitive with direct observations of it at 26°N that only last for less than 20 years 54 . Here, the reconstruction of our AMV as an internal mode of variability can be related to the internal dynamics of the AMOC through its impact on heat transport and the AMV 13,14,55 . Thus, the change in spectral characteristics of the AMV might be seen as a potential early warning of a regime shift [50][51][52] in the ocean circulation.…”

Section: Unforced Multidecadal Variability and Ongoing Bifurcationmentioning

confidence: 99%

A 1150-year-long AMV reconstruction suggests early warning for a North Atlantic climate tipping point

Michel¹,

Swingedouw²,

Mignot³

et al. 2021

Preprint

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The Atlantic Multidecadal Variability (AMV) is a large-scale climate phenomenon with crucial impacts on human societies and ecosystems. Its periodicity and drivers are controversial due to the short temporal extent of instrumental observations and competing impacts of external forcing and internal variability. Here, we use a well-verified set of paleoclimate proxy records and compare four regression methods to perform different reconstructions of the AMV since 850 C.E., built to only reflect internal variability in the Atlantic. The best performing reconstruction, when verified both against climate model outputs and independent proxy records is obtained using the non-linear random forest method. It exhibits large multi-decadal variations in the range of 20-90 years, a broader range than the 50-70 years identified in instrumental records. The reconstruction shows that AMV autocorrelation properties have experienced a significant change in the recent decades, suggesting an early warning signal for the proximity of a tipping point in the Atlantic.

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Current Atlantic Meridional Overturning Circulation weakest in last millennium

Cited by 292 publications

References 13 publications

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

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

Greenland’s thaw pushes the biodiversity crisis

A 1150-year-long AMV reconstruction suggests early warning for a North Atlantic climate tipping point

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