Climate Dynamics

, Volume 42, Issue 11–12, pp 3323–3336 | Cite as

Response of the Atlantic meridional overturning circulation to a reversal of greenhouse gas increases

  • L. C. JacksonEmail author
  • N. Schaller
  • R. S. Smith
  • M. D. Palmer
  • M. Vellinga


The reversibility of the Atlantic meridional overturning circulation (AMOC) is investigated in multi-model experiments using global climate models (GCMs) where CO2 concentrations are increased by 1 or 2 % per annum to 2× or 4× preindustrial conditions. After a period of stabilisation the CO2 is decreased back to preindustrial conditions. In most experiments when the CO2 decreases, the AMOC recovers before becoming anomalously strong. This "overshoot" is up to an extra 18.2Sv or 104 % of its preindustrial strength, and the period with an anomalously strong AMOC can last for several hundred years. The magnitude of this overshoot is shown to be related to the build up of salinity in the subtropical Atlantic during the previous period of high CO2 levels. The magnitude of this build up is partly related to anthropogenic changes in the hydrological cycle. The mechanisms linking the subtropical salinity increase to the subsequent overshoot are analysed, supporting the relationship found. This understanding is used to explain differences seen in some models and scenarios. In one experiment there is no overshoot because there is little salinity build up, partly as a result of model differences in the hydrological cycle response to increased CO2 levels and partly because of a less aggressive scenario. Another experiment has a delayed overshoot, possibly as a result of a very weak AMOC in that GCM when CO2 is high. This study identifies aspects of overshoot behaviour that are robust across a multi-model and multi-scenario ensemble, and those that differ between experiments. These results could inform an assessment of the real-world AMOC response to decreasing CO2.


Climate AMOC GCM 



This work was supported by the Joint DECC/Defra Met Office Hadley Centre Climate Programme (GA01101). The FAMOUS experiments were integrated on HECToR, the UK National Supercomputing resource. Advice on the CCSM3.5 and CESM experiments from J. Sedláček is gratefully acknowledged. We acknowledge the World Climate Research Programme’s Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modeling groups (listed in Table 2 of this paper) for producing and making available their model output. For CMIP the U.S. Department of Energy’s Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals. We would also like to thank J. Kettleborough, I. Edmond and J. Gregory for developing tools and code for the downloading, archiving and analysis of CMIP5 data at the Met Office. Finally we wish to thank two anonymous reviewers for their comments which helped to improve this manuscript.


