• Ackermann, L., C. Danek, P. Gierz, and G. Lohmann, 2020: AMOC recovery in a multicentennial scenario using a coupled atmosphere–ocean–ice sheet model. Geophys. Res. Lett., 47, e2019GL086810, https://doi.org/10.1029/2019GL086810.

    • Crossref
    • Export Citation
  • Andrews, T., J. M. Gregory, and M. J. Webb, 2015: The dependence of radiative forcing and feedback on evolving patterns of surface temperature change in climate models. J. Climate, 28, 16301648, https://doi.org/10.1175/JCLI-D-14-00545.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bakker, P., and Coauthors, 2016: Fate of the Atlantic meridional overturning circulation: Strong decline under continued warming and Greenland melting. Geophys. Res. Lett., 43, 12 25212 260, https://doi.org/10.1002/2016GL070457.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Broecker, W. S., 1997: Thermohaline circulation, the Achilles heel of our climate system: Will man-made CO2 upset the current balance? Science, 278, 15821588, https://doi.org/10.1126/science.278.5343.1582.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Broecker, W. S., 1998: Paleocean circulation during the last deglaciation: A bipolar seesaw? Paleoceanography, 13, 119121, https://doi.org/10.1029/97PA03707.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Broecker, W. S., 2003: Does the trigger for abrupt climate change reside in the ocean or in the atmosphere? Science, 300, 15191522, https://doi.org/10.1126/science.1083797.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Buckley, M. W., and J. Marshall, 2016: Observations, inferences, and mechanisms of the Atlantic meridional overturning circulation: A review. Rev. Geophys., 54, 563, https://doi.org/10.1002/2015RG000493.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Burke, A., A. L. Stewart, J. F. Adkins, R. Ferrari, M. F. Jansen, and A. F. Thompson, 2015: The glacial mid-depth radiocarbon bulge and its implications for the overturning circulation. Paleoceanography, 30, 10211039, https://doi.org/10.1002/2015PA002778.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Butler, E., K. Oliver, J.-M. Hirschi, and J. Mecking, 2016: Reconstructing global overturning from meridional density gradients. Climate Dyn., 46, 25932610, https://doi.org/10.1007/s00382-015-2719-6.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Cheng, W., J. C. Chiang, and D. Zhang, 2013: Atlantic meridional overturning circulation (AMOC) in CMIP5 models: RCP and historical simulations. J. Climate, 26, 71877197, https://doi.org/10.1175/JCLI-D-12-00496.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Curry, W. B., and D. W. Oppo, 2005: Glacial water mass geometry and the distribution of δ13C of ΣCO2 in the western Atlantic Ocean. Paleoceanography, 20, PA1017, https://doi.org/10.1029/2004PA001021.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • de Boer, A. M., A. Gnanadesikan, N. R. Edwards, and A. J. Watson, 2010: Meridional density gradients do not control the Atlantic overturning circulation. J. Phys. Oceanogr., 40, 368380, https://doi.org/10.1175/2009JPO4200.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Dixon, K. W., T. L. Delworth, M. J. Spelman, and R. J. Stouffer, 1999: The influence of transient surface fluxes on North Atlantic overturning in a coupled GCM climate change experiment. Geophys. Res. Lett., 26, 27492752, https://doi.org/10.1029/1999GL900571.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Dufresne, J.-L., and Coauthors, 2013: Climate change projections using the IPSL-CM5 Earth system model: From CMIP3 to CMIP5. Climate Dyn., 40, 21232165, https://doi.org/10.1007/s00382-012-1636-1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Durack, P. J., S. E. Wijffels, and R. J. Matear, 2012: Ocean salinities reveal strong global water cycle intensification during 1950 to 2000. Science, 336, 455458, https://doi.org/10.1126/science.1212222.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ferrari, R., M. F. Jansen, J. F. Adkins, A. Burke, A. L. Stewart, and A. F. Thompson, 2014: Antarctic sea ice control on ocean circulation in present and glacial climates. Proc. Natl. Acad. Sci. USA, 111, 87538758, https://doi.org/10.1073/pnas.1323922111.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Frierson, D. M., and Coauthors, 2013: Contribution of ocean overturning circulation to tropical rainfall peak in the Northern Hemisphere. Nat. Geosci., 6, 940944, https://doi.org/10.1038/ngeo1987.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Frölicher, T., M. Aschwanden, N. Gruber, S. Jaccard, J. Dunne, and D. Paynter, 2020: Contrasting upper and deep ocean oxygen response to protracted global warming. Global Biogeochem. Cycles, 34, e2020GB006601, https://doi.org/10.1029/2020GB006601.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ganachaud, A., and C. Wunsch, 2003: Large-scale ocean heat and freshwater transports during the World Ocean Circulation Experiment. J. Climate, 16, 696705, https://doi.org/10.1175/1520-0442(2003)016<0696:LSOHAF>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Garuba, O. A., and P. J. Rasch, 2020: A partial coupling method to isolate the roles of the atmosphere and ocean in coupled climate simulations. J. Adv. Model. Earth Syst., 12, e2019MS002016, https://doi.org/10.1029/2019MS002016.

