Future climate change shaped by inter-model differences in Atlantic Meridional Overturning Circulation response

Bellomo, Katinka; Angeloni, Michela; Corti, Susanna; Hardenberg, Jost von

doi:10.1002/essoar.10504664.3

Cited by 7 publications

(12 citation statements)

References 56 publications

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“…While AMOC variability is an important driver of North Atlantic temperature and salinity, as suggested by models 3,87 and observations 150 , uncertainties about its relative contribution exist. Indeed, other processes can also be important, including local atmospheric forcing 151,152 and external forcing 2,153 . Furthermore, coupled models tend to underestimate the magnitude of decadal SST variability in the North Atlantic compared to observations 154 , so the dominant mechanisms of decadal SST variability might differ between models and observations.…”

Section: Impacts On Heat and Freshwater Amoc Variability Can Affect A...mentioning

confidence: 99%

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The evolution of the North Atlantic Meridional Overturning Circulation since 1980

Jackson

Biastoch

Buckley

et al. 2022

Nat Rev Earth Environ

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The Atlantic Meridional Overturning Circulation (AMOC) (Box 1) is a system of ocean currents in the Atlantic that move warmer, upper waters northwards and cooler, deeper waters southwards. Accordingly, the AMOC is a major source of northward heat transport, accounting for 20-30% of total atmospheric and oceanic heat transport into the mid-latitudes 1 . The AMOC, therefore, has a key role in governing the climate of the North Atlantic region and beyond, influencing European air temperatures and precipitation, the frequency of Atlantic hurricanes and winter storms, spatial patterns of sea level and tropical monsoons 2,3 , and the global carbon budget 4 .The strength of the AMOC is typically 17 Sverdrups (Sv; 1 Sv = 10 6 m 3 s −1 ) 5 . However, both observations and models indicate that the AMOC exhibits substantial variability on daily to multi-decadal timescales. Coupled climate models suggest decadal variability can arise naturally due to internal interactions within the climate system [6][7][8] . The AMOC is also expected to respond to external forcing, including anthropogenic aerosols, volcanic eruptions and solar changes 9,10 , as well as anthropogenic greenhouse gas emissions 11 . Indeed, observations, reanalyses, models and proxies [12][13][14][15][16] indicate substantial contemporary decadal-scale changes in AMOC strength. The RAPID array at 26.5° N (refs 5,17 ), for example, revealed a statistically significant weakening from 2004 (refs 18,19 ), probably representing decadal variability rather than ongoing long-term weakening [20][21][22] . There are indications that the AMOC might be recovering in strength 12 .Despite evidence of decadal variability, many questions remain. For example, high-quality continuous observations, like the RAPID array, are short and sparse, making it difficult to assess longer-term AMOC variability and determine whether decadal changes are representative of those across the wider Atlantic. Moreover, there is uncertainty about the relative roles of internal variability and forced variability, owing to diverse AMOC variability 8,23 and externally forced AMOC trends 10,24 in models. Indeed, the AMOC might have already weakened over the twentieth century 25,26 , potentially implying that it is more sensitive to external forcing than previously thought. Understanding how and why the AMOC has changed on decadal timescales is thus crucial not only to understand the AMOC's role

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Section: Impacts On Heat and Freshwater Amoc Variability Can Affect A...mentioning

confidence: 99%

“…in shaping the climate of the North Atlantic relative to other influences 27,28 , but also to constrain predictions of future changes and AMOC impacts 2,29 .…”

mentioning

confidence: 99%

The evolution of the North Atlantic Meridional Overturning Circulation since 1980

Jackson

Biastoch

Buckley

et al. 2022

Nat Rev Earth Environ

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“…Climate change impacts, especially expected changes in precipitation regimes, differ widely across the globe, with large uncertainties in model predictions (e.g., Bellomo et al, 2021). Boreal forests in the northern hemisphere all are expected to experience increasing amounts of precipitation, and the conclusions drawn from our Swedish study, are thus likely transferable to boreal forests in general.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, not only changes in the amount of precipitation, but also in the variation of precipitation, or changes in the deposition form, for example, rain rather than mist, can substantially impact bryophyte physiology (cf., Metcalfe & Ahlstrand, 2019). In contrast, temperate forests in Central Europe, Australia and Southern America will face declining rainfall (cf., Bellomo et al, 2021; Millar & Stephenson, 2015), suggesting that opposing changes in environmental filters may act on forest bryophyte communities in these regions. It is possible that bryophyte communities of these forests will shift towards stress‐tolerant rather than towards competitive perennials.…”