  1. Armour K, Eisenman I, Blanchard-Wrigglesworth E, McCusker K, Bitz C (2011) The reversibility of sea ice loss in a state-of-the-art climate model. Geophys Res Lett 38:L16705Google Scholar
  2. Barker S, Knorr G, Vautravers M, Diz P, Skinner L (2010) Extreme deepening of the Atlantic overturning circulation during deglaciation. Nat Geosci 3:567–571CrossRefGoogle Scholar
  3. Bentsen M, Bethke I, Debernard J, Iversen T, Kirkevåg A, Seland Ø, Drange H, Roelandt C, Seierstad I, Hoose C et al (2012) The Norwegian earth system model, NorESM1-M-Part 1: Description and basic evaluation. Geosci Model Dev Discuss 5:2843–2931CrossRefGoogle Scholar
  4. Bi D et al (2013) The ACCESS coupled model: description, control climate and evaluation. Aust Met Oceanog J (accepted)Google Scholar
  5. Boucher O, Halloran P, Burke E, Doutriaux-Boucher M, Jones C, Lowe J, Ringer M, Robertson E, Wu P (2012) Reversibility in an earth system model in response to CO2 concentration changes. Environ Res Lett 7(2):024,013CrossRefGoogle Scholar
  6. Brayshaw DJ, Woollings T, Vellinga M (2009) Tropical and extratropical responses of the North Atlantic atmospheric circulation to a sustained weakening of the MOC. J Clim 22:3146–3155CrossRefGoogle Scholar
  7. Collins W, Bitz C, Blackmon M, Bonan G, Bretherton C, Carton J, Chang P, Doney S, Hack J, Henderson T et al (2006) The community climate system model version 3 (CCSM3). J Clim 19(11):2122–2143CrossRefGoogle Scholar
  8. Collins W, Bellouin N, Doutriaux-Boucher M, Gedney N, Halloran P, Hinton T, Hughes J, Jones C, Joshi M, Liddicoat S et al (2011) Development and evaluation of an earth-system model—HadGEM2. Geosci Model Dev Discuss 4:997–1062CrossRefGoogle Scholar
  9. Danabasoglu G, Bates S, Briegleb B, Jayne S, Jochum M, Large W, Peacock S, Yeager S (2012) The CCSM4 ocean component. J Clim 25(5):1361–1389CrossRefGoogle Scholar
  10. De Boer AM, Gnanadesikan A, Edwards NR, Watson AJ (2010) Meridional density gradients do not control the Atlantic overturning circulation. J Phys Oceanogr 40:368–380. doi: 10.1175/2009JPO4200.1 CrossRefGoogle Scholar
  11. Delworth T, Broccoli A, Rosati A, Stouffer R, Balaji V, Beesley J, Cooke W, Dixon K, Dunne J, Dunne K et al (2006) GFDL’s CM2 global coupled climate models. Part I: formulation and simulation characteristics. J Clim 19(5):643–674CrossRefGoogle Scholar
  12. Dufresne J, Foujols M, Denvil S, Caubel A, Marti O, Aumont O, Balkanski Y, Bekki S, Bellenger H, Benshila R et al (2013) Climate change projections using the IPSL-CM5 earth system model: from CMIP3 to CMIP5. Clim Dyn 40:2123–2165Google Scholar
  13. Durack P, Wijffels S (2010) Fifty-year trends in global ocean salinities and their relationship to broad-scale warming. J Clim 23(16):4342–4362CrossRefGoogle Scholar
  14. Durack P, Wijffels S, Matear R (2012) Ocean salinities reveal strong global water cycle intensification during 1950 to 2000. Science 336(6080):455–458CrossRefGoogle Scholar
  15. Gent P, McWilliams J (1990) Isopycnal mixing in ocean circulation models. J Phys Oceanogr 20(1):150–155CrossRefGoogle Scholar
  16. Gent P, Yeager S, Neale R, Levis S, Bailey D (2010) Improvements in a half degree atmosphere/land version of the CCSM. Clim Dyn 34(6):819–833CrossRefGoogle Scholar
  17. Gent P, Danabasoglu G, Donner L, Holland M, Hunke E, Jayne S, Lawrence D, Neale R, Rasch P, Vertenstein M et al (2011) The community climate system model version 4. J Clim 24(19):4973–4991CrossRefGoogle Scholar
  18. Gordon C, Cooper C, Senior C, Banks H, Gregory J, Johns T, Mitchell J, Wood R (2000) The simulation of SST, sea ice extents and ocean heat transports in a version of the Hadley Centre coupled model without flux adjustments. Clim Dyn 16:147–16CrossRefGoogle Scholar
