Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Indian Ocean warming can strengthen the Atlantic meridional overturning circulation


The slowdown of the Atlantic meridional overturning circulation (AMOC)1,2,3 and the accelerated warming of the tropical Indian Ocean (TIO)4,5,6 are two robust features projected for anthropogenic greenhouse warming, affecting both regional and global climates7,8. Here we use coupled climate simulations to investigate a previously overlooked link between the two phenomena. We demonstrate that TIO warming reduces rainfall over the tropical Atlantic by strengthening the Walker circulation and increasing atmospheric vertical stability. The resultant ocean salinity increase intensifies the AMOC as salinity anomalies are advected to northern high latitudes. In addition, TIO warming enhances westerly winds over the subpolar North Atlantic, which helps to maintain the stronger AMOC. A TIO warming of 0.1 °C above the mean warming of tropical oceans intensifies the AMOC by ~1 Sv, leading to a stronger interhemispheric asymmetry and a northward shifted ITCZ. Thus, TIO warming could delay the AMOC weakening under greenhouse warming. Indeed, we find that the AMOC weakens more strongly or completely collapses if we suppress TIO warming under the doubled and quadrupled CO2 scenarios. Simulations replicating the observed tropical ocean warming further confirm this TIO–AMOC link, suggesting that the observed TIO warming might be already playing a role in sustaining the AMOC.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: TIO warming since the mid-twentieth century.
Fig. 2: The effect of changing TIO SST on the AMOC.
Fig. 3: Global climate response to TIO warming.
Fig. 4: TIO control of the AMOC.

Data availability

The NOAA ERSST v4 data set is available at The data that support the findings of this study are available from the corresponding author upon request.

Code availability

We used the NCAR Command Language (NCL)40 for all the analyses and figures in this study, which is available from


  1. 1.

    Gregory, J. M. et al. A model intercomparison of changes in the atlantic thermohaline circulation in response to increasing atmospheric CO2 concentration. Geophys. Res. Lett. 32, L12703 (2005).

    Article  Google Scholar 

  2. 2.

    Cheng, W., Chiang, J. C. & Zhang, D. Atlantic meridional overturning circulation (AMOC) in CMIP5 models: RCP and historical simulations. J. Clim. 26, 7187–7197 (2013).

    Article  Google Scholar 

  3. 3.

    Rahmstorf, S. et al. Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation. Nat. Clim. Change 5, 475–480 (2015).

    Article  Google Scholar 

  4. 4.

    Du, Y. & Xie, S. P. Role of atmospheric adjustments in the tropical Indian Ocean warming during the 20th century in climate models. Geophys. Res. Lett. 35,, L08712 (2008).

    Article  Google Scholar 

  5. 5.

    Roxy, M. K., Ritika, K., Terray, P. & Masson, S. The curious case of Indian Ocean warming. J. Clim. 27, 8501–8509 (2014).

    Article  Google Scholar 

  6. 6.

    Dong, L. & Zhou, T. The Indian Ocean sea surface temperature warming simulated by CMIP5 models during the twentieth century: Competing forcing roles of GHGs and anthropogenic aerosols. J. Clim. 27, 3348–3362 (2014).

    Article  Google Scholar 

  7. 7.

    Sutton, R. T. & Hodson, D. L. Atlantic Ocean forcing of North American and European summer climate. Science 309, 115–118 (2005).

    CAS  Article  Google Scholar 

  8. 8.

    Han, W. et al. Indian Ocean decadal variability: a review. Bull. Am. Meteorol. Soc. 95, 1679–1703 (2014).

    Article  Google Scholar 

  9. 9.

    Trenberth, K. E. et al. Progress during TOGA in understanding and modeling global teleconnections associated with tropical sea surface temperatures. J. Geophys. Res. Oceans 103, 14291–14324 (1998).

    Article  Google Scholar 

  10. 10.