    • Crossref
    • Export Citation
  • Gebbie, G., 2014: How much did glacial North Atlantic water shoal? Paleoceanography, 29, 190209, https://doi.org/10.1002/2013PA002557.

  • Gent, P. R., 2018: A commentary on the Atlantic meridional overturning circulation stability in climate models. Ocean Modell., 122, 5766, https://doi.org/10.1016/j.ocemod.2017.12.006.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gnanadesikan, A., 1999: A simple predictive model for the structure of the oceanic pycnocline. Science, 283, 20772079, https://doi.org/10.1126/science.283.5410.2077.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gordon, A. L., 1986: Interocean exchange of thermocline water. J. Geophys. Res., 91, 50375046, https://doi.org/10.1029/JC091iC04p05037.

  • Gregory, J., and Coauthors, 2005: A model intercomparison of changes in the Atlantic thermohaline circulation in response to increasing atmospheric CO2 concentration. Geophys. Res. Lett., 32, L12703, https://doi.org/10.1029/2005GL023209.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Groeskamp, S., S. M. Griffies, D. Iudicone, R. Marsh, A. G. Nurser, and J. D. Zika, 2019: The water mass transformation framework for ocean physics and biogeochemistry. Annu. Rev. Mar. Sci., 11, 271305, https://doi.org/10.1146/annurev-marine-010318-095421.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Haskins, R. K., K. I. Oliver, L. C. Jackson, S. S. Drijfhout, and R. A. Wood, 2019: Explaining asymmetry between weakening and recovery of the AMOC in a coupled climate model. Climate Dyn., 53, 6779, https://doi.org/10.1007/s00382-018-4570-z.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Haskins, R. K., K. I. Oliver, L. C. Jackson, R. A. Wood, and S. S. Drijfhout, 2020: Temperature domination of AMOC weakening due to freshwater hosing in two GCMs. Climate Dyn., 54, 273286, https://doi.org/10.1007/s00382-019-04998-5.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • He, C., Z. Liu, and A. Hu, 2019: The transient response of atmospheric and oceanic heat transports to anthropogenic warming. Nat. Climate Change, 9, 222226, https://doi.org/10.1038/s41558-018-0387-3.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Held, I. M., and B. J. Soden, 2006: Robust responses of the hydrological cycle to global warming. J. Climate, 19, 56865699, https://doi.org/10.1175/JCLI3990.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Heuzé, C., K. J. Heywood, D. P. Stevens, and J. K. Ridley, 2015: Changes in global ocean bottom properties and volume transports in CMIP5 models under climate change scenarios. J. Climate, 28, 29172944, https://doi.org/10.1175/JCLI-D-14-00381.1.

    • Search Google Scholar
    • Export Citation
  • Hirschi, J. J.-M., and Coauthors, 2020: The Atlantic meridional overturning circulation in high-resolution models. J. Geophys. Res. Oceans, 125, e2019JC015522, https://doi.org/10.1029/2019JC015522.

    • Crossref
    • Export Citation
  • Holmes, R. M., J. D. Zika, R. Ferrari, A. F. Thompson, E. R. Newsom, and M. H. England, 2019: Atlantic Ocean heat transport enabled by Indo-Pacific heat uptake and mixing. Geophys. Res. Lett., 46, 13 93913 949, https://doi.org/10.1029/2019GL085160.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jackson, L. C., 2013: Shutdown and recovery of the AMOC in a coupled global climate model: The role of the advective feedback. Geophys. Res. Lett., 40, 11821188, https://doi.org/10.1002/grl.50289.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jackson, L. C., and Coauthors, 2020: Impact of ocean resolution and mean state on the rate of AMOC weakening. Climate Dyn., 55, 17111732, https://doi.org/10.1007/s00382-020-05345-9.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jansen, M. F., and L.-P. Nadeau, 2016: The effect of Southern Ocean surface buoyancy loss on the deep-ocean circulation and stratification. J. Phys. Oceanogr., 46, 34553470, https://doi.org/10.1175/JPO-D-16-0084.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jansen, M. F., and L.-P. Nadeau, 2019: A toy model for the response of the residual overturning circulation to surface warming. J. Phys. Oceanogr., 49, 12491268, https://doi.org/10.1175/JPO-D-18-0187.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Jansen, M. F., L.-P. Nadeau, and T. M. Merlis, 2018: Transient versus equilibrium response of the ocean’s overturning circulation to warming. J. Climate, 31, 51475163, https://doi.org/10.1175/JCLI-D-17-0797.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kostov, Y., K. C. Armour, and J. Marshall, 2014: Impact of the Atlantic meridional overturning circulation on ocean heat storage and transient climate change. Geophys. Res. Lett., 41, 21082116, https://doi.org/10.1002/2013GL058998.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Krebs, U., and A. Timmermann, 2007: Tropical air–sea interactions accelerate the recovery of the Atlantic meridional overturning circulation after a major shutdown. J. Climate, 20, 49404956, https://doi.org/10.1175/JCLI4296.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Levang, S. J., and R. W. Schmitt, 2020: What causes the AMOC to weaken in CMIP5? J. Climate, 33, 15351545, https://doi.org/10.1175/JCLI-D-19-0547.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lévy, M., P. Klein, A.-M. Tréguier, D. Iovino, G. Madec, S. Masson, and K. Takahashi, 2010: Modifications of gyre circulation by sub-mesoscale physics. Ocean Modell., 34 (1–2), 115, https://doi.org/10.1016/j.ocemod.2010.04.001.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Li, H., A. Fedorov, and W. Liu, 2021: AMOC stability and diverging response to Arctic sea ice decline in two climate models. J. Climate, 34, 54435460, https://doi.org/10.1175/JCLI-D-20-0572.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Liu, W., Z. Liu, and E. C. Brady, 2014: Why is the AMOC monostable in coupled general circulation models? J. Climate, 27, 24272443, https://doi.org/10.1175/JCLI-D-13-00264.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Liu, W., S.-P. Xie, Z. Liu, and J. Zhu, 2017: Overlooked possibility of a collapsed Atlantic meridional overturning circulation in warming climate. Sci. Adv., 3, e1601666, https://doi.org/10.1126/sciadv.1601666.

    • Crossref
    • Export Citation
  • Liu, W., A. V. Fedorov, S.-P. Xie, and S. Hu, 2020: Climate impacts of a weakened Atlantic meridional overturning circulation in a warming climate. Sci. Adv., 6, eaaz4876, https://doi.org/10.1126/sciadv.aaz4876.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lynch-Stieglitz, J., and Coauthors, 2007: Atlantic meridional overturning circulation during the Last Glacial Maximum. Science, 316, 6669, https://doi.org/10.1126/science.1137127.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Manabe, S., and R. J. Stouffer, 1994: Multiple-century response of a coupled ocean–atmosphere model to an increase of atmospheric carbon dioxide. J. Climate, 7, 523, https://doi.org/10.1175/1520-0442(1994)007<0005:MCROAC>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Maroon, E. A., J. E. Kay, and K. B. Karnauskas, 2018: Influence of the Atlantic meridional overturning circulation on the Northern Hemisphere surface temperature response to radiative forcing. J. Climate, 31, 92079224, https://doi.org/10.1175/JCLI-D-17-0900.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Marshall, J., A. Donohoe, D. Ferreira, and D. McGee, 2014: The ocean’s role in setting the mean position of the Inter-Tropical Convergence Zone. Climate Dyn., 42, 19671979, https://doi.org/10.1007/s00382-013-1767-z.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Mauritsen, T., and Coauthors, 2019: Developments in the MPI-M Earth System Model version 1.2 (MPI-ESM1.2) and its response to increasing CO2. J. Adv. Model. Earth Syst., 11, 9981038, https://doi.org/10.1029/2018MS001400.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McDougall, T. J., and P. M. Barker, 2011: Getting started with TEOS-10 and the Gibbs Seawater (GSW) Oceanographic Toolbox, SCOR/IAPSO WG127, Vol. 37, 28 pp., https://www.teos-10.org/pubs/Getting_Started.pdf

    • Crossref
    • Export Citation
  • Mecking, J., S. S. Drijfhout, L. C. Jackson, and T. Graham, 2016: Stable AMOC off state in an eddy-permitting coupled climate model. Climate Dyn., 47, 24552470, https://doi.org/10.1007/s00382-016-2975-0.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Muglia, J., and A. Schmittner, 2015: Glacial Atlantic overturning increased by wind stress in climate models. Geophys. Res. Lett., 42, 98629868, https://doi.org/10.1002/2015GL064583.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nadeau, L.-P., and M. F. Jansen, 2020: Overturning circulation pathways in a two-basin ocean model. J. Phys. Oceanogr., 50, 21052122, https://doi.org/10.1175/JPO-D-20-0034.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Newsom, E. R., and A. F. Thompson, 2018: Reassessing the role of the Indo-Pacific in the ocean’s global overturning circulation. Geophys. Res. Lett., 45, 12 42212 431, https://doi.org/10.1029/2018GL080350.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Newsom, E. R., C. M. Bitz, F. O. Bryan, R. Abernathey, and P. R. Gent, 2016: Southern Ocean deep circulation and heat uptake in a high-resolution climate model. J. Climate, 29, 25972619, https://doi.org/10.1175/JCLI-D-15-0513.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Newsom, E. R., A. F. Thompson, J. F. Adkins, and E. D. Galbraith, 2021: A hemispheric asymmetry in poleward ocean heat transport across climates: Implications for overturning and polar warming. Earth Planet. Sci. Lett., 568, 117033, https://doi.org/10.1016/j.epsl.2021.117033.

    • Crossref
    • Export Citation
  • Nikurashin, M., and G. Vallis, 2012: A theory of the interhemispheric meridional overturning circulation and associated stratification. J. Phys. Oceanogr., 42, 16521667, https://doi.org/10.1175/JPO-D-11-0189.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Pithan, F., and T. Jung, 2021: Arctic amplification of precipitation changes—The energy hypothesis. Geophys. Res. Lett., 48, e2021GL094977, https://doi.org/10.1029/2021GL094977.