  19. Jungclaus JH, Fischer N, Haak H, Lohmann K, Marotzke J, Matei D, Mikolajewicz U, Notz D, von Storch JS (2013) Characteristics of the ocean simulations in MPIOM, the ocean component of the MPI-Earth system model. J Adv Model Earth Syst. doi: 10.1002/jame.20023
  20. Held I, Soden B (2006) Robust responses of the hydrological cycle to global warming. J Clim 19(21):5686–5699CrossRefGoogle Scholar
  21. Jacob D, Goettel H, Jungclaus J, Muskulus M, Podzun R, Marotzke J (2005) Slowdown of the thermohaline circulation causes enhanced maritime climate influence and snow cover over Europe. Geophys Res Lett 32. doi: 10.1029/2005GL023286
  22. Johns T, Gregory J, Ingram W, Johnson C, Jones A, Lowe J, Mitchell J, Roberts D, Sexton D, Stevenson D et al (2003) Anthropogenic climate change for 1860 to 2100 simulated with the hadcm3 model under updated emissions scenarios. Clim Dyn 20(6):583–612Google Scholar
  23. Lackner K (2003) A guide to CO2 sequestration. Science 300(5626):1677–1678CrossRefGoogle Scholar
  24. Levermann A, Griesel A, Hofmann M, Montoya M, Rahmstorf S (2005) Dynamic sea level changes following changes in the thermohaline circulation. Clim Dyn 24:347–354CrossRefGoogle Scholar
  25. Liu Z, Otto-Bliesner BL, He F, Brady EC, Tomas R, Clark PU, Carlson AE, Lynch-Stieglitz J, Curry W, Brook E, Erickson D, Jacob R, Kutzbach J, Cheng J (2009) Transient simulation of last deglaciation with a new mechanism for Bølling-Allerød warming. Science 325(5938):310–314. doi: 10.1126/science.1171041 CrossRefGoogle Scholar
  26. Martin G, Bellouin N, Collins WJ, Culverwell ID, Halloran PR, Hardiman SC, Hinton TJ, Jones CD, McDonald RE, McLaren AJ et al (2011) The HadGEM2 family of met office unified model climate configurations. Geosci Model Dev 4(3):723–757. doi: 10.5194/gmd-4-723-2011 CrossRefGoogle Scholar
  27. Mizuta R et al (2012) Climate simulations using MRI-AGCM3.2 with 20-km grid. J Meteorol Soc Jpn 90A:233–258CrossRefGoogle Scholar
  28. Nakashiki N, Kim D, Bryan F, Yoshida Y, Tsumune D, Maruyama K, Kitabata H (2006) Recovery of thermohaline circulation under CO2 stabilization and overshoot scenarios. Ocean Model 15(3):200–217CrossRefGoogle Scholar
  29. Pope V, Gallani M, Rowntree P, Stratton R (2000) The impact of new physical parameterizations in the Hadley Centre climate model: HadAM3. Clim Dyn 16:123–146CrossRefGoogle Scholar
  30. Roberts M, Marsh R, New A, Wood R (1996) An intercomparison of a Bryan-Cox type ocean model and an isopycnic ocean model. Part I: the subpolar gyre and high-latitude processes. J Phys Oceanogr 26(8):1495–1527CrossRefGoogle Scholar
  31. Roberts C, Garry F, Jackson L (2013) A multi-model study of sea surface temperature and sub-surface density fingerprints of the Atlantic meridional overturning circulation. J Clim (accepted)Google Scholar
  32. Rotstayn L, Jeffrey S, Collier M, Dravitzki S, Hirst A, Syktus J, Wong K (2012) Aerosol-induced changes in summer rainfall and circulation in the Australasian region: a study using single-forcing climate simulations. Atmos Chem Phys Discuss 12:5107–5188CrossRefGoogle Scholar
  33. Samanta A, Anderson B, Ganguly S, Knyazikhin Y, Nemani R, Myneni R (2010) Physical climate response to a reduction of anthropogenic climate forcing. Earth Interact 14(7):1–11CrossRefGoogle Scholar
  34. Smith R (2012) The FAMOUS climate model (versions XFXWB and XFHCC): description update to version XDBUA. Geosci Model Dev 5:269–276CrossRefGoogle Scholar