    Chiang, J. C. & Sobel, A. H. Tropical tropospheric temperature variations caused by ENSO and their influence on the remote tropical climate. J. Clim. 15, 2616–2631 (2002).

    Article  Google Scholar 

  11. 11.

    Xie, S. P. et al. Indian Ocean capacitor effect on Indo–Western Pacific climate during the summer following El Niño. J. Clim. 22, 730–747 (2009).

    Article  Google Scholar 

  12. 12.

    Di Lorenzo, E. et al. Central Pacific El Niño and decadal climate change in the North Pacific Ocean. Nat. Geosci. 3, 762–765 (2010).

    Article  Google Scholar 

  13. 13.

    Zhang, R. & Delworth, T. L. Impact of the Atlantic multidecadal oscillation on North Pacific climate variability. Geophys. Res. Lett. 34, L23708 (2007).

    Google Scholar 

  14. 14.

    Lee, S. K. et al. Pacific origin of the abrupt increase in Indian Ocean heat content during the warming hiatus. Nat. Geosci. 8, 445–449 (2015).

    CAS  Article  Google Scholar 

  15. 15.

    Abish, B., Cherchi, A. & Ratna, S. B. ENSO and the recent warming of the Indian Ocean. Int. J. Climatol. 38, 203–214 (2018).

    Article  Google Scholar 

  16. 16.

    Hoerling, M. P., Hurrell, J. W. & Xu, T. Tropical origins for recent North Atlantic climate change. Science 292, 90–92 (2001).

    CAS  Article  Google Scholar 

  17. 17.

    Cherchi, A. et al. The influence of tropical Indian Ocean SST on the Indian summer monsoon. J. Clim. 20, 3083–3105 (2007).

    Article  Google Scholar 

  18. 18.

    Cai, W. et al. Pantropical climate interactions. Science 363, eaav4236 (2019).

    Article  Google Scholar 

  19. 19.

    Xie, S. P. & Philander, S. G. H. A coupled ocean–atmosphere model of relevance to the ITCZ in the eastern Pacific. Tellus A Dyn. Meteorol. Oceanogr. 46, 340–350 (1994).

    Article  Google Scholar 

  20. 20.

    Stommel, H. Thermohaline convection with two stable regimes of flow. Tellus 13, 224–230 (1961).

    Article  Google Scholar 

  21. 21.

    Eden, C. & Jung, T. North Atlantic interdecadal variability: Oceanic response to the North Atlantic oscillation (1865–1997). J. Clim. 14, 676–691 (2001).

    Article  Google Scholar 

  22. 22.

    Delworth, T. L. et al. The North Atlantic oscillation as a driver of rapid climate change in the Northern Hemisphere. Nat. Geosci. 9, 509–512 (2016).

    CAS  Article  Google Scholar 

  23. 23.

    Frierson, D. M. et al. Contribution of ocean overturning circulation to tropical rainfall peak in the Northern Hemisphere. Nat. Geosci. 6, 940–944 (2013).

    CAS  Article  Google Scholar 

  24. 24.

    Kang, S. M., Held, I. M., Frierson, D. M. & Zhao, M. The response of the ITCZ to extratropical thermal forcing: Idealized slab-ocean experiments with a GCM. J. Clim. 21, 3521–3532 (2008).

    Article  Google Scholar 

  25. 25.

    Schneider, T., Bischoff, T. & Haug, G. H. Migrations and dynamics of the intertropical convergence zone. Nature 513, 45–53 (2014).

    CAS  Article  Google Scholar 

  26. 26.

    Bakker, P. et al. Fate of the Atlantic meridional overturning circulation: strong decline under continued warming and Greenland melting. Geophys. Res. Lett. 43, 12252–12260 (2016).

    Article  Google Scholar 

  27. 27.

    Sévellec, F., Fedorov, A. V. & Liu, W. Arctic sea-ice decline weakens the Atlantic meridional overturning circulation. Nat. Clim. Change 7, 604–610 (2017).