    • Crossref
    • Export Citation
  • Ragen, S., K. C. Armour, L. Thompson, A. Shao, and D. Darr, 2022: The role of Atlantic basin geometry in meridional overturning circulation. J. Phys. Oceanogr., 52, 475492, https://doi.org/10.1175/JPO-D-21-0036.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rind, D., G. A. Schmidt, J. Jonas, R. Miller, L. Nazarenko, M. Kelley, and J. Romanski, 2018: Multicentury instability of the Atlantic meridional circulation in rapid warming simulations with GISS ModelE2. J. Geophys. Res. Atmos., 123, 63316355, https://doi.org/10.1029/2017JD027149.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rugenstein, M. A., J. M. Gregory, N. Schaller, J. Sedlácek, and R. Knutti, 2016a: Multiannual ocean–atmosphere adjustments to radiative forcing. J. Climate, 29, 56435659, https://doi.org/10.1175/JCLI-D-16-0312.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rugenstein, M. A., J. Sedlácek, and R. Knutti, 2016b: Nonlinearities in patterns of long-term ocean warming. Geophys. Res. Lett., 43, 33803388, https://doi.org/10.1002/2016GL068041.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rugenstein, M. A., and Coauthors, 2019: LongRunMIP: Motivation and design for a large collection of millennial-length AOGCM simulations. Bull. Amer. Meteor. Soc., 100, 25512570, https://doi.org/10.1175/BAMS-D-19-0068.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rugenstein, M. A., and Coauthors, 2020: Equilibrium climate sensitivity estimated by equilibrating climate models. Geophys. Res. Lett., 47, e2019GL083898, https://doi.org/10.1029/2019GL083898.

    • Crossref
    • Export Citation
  • Saint-Martin, D., and Coauthors, 2019: Fast-forward to perturbed equilibrium climate. Geophys. Res. Lett., 46, 89698975, https://doi.org/10.1029/2019GL083031.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Schmidt, G. A., and Coauthors, 2014: Configuration and assessment of the GISS ModelE2 contributions to the CMIP5 archive. J. Adv. Model. Earth Syst., 6, 141184, https://doi.org/10.1002/2013MS000265.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Schmittner, A., M. Latif, and B. Schneider, 2005: Model projections of the North Atlantic thermohaline circulation for the 21st century assessed by observations. Geophys. Res. Lett., 32, L23710, https://doi.org/10.1029/2005GL024368.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sévellec, F., A. V. Fedorov, and W. Liu, 2017: Arctic sea-ice decline weakens the Atlantic meridional overturning circulation. Nat. Climate Change, 7, 604610, https://doi.org/10.1038/nclimate3353.

    • Search Google Scholar
    • Export Citation
  • Sigmond, M., J. C. Fyfe, O. A. Saenko, and N. C. Swart, 2020: Ongoing AMOC and related sea-level and temperature changes after achieving the Paris targets. Nat. Climate Change, 10, 672677, https://doi.org/10.1038/s41558-020-0786-0.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Speer, K., and E. Tziperman, 1992: Rates of water mass formation in the North Atlantic Ocean. J. Phys. Oceanogr., 22, 93104, https://doi.org/10.1175/1520-0485(1992)022<0093:ROWMFI>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Stocker, T. F., and A. Schmittner, 1997: Influence of CO2 emission rates on the stability of the thermohaline circulation. Nature, 388, 862865, https://doi.org/10.1038/42224.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Stommel, H., 1961: Thermohaline convection with two stable regimes of flow. Tellus, 13, 224230, https://doi.org/10.3402/tellusa.v13i2.9491.

  • Stouffer, R. J., and S. Manabe, 2003: Equilibrium response of thermohaline circulation to large changes in atmospheric CO2 concentration. Climate Dyn., 20, 759773, https://doi.org/10.1007/s00382-002-0302-4.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Stouffer, R. J., and Coauthors, 2006: Investigating the causes of the response of the thermohaline circulation to past and future climate changes. J. Climate, 19, 13651387, https://doi.org/10.1175/JCLI3689.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sun, S., I. Eisenman, and A. L. Stewart, 2018: Does Southern Ocean surface forcing shape the global ocean overturning circulation? Geophys. Res. Lett., 45, 24132423, https://doi.org/10.1002/2017GL076437.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sun, S., I. Eisenman, L. Zanna, and A. L. Stewart, 2020a: Surface constraints on the depth of the Atlantic meridional overturning circulation: Southern Ocean versus North Atlantic. J. Climate, 33, 31253149, https://doi.org/10.1175/JCLI-D-19-0546.1.

    • Search Google Scholar
    • Export Citation
  • Sun, S., A. F. Thompson, and I. Eisenman, 2020b: Transient overturning compensation between Atlantic and Indo-Pacific basins. J. Phys. Oceanogr., 50, 21512172, https://doi.org/10.1175/JPO-D-20-0060.1.