  35. Smith R, Gregory J (2009) A study of the sensitivity of ocean overturning circulation and climate to freshwater input in different regions of the North Atlantic. Geophys Res Lett 36(15):L15,701CrossRefGoogle Scholar
  36. Smith R, Gregory J, Osprey A (2008) A description of the FAMOUS (version XDBUA) climate model and control run. Geosci Model Dev 1:53–68. doi: 10.5194/gmd-1-53-2008 CrossRefGoogle Scholar
  37. Stouffer RJ, Yin J, Gregory JM, Dixon KW, Spelman MJ, Hurlin W, Weaver AJ, Eby M, Flato GM, Hasumi H, Hu A, Jungclaus JH, Kamenkovich V, Levermann A, Montoya M, Murakami S, Nawrath S, Oka A, Peltier WR, Robitaille DY, Sokolov A, Vettoretti G, Weber SL (2006) Investigating the causes of the response of the thermohaline circulation to past and future climate changes. J Clim 19: 1365–1387CrossRefGoogle Scholar
  38. Thorpe R, Gregory J, Johns T, Wood R, Mitchell J (2001) Mechanisms determining the Atlantic thermohaline circulation response to greenhouse gas forcing in a non-flux-adjusted coupled climate model. J Clim 14:3102–3116CrossRefGoogle Scholar
  39. Vellinga M (1998) Multiple equilibria in ocean models as a side effect of convective adjustment. J Phys Oceanogr 28(4):621–633CrossRefGoogle Scholar
  40. Vellinga M, Wood R (2002) Global climatic impacts of a collapse of the Atlantic thermohaline circulation. Clim Change 54:251–267CrossRefGoogle Scholar
  41. Vellinga M, Wood R (2008) Impacts of thermohaline circulation shutdown in the twenty-first century. Clim Change 91(1):43–63CrossRefGoogle Scholar
  42. Voldoire A, Sanchez-Gomez E, Salas y Mélia D, Decharme B, Cassou C, Sénési S, Valcke S, Beau I, Alias A, Chevallier M et al (2012) The CNRM-CM5.1 global climate model: description and basic evaluation. Clim Dyn. doi: 10.1007/s00382-011-1259-y
  43. von Salzen K et al (2013) The Canadian fourth generation atmospheric global climate model (CanAM4): simulation of clouds and precipitation and their responses to short-term climate variability. Atmos Ocean 51. doi: 10.1080/07055900.2012.755610
  44. Watanabe M, Suzuki T, O’ishi R, Komuro Y, Watanabe S, Emori S, Takemura T, Chikira M, Ogura T, Sekiguchi M et al (2010) Improved climate simulation by MIROC5: mean states, variability, and climate sensitivity. J Clim 23(23):6312–6335CrossRefGoogle Scholar
  45. Watanabe S, Hajima T, Sudo K, Nagashima T, Takemura T, Okajima H, Nozawa T, Kawase H, Abe M, Yokohata T, Ise T, Sato H, Kato E, Takata K, Emori S, Kawamiya M (2011) MIROC-ESM 2010: model description and basic results of CMIP5-20c3m experiments. Geosci Model Dev 4(4):845–872 doi: 10.5194/gmd-4-845-2011 CrossRefGoogle Scholar
  46. Weaver A, Sedláček J, Eby M, Alexander K, Crespin E, Fichefet T, Philippon-Berthier G, Joos F, Kawamiya M, Matsumoto K et al (2012) Stability of the atlantic meridional overturning circulation: a model intercomparison. Geophys Res Lett 39(20):L20,709CrossRefGoogle Scholar
  47. Wu P, Wood R, Ridley J, Lowe J (2010) Temporary acceleration of the hydrological cycle in response to a CO2 rampdown. Geophys Res Lett 37(12):L12,705Google Scholar
  48. Wu P, Jackson L, Pardaens A, Schaller N (2011) Extended warming of the northern high latitudes due to an overshoot of the Atlantic meridional overturning circulation. Geophys Res Lett 38(24):L24,704CrossRefGoogle Scholar

Copyright information

© Crown Copyright 2013

Authors and Affiliations

  • L. C. Jackson
    • 1
    Email author
  • N. Schaller
    • 2
  • R. S. Smith
    • 3
  • M. D. Palmer
    • 1
  • M. Vellinga
    • 1
  1. 1.Met Office Hadley CentreExeterUK
  2. 2.Institute for Atmospheric and Climate Science, ETH ZurichZurichSwitzerland
  3. 3.NCAS-Climate, Department of Meteorology, University of ReadingReadingUK

Personalised recommendations