    Article  Google Scholar 

  28. 28.

    Liu, W., Xie, S. P., Liu, Z. & Zhu, J. Overlooked possibility of a collapsed Atlantic meridional overturning circulation in warming climate. Sci. Adv. 3, e1601666 (2017).

    Article  Google Scholar 

  29. 29.

    Durack, P. J. & Wijffels, S. E. Fifty-year trends in global ocean salinities and their relationship to broad-scale warming. J. Clim. 23, 4342–4362 (2010).

    Article  Google Scholar 

  30. 30.

    Smeed, D. A. et al. The North Atlantic Ocean is in a state of reduced overturning. Geophys. Res. Lett. 45, 1527–1533 (2018).

    Article  Google Scholar 

  31. 31.

    Caesar, L., Rahmstorf, S., Robinson, A., Feulner, G. & Saba, V. Observed fingerprint of a weakening Atlantic Ocean overturning circulation. Nature 556, 191 (2018).

    CAS  Article  Google Scholar 

  32. 32.

    Delworth, T. L. & Dixon, K. W. Have anthropogenic aerosols delayed a greenhouse gas‐induced weakening of the North Atlantic thermohaline circulation? Geophys. Res. Lett. 33, L02606 (2006).

    Article  Google Scholar 

  33. 33.

    Shi, J. R., Xie, S. P. & Talley, L. D. Evolving relative importance of the Southern Ocean and North Atlantic in anthropogenic ocean heat uptake. J. Clim. 31, 7459–7479 (2018).

    Article  Google Scholar 

  34. 34.

    Burls, N. J., Muir, L., Vincent, E. M. & Fedorov, A. Extra-tropical origin of equatorial Pacific cold bias in climate models with links to cloud albedo. Clim. Dyn. 49, 2093–2113 (2017).

    Article  Google Scholar 

  35. 35.

    Wang, C., Zhang, L., Lee, S. K., Wu, L. & Mechoso, C. R. A global perspective on CMIP5 climate model biases. Nat. Clim. Change 4, 201–205 (2014).

    Article  Google Scholar 

  36. 36.

    Hansen, J., Ruedy, R., Sato, M. & Lo, K. Global surface temperature change. Rev. Geophys. 48, RG4004 (2010).

    Article  Google Scholar 

  37. 37.

    Gent, P. R. et al. The community climate system model version 4. J. Clim. 24, 4973–4991 (2011).

    Article  Google Scholar 

  38. 38.

    Karspeck, A. R. et al. Comparison of the Atlantic meridional overturning circulation between 1960 and 2007 in six ocean reanalysis products. Clim. Dyn. 49, 957–982 (2017).

    Article  Google Scholar 

  39. 39.

    Xie, S. P. et al. Global warming pattern formation: sea surface temperature and rainfall. J. Clim. 23, 966–986 (2010).

    Article  Google Scholar 

  40. 40.

    NCAR Command Language v.6.6.2 (UCAR/NCAR/CISL/TDD, 2019);

Download references


A.V.F. was supported by grants from NSF (OCE-1756682, OPP-1741847), the ARCHANGE project of the “Make our planet great again” programme (CNRS, France) and the Guggenheim fellowship. S.H. was supported by the Scripps Institutional Postdoctoral Fellowship Program. We also acknowledge computational support from the NSF/NCAR Yellowstone/Cheyenne Supercomputing Center.

Author information




S.H. conceived the study, conducted the numerical simulations, performed the data analysis and led the writing of the manuscript. S.H. and A.V.F. together interpreted and explained the results and edited the manuscript.

Corresponding author

Correspondence to Shineng Hu.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information: Nature Climate Change thanks Claudia Frauen, Changhyun Yoo and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–17.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Hu, S., Fedorov, A.V. Indian Ocean warming can strengthen the Atlantic meridional overturning circulation. Nat. Clim. Chang. 9, 747–751 (2019).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing