Uncertainty in twenty-first century projections of the Atlantic Meridional Overturning Circulation in CMIP3 and CMIP5 models

Reintges, Annika; Martin, Thomas; Latif, Mojib; Keenlyside, Noel

doi:10.1007/s00382-016-3180-x

Cited by 81 publications

(68 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In coupled climate models the AMOC slows down in response to anthropogenic global warming (e.g., Collins et al, 2013;Gregory et al, 2005;Schmittner et al, 2005), although there is a large uncertainty in the amount of decrease (Reintges et al, 2017). For a subset of the CMIP5 models Drijfhout et al (2012) show that the ensemble average AMOC weakened by 1.5 Sv/K in the scenarios with the greatest warming and 2 Sv/K with the least.…”

Section: Amoc Stability Under Anthropogenic Forcingmentioning

confidence: 99%

Stability of the Atlantic Meridional Overturning Circulation: A Review and Synthesis

et al. 2019

View full text Add to dashboard Cite

The notion that the Atlantic Meridional Overturning Circulation (AMOC) can have more than one stable equilibrium emerged in the 1980s as a powerful hypothesis to explain rapid climate variability during the Pleistocene. Ever since, the idea that a temporary perturbation of the AMOC—or a permanent change in its forcing—could trigger an irreversible collapse has remained a reason for concern. Here we review literature on the equilibrium stability of the AMOC and present a synthesis that puts our understanding of past and future AMOC behavior in a unifying framework. This framework is based on concepts from Dynamical Systems Theory, which has proven to be an important tool in interpreting a wide range of model behavior. We conclude that it cannot be ruled out that the AMOC in our current climate is in, or close to, a regime of multiple equilibria. But there is considerable uncertainty in the location of stability thresholds with respect to our current climate state, so we have no credible indications of where our present‐day AMOC is located with respect to thresholds. We conclude by identifying gaps in our knowledge and proposing possible ways forward to address these gaps.

show abstract

Section: Amoc Stability Under Anthropogenic Forcingmentioning

confidence: 99%

Stability of the Atlantic Meridional Overturning Circulation: A Review and Synthesis

et al. 2019

View full text Add to dashboard Cite

show abstract

“…As the atmosphere warms faster than the surface ocean in RCP8.5, the weakening temperature contrast leads to reduced turbulent heat fluxes from the ocean to the atmosphere (similar to Brodeau and Koenigk [2016]; see details in section 3.2). The reduced ocean heat loss, enhanced freshwater input, and northward shift and weakening of the wind stress curl pattern lead to weaker overturning ( Figure S3) [Collins et al, 2013;Brodeau and Koenigk, 2016] and a weaker subpolar gyre circulation ( Figure S4) (similar to Yang and Saenko [2012] and Reintges et al [2016]). The result is a negative trend in ocean heat transport convergence in region B.…”

Section: Heat Budget Trends In the Norwegian Earth System Modelmentioning

confidence: 99%

Connecting ocean heat transport changes from the midlatitudes to the Arctic Ocean

Nummelin

Hezel

2017

Geophysical Research Letters

View full text Add to dashboard Cite

Under greenhouse warming, climate models simulate a weakening of the Atlantic Meridional Overturning Circulation and the associated ocean heat transport at midlatitudes but an increase in the ocean heat transport to the Arctic Ocean. These opposing trends lead to what could appear to be a discrepancy in the reported ocean contribution to Arctic amplification. This study clarifies how ocean heat transport affects Arctic climate under strong greenhouse warming using a set of the 21st century simulations performed within the Coupled Model Intercomparison Project. The results suggest that a future reduction in subpolar ocean heat loss enhances ocean heat transport to the Arctic Ocean, driving an increase in Arctic Ocean heat content and contributing to the intermodel spread in Arctic amplification. The results caution against extrapolating the forced oceanic signal from the midlatitudes to the Arctic.

show abstract

“…The inter-model spread in projected temperature is indeed strong over the North Atlantic Ocean (figure 3(e). The North Atlantic temperatures have been linked to the Atlantic Multidecadal Overturning Circulation (AMOC, Knight et al 2006 andZhang andDelworth 2006), which exhibits large uncertainties in climate projections, mainly because of a strong model-dependency (Reintges et al 2016). The spread in surface temperature change is also strong over the Sahel, due to the spread in precipitation over land.…”

Section: Future Changes In Sahel Precipitationmentioning

confidence: 99%

Impact of internal variability on projections of Sahel precipitation change

Monerie

Sánchez-Gómez

Pohl

et al. 2017

Environ. Res. Lett.

View full text Add to dashboard Cite

The impact of the increase of greenhouse gases on Sahelian precipitation is very uncertain in both its spatial pattern and magnitude. In particular, the relative importance of internal variability versus external forcings depends on the time horizon considered in the climate projection. In this study we address the respective roles of the internal climate variability versus external forcings on Sahelian precipitation by using the data from the CESM Large Ensemble Project, which consists of a 40 member ensemble performed with the CESM1-CAM5 coupled model for the period 1920-2100. We show that CESM1-CAM5 is able to simulate the mean and interannual variability of Sahel precipitation, and is representative of a CMIP5 ensemble of simulations (i.e. it simulates the same pattern of precipitation change along with equivalent magnitude and seasonal cycle changes as the CMIP5 ensemble mean). However, CESM1-CAM5 underestimates the long-term decadal variability in Sahel precipitation. For short-term (2010-2049) and mid-term (2030-2069) projections the simulated internal variability component is able to obscure the projected impact of the external forcing. For long-term (2060-2099) projections external forcing induced change becomes stronger than simulated internal variability. Precipitation changes are found to be more robust over the central Sahel than over the western Sahel, where climate change effects struggle to emerge. Ten (thirty) members are needed to separate the 10 year averaged forced response from climate internal variability response in the western Sahel for a long-term (short-term) horizon. Over the central Sahel two members (ten members) are needed for a long-term (short-term) horizon.

show abstract

Uncertainty in twenty-first century projections of the Atlantic Meridional Overturning Circulation in CMIP3 and CMIP5 models

Abstract: parameters may explain the uncertainty in the AMOC projection, deeper insight into the 36 mechanisms for AMOC is required to reach a more quantitative conclusion.

Cited by 81 publications

References 42 publications

Stability of the Atlantic Meridional Overturning Circulation: A Review and Synthesis

Stability of the Atlantic Meridional Overturning Circulation: A Review and Synthesis

Connecting ocean heat transport changes from the midlatitudes to the Arctic Ocean

Impact of internal variability on projections of Sahel precipitation change

Contact Info

Product

Resources

About