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

2016 ◽  
Vol 49 (5-6) ◽  
pp. 1495-1511 ◽  
Author(s):  
Annika Reintges ◽  
Thomas Martin ◽  
Mojib Latif ◽  
Noel S. Keenlyside
Keyword(s):  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
First Century ◽  
Cmip5 Models ◽  
Overturning Circulation ◽  
Meridional Overturning ◽  
Twenty First Century

scholarly journals Noise-induced transitions of the Atlantic Meridional Overturning Circulation in CMIP5 models

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Daniele Castellana ◽  
Henk A. Dijkstra
Keyword(s):  
Transition Probabilities ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Multiple Equilibrium ◽  
Cmip5 Models ◽  
Freshwater Flux ◽  
Overturning Circulation ◽  
Southern Boundary ◽  
Meridional Overturning ◽  
The Impact

AbstractBy studying transition probabilities of the Atlantic Meridional Overturning Circulation (AMOC) in an ensemble of CMIP5 climate models, we revisit one of the stability indicators of the AMOC, i.e. the freshwater transport carried by the AMOC at the southern boundary of the Atlantic basin. A correction to this indicator, based on the transition probabilities, is suggested to measure whether an AMOC state is in a multiple equilibrium regime or not. As a consequence, the AMOC of all CMIP5 models considered is in a multiple equilibrium regime and hence, in principle, a collapsed AMOC state should exist in each of these models. The results further demonstrate the dependence of the Atlantic surface freshwater flux on the AMOC and the impact of extreme events in the AMOC on temperatures in the North Atlantic region.

scholarly journals Intrinsic Variability of the Atlantic Meridional Overturning Circulation at Interannual-to-Multidecadal Time Scales

2015 ◽  
Vol 45 (7) ◽  
pp. 1929-1946 ◽  
Author(s):  
Sandy Grégorio ◽  
Thierry Penduff ◽  
Guillaume Sérazin ◽  
Jean-Marc Molines ◽  
Bernard Barnier ◽  
...  
Keyword(s):  
Time Scales ◽  
Gulf Stream ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Global Ocean ◽  
Intrinsic Variability ◽  
Meridional Heat Transport ◽  
Overturning Circulation ◽  
Spectral Peaks ◽  
Meridional Overturning

AbstractThe low-frequency variability of the Atlantic meridional overturning circulation (AMOC) is investigated from 2, ¼°, and ° global ocean–sea ice simulations, with a specific focus on its internally generated (i.e., “intrinsic”) component. A 327-yr climatological ¼° simulation, driven by a repeated seasonal cycle (i.e., a forcing devoid of interannual time scales), is shown to spontaneously generate a significant fraction R of the interannual-to-decadal AMOC variance obtained in a 50-yr “fully forced” hindcast (with reanalyzed atmospheric forcing including interannual time scales). This intrinsic variance fraction R slightly depends on whether AMOCs are computed in geopotential or density coordinates, and on the period considered in the climatological simulation, but the following features are quite robust when mesoscale eddies are simulated (at both ¼° and ° resolutions); R barely exceeds 5%–10% in the subpolar gyre but reaches 30%–50% at 34°S, up to 20%–40% near 25°N, and 40%–60% near the Gulf Stream. About 25% of the meridional heat transport interannual variability is attributed to intrinsic processes at 34°S and near the Gulf Stream. Fourier and wavelet spectra, built from the 327-yr ¼° climatological simulation, further indicate that spectral peaks of intrinsic AMOC variability (i) are found at specific frequencies ranging from interannual to multidecadal, (ii) often extend over the whole meridional scale of gyres, (iii) stochastically change throughout these 327 yr, and (iv) sometimes match the spectral peaks found in the fully forced hindcast in the North Atlantic. Intrinsic AMOC variability is also detected at multidecadal time scales, with a marked meridional coherence between 35°S and 25°N (15–30 yr periods) and throughout the whole basin (50–90-yr periods).

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