Ocean's Role in Climate and Climate Change 

1. Atlantic Ocean Circualtion 

  • The ocean plays an important role in the climate system due to its very large heat capacity. It could delay the surface warming by absorbing much heat and redistributing it to the deep ocean, and by absorbing anthropogenic carbon dioxide. My focus is on the ocean circulation in the Atlantic, especailly the meridional overturning circulation (AMOC) or thermohaline circulation (THC). The AMOC transports more than 1 PW heat northward in the Atlantic and is critical for the climate over Europe and North America.

  • A cartoon of the global conveyor belt (from Kuhlbrodt). Red color shows surface warm currents and blue color shows cold currents at depth.



    2. Climate Impact of the AMOC 

  • The climate without an active AMOC would be much colder over the North Atlantic and surrounding regions. Some past abrupt climate changes such as the Younger Dryas and Heinrich events were caused by a siginificant weakening of the AMOC induced by the meltwater pulses from paleo-glaciers. In addition to surface air temperature, the AMOC also has a great impact on the tropical rainfall. Its change can cause north-south migration of the ITCZ, greatly impacting the Amazon rainforest and Sahel droughts.

  • Winter time surface air temperature change and annual precipitation change after a shutdown of the AMOC

    Related publications:

  • Yin, J., and R. J. Stouffer, 2007: Comparison of the stability of the Atlantic thermohaline circulation in two coupled atmosphere-ocean general circulation models. Journal of Climate, 20, 4293-4315.

  • Stouffer, R. J., J. Yin, J. M. Gregory, K. W. Dixon, M. J. Spelman, W. Hurlin, A. J. Weaver, M. Eby, G. M. Flato, H. Hasumi, A. Hu, J. H. Jungclaus, I. V. Kamenkovich, A. Levermann, M. Montoya, S. Murakami, S. Nawrath, A. Oka, W. R. Peltier, D. Y. Robitaille, A. Sokolov, G. Vettoretti, and S. L. Weber, 2006: Investigating the causes of the response of the thermohaline circulation to past and future climate changes. Journal of Climate, 19, 1365-1387.


  • 3. Sensitivity of the AMOC/THC to External Forcings 

  • The AMOC is sensitive to salinity and temperature anomalies (thermohaline forcing) at the high-latitude North Atlantic. Model projections suggest that the AMOC will weaken in response to global warming. The reason is that ocean surface warming and freshening at the high-latitude North Atlantic inhibits the sinking of the surface waters. Both the enhancement of global hydrological cycle and the melting of the Greenland Ice Sheet contribute to the surface freshening.

  • Sensitivity of the AMOC/THC to 0.1 Sv freshwater perturbation in the northern North Atlantic (14 AOGCMs + EMICs)

    Related publications:

  • Gregory, J. M., K. W. Dixon, R. J. Stouffer, A. J. Weaver, E. Driesschaert, M. Eby, T. Fichefet, H. Hasumi, A. Hu, Jungclaus, J. H., Kamenkovich, I. V., Levermann, A., Montoya, M., Murakami, S., Nawrath, S., Oka, A., Sokolov, A. P., Thorpe, R. B., 2005: A model intercomparison of changes in the Atlantic thermohaline circulation in response to increasing atmospheric CO2 concentration. Geophysical Research Letters, 32 (12), L12703, doi:10.1029/2005gl023209.


  • Stouffer, R. J., J. Yin, J. M. Gregory, K. W. Dixon, M. J. Spelman, W. Hurlin, A. J. Weaver, M. Eby, G. M. Flato, H. Hasumi, A. Hu, J. H. Jungclaus, I. V. Kamenkovich, A. Levermann, M. Montoya, S. Murakami, S. Nawrath, A. Oka, W. R. Peltier, D. Y. Robitaille, A. Sokolov, G. Vettoretti, and S. L. Weber, 2006: Investigating the causes of the response of the thermohaline circulation to past and future climate changes. Journal of Climate, 19, 1365-1387.