Section: Discussionmentioning

confidence: 99%

Projected shifts in deadwood bryophyte communities under national climate and forestry scenarios benefit large competitors and impair small species

Löbel

Schröder

Snäll

2021

Journal of Biogeography

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Aim Climate change and habitat loss are the main threats to forest biodiversity. Deadwood bryophyte communities are composed of species with different functional traits and are affected by these processes. Grouping species depending on their traits can help to anticipate community responses to global change, and to potential conservation actions. Location National scale of Sweden. Taxon Deadwood bryophyte species (15 liverworts and 8 mosses). Methods Generalized linear mixed‐effects models were applied to test for differences in projected relative changes in habitat suitability (matching species’ requirements) among species with contrasting traits under varying climate and forest scenarios during the years 2020–2100. Projections were based on ensembles of species distribution models (GLM, Poisson point‐process, MaxEnt), climate scenarios and national scenarios of forest management and conservation. Results Shoot length was the best predictor of projected future changes in habitat suitability. Habitat suitabilities for small, short‐lived species will decline in a warmer and wetter macroclimate, whereas those for large, perennial species will increase. We expect stronger habitat suitability decreases for obligate than for facultative deadwood species. Increasing the proportion of set‐aside forests from 16% to 32%, and reducing the harvest levels in production forests, mitigated negative habitat trends of several sensitive species. However, the potential benefits of increased conservation were even larger for species with traits favoured by climate change, suggesting that these actions will also enhance the spread of these species. Main conclusions Climate change is expected to lead to shifts in boreal bryophyte communities towards large, competitive species and to an overall decrease in diversity. High investment in conservation actions seems necessary to maintain diversity. This should include increasing the area of forest set aside beyond 16%, and reducing harvest levels in production forests. However, whilst these actions may prevent species extinctions, at least in the short term, changes in community structure seem inevitable.

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“…Nonetheless, additional observational indicators including a "salinity pile-up" in the South Atlantic 10 support AMOC weakening, including a possible transition from a strong to a weak mode 11 . Such AMOC weakening is a robust feature of GHG-forced climate model simulations, thereby suggesting a likely cause [12][13][14][15][16][17] . Several studies have also shown the importance of anthropogenic aerosols (AAs) to multi-decadal AMOC variations 14,[18][19][20][21][22][23][24] .…”

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confidence: 95%

Air quality improvements are projected to weaken the Atlantic meridional overturning circulation through radiative forcing effects

Hassan

Allen

Liu

et al. 2022

Commun Earth Environ

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Observations indicate the Atlantic Meridional Overturning Circulation-a fundamental component of the ocean’s global conveyor belt-is weakening. Although causes remain uncertain, such weakening is consistent with increasing greenhouse gases. Recent studies also suggest that anthropogenic emissions associated with air pollution can impact the Atlantic Meridional Overturning Circulation. Here, we use four state-of-the-art chemistry-climate models to quantify how efforts to improve future air quality, via near-term climate forcer mitigation, will impact the Atlantic Meridional Overturning Circulation. Future reductions in aerosols, ozone and precursor gases alone induces end-of-century weakening of the Atlantic Meridional Overturning Circulation by up to 10%. However, when methane reductions are also included, this weakening is offset. The responses are best explained by changes in the North Atlantic radiative forcing. Thus, efforts to improve air quality must also target methane and other greenhouse gases including carbon dioxide to avoid weakening of the world’s major ocean circulation system.

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Future climate change shaped by inter-model differences in Atlantic Meridional Overturning Circulation response

Cited by 7 publications

References 56 publications

The evolution of the North Atlantic Meridional Overturning Circulation since 1980

The evolution of the North Atlantic Meridional Overturning Circulation since 1980

Projected shifts in deadwood bryophyte communities under national climate and forestry scenarios benefit large competitors and impair small species

Air quality improvements are projected to weaken the Atlantic meridional overturning circulation through radiative forcing effects

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