scholarly journals The impact of resolution on the adjustment and decadal variability of the Atlantic meridional overturning circulation in a coupled climate model

2012 ◽  
Vol 39 (12) ◽  
pp. 3057-3073 ◽  
Author(s):  
Daniel L. R. Hodson ◽  
Rowan T. Sutton
Keyword(s):  
Climate Model ◽  
Decadal Variability ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Coupled Climate Model ◽  
Overturning Circulation ◽  
Meridional Overturning ◽  
The Impact

scholarly journals Climate impacts of a weakened Atlantic Meridional Overturning Circulation in a warming climate

2020 ◽  
Vol 6 (26) ◽  
pp. eaaz4876 ◽  
Author(s):  
Wei Liu ◽  
Alexey V. Fedorov ◽  
Shang-Ping Xie ◽  
Shineng Hu
Keyword(s):  
North Atlantic ◽  
Climate Model ◽  
Atlantic Meridional Overturning Circulation ◽  
Arctic Sea Ice ◽  
Climate Impacts ◽  
Meridional Overturning Circulation ◽  
Future Climate Change ◽  
Boreal Summer ◽  
Overturning Circulation ◽  
Meridional Overturning

While the Atlantic Meridional Overturning Circulation (AMOC) is projected to slow down under anthropogenic warming, the exact role of the AMOC in future climate change has not been fully quantified. Here, we present a method to stabilize the AMOC intensity in anthropogenic warming experiments by removing fresh water from the subpolar North Atlantic. This method enables us to isolate the AMOC climatic impacts in experiments with a full-physics climate model. Our results show that a weakened AMOC can explain ocean cooling south of Greenland that resembles the North Atlantic warming hole and a reduced Arctic sea ice loss in all seasons with a delay of about 6 years in the emergence of an ice-free Arctic in boreal summer. In the troposphere, a weakened AMOC causes an anomalous cooling band stretching from the lower levels in high latitudes to the upper levels in the tropics and displaces the Northern Hemisphere midlatitude jets poleward.

scholarly journals A New Index for the Atlantic Meridional Overturning Circulation at 26°N

2014 ◽  
Vol 27 (17) ◽  
pp. 6439-6455 ◽  
Author(s):  
A. Duchez ◽  
J. J.-M. Hirschi ◽  
S. A. Cunningham ◽  
A. T. Blaker ◽  
H. L. Bryden ◽  
...  
Keyword(s):  
Time Scales ◽  
Decadal Variability ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Ekman Transport ◽  
Current Estimate ◽  
Overturning Circulation ◽  
Main Hypothesis ◽  
Meridional Overturning ◽  
Sverdrup Transport

Abstract The Atlantic meridional overturning circulation (AMOC) has received considerable attention, motivated by its major role in the global climate system. Observations of AMOC strength at 26°N made by the Rapid Climate Change (RAPID) array provide the best current estimate of the state of the AMOC. The period 2004–11 when RAPID AMOC is available is too short to assess decadal variability of the AMOC. This modeling study introduces a new AMOC index (called AMOCSV) at 26°N that combines the Florida Straits transport, the Ekman transport, and the southward geostrophic Sverdrup transport. The main hypothesis in this study is that the upper midocean geostrophic transport calculated using the RAPID array is also wind-driven and can be approximated by the geostrophic Sverdrup transport at interannual and longer time scales. This index is expected to reflect variations in the AMOC at interannual to decadal time scales. This estimate of the surface branch of the AMOC can be constructed as long as reliable measurements are available for the Gulf Stream and for wind stress. To test the reliability of the AMOCSV on interannual and longer time scales, two different numerical simulations are used: a forced and a coupled simulation. Using these simulations the AMOCSV captures a substantial fraction of the AMOC variability and is in good agreement with the AMOC transport at 26°N on both interannual and decadal time scales. These results indicate that it might be possible to extend the observation-based AMOC at 26°N back to the 1980s.

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.

A New Pacific Influence on the Atlantic Meridional Overturning Circulation

2021 ◽  
Author(s):  
Leon Hermanson ◽  
Doug Smith ◽  
Nick Dunstone ◽  
Rosie Eade
Keyword(s):  
Decadal Variability ◽  
Atlantic Meridional Overturning Circulation ◽  
Tropical Pacific ◽  
Meridional Overturning Circulation ◽  
Western Boundary ◽  
Strong Impact ◽  
Overturning Circulation ◽  
Southern Us ◽  
Volcanic Forcing ◽  
Meridional Overturning

<p>The Atlantic Meridional Overturning Circulation (AMOC) at 26N has been measured since 2004 by the RAPID-MOCHA array. On a multi-year timescale it shows a decline with signs of a recovery since around 2012. This variability is likely to be part of longer decadal variability. We examine here the decadal variability of the AMOC and its drivers in a coupled model run nudged to observations from 1960-2017. Temperature and winds are nudged throughout the atmosphere and potential temperature and salinity are nudged in the ocean, but the ocean velocities are allowed to vary freely. We nudge an ensemble of 10 ocean analyses into the ocean model to get an ensemble of responses, the mean of which reproduces the observed AMOC. We use these ocean-atmosphere re-analyses to study the drivers of the AMOC. The North Atlantic Oscillation (NAO) is well known to have an impact on the AMOC and is an important driver here. We find that the tropical Pacific also has a strong impact on the subtropical AMOC on multi-annual to decadal timescales. Together these two factors can explain more than half of all variability of the AMOC at 26N through wind forcing associated with Rossby waves and western boundary waves. This Pacific impact, not reported on before, is from windstress curl anomalies close to the East Coast of the southern US due to changes in the Pacific storm track and the Walker Circulation. As both the NAO and tropical Pacific variability is associated with solar and volcanic forcing, it is possible that solar and volcanic forcing are important for multi-annual to multi-decadal AMOC variability. We use observations of the NAO and tropical Pacific to reconstruct the AMOC from 1870 to present day and predict a continued recovery in the future.</p>

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