    • Search Google Scholar
    • Export Citation
  • Sun, S., A. F. Thompson, S.-P. Xie, and S.-M. Long, 2022: Indo-Pacific warming induced by a weakening of the Atlantic meridional overturning circulation. J. Climate, 35, 815832, https://doi.org/10.1175/JCLI-D-21-0346.1.

    • Search Google Scholar
    • Export Citation
  • Thomas, M. D., and A. V. Fedorov, 2019: Mechanisms and impacts of a partial AMOC recovery under enhanced freshwater forcing. Geophys. Res. Lett., 46, 33083316, https://doi.org/10.1029/2018GL080442.

    • Search Google Scholar
    • Export Citation
  • Thorpe, R., J. M. Gregory, T. Johns, R. Wood, and J. Mitchell, 2001: Mechanisms determining the Atlantic thermohaline circulation response to greenhouse gas forcing in a non-flux-adjusted coupled climate model. J. Climate, 14, 31023116, https://doi.org/10.1175/1520-0442(2001)014<3102:MDTATC>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Vellinga, M., R. A. Wood, and J. M. Gregory, 2002: Processes governing the recovery of a perturbed thermohaline circulation in HadCM3. J. Climate, 15, 764780, https://doi.org/10.1175/1520-0442(2002)015<0764:PGTROA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Walin, G., 1982: On the relation between sea-surface heat flow and thermal circulation in the ocean. Tellus, 34, 187195, https://doi.org/10.3402/tellusa.v34i2.10801.

    • Search Google Scholar
    • Export Citation
  • Weaver, A. J., M. Eby, M. Kienast, and O. A. Saenko, 2007: Response of the Atlantic meridional overturning circulation to increasing atmospheric CO2: Sensitivity to mean climate state. Geophys. Res. Lett., 34, L05708, https://doi.org/10.1029/2006GL028756.

    • Search Google Scholar
    • Export Citation
  • Weber, S., and Coauthors, 2007: The modern and glacial overturning circulation in the Atlantic Ocean in PMIP coupled model simulations. Climate Past, 3, 5164, https://doi.org/10.5194/cp-3-51-2007.

    • Search Google Scholar
    • Export Citation
  • Weijer, W., W. Cheng, O. A. Garuba, A. Hu, and B. T. Nadiga, 2020: CMIP6 models predict significant 21st century decline of the Atlantic meridional overturning circulation. Geophys. Res. Lett., 47, e2019GL086075, https://doi.org/10.1029/2019GL086075.

  • Welander, P., 1971: A discussion on ocean currents and their dynamics—The thermocline problem. Philos. Trans. Roy. Soc., A270, 415421, https://doi.org/10.1098/rsta.1971.0081.

    • Search Google Scholar
    • Export Citation
  • Wiebe, E., and A. Weaver, 1999: On the sensitivity of global warming experiments to the parametrisation of sub-grid scale ocean mixing. Climate Dyn., 15, 875893, https://doi.org/10.1007/s003820050319.

    • Search Google Scholar
    • Export Citation
  • Wolfe, C. L., and P. Cessi, 2010: What sets the strength of the middepth stratification and overturning circulation in eddying ocean models? J. Phys. Oceanogr., 40, 15201538, https://doi.org/10.1175/2010JPO4393.1.

    • Search Google Scholar
    • Export Citation
  • Wu, P., L. Jackson, A. Pardaens, and N. Schaller, 2011: Extended warming of the northern high latitudes due to an overshoot of the Atlantic meridional overturning circulation. Geophys. Res. Lett., 38, L24704, https://doi.org/10.1029/2011GL049998.

    • Search Google Scholar
    • Export Citation
  • Yin, J., and R. J. Stouffer, 2007: Comparison of the stability of the Atlantic thermohaline circulation in two coupled atmosphere–ocean general circulation models. J. Climate, 20, 42934315, https://doi.org/10.1175/JCLI4256.1.

    • Search Google Scholar
    • Export Citation
  • Zhu, C., and Z. Liu, 2020: Weakening Atlantic overturning circulation causes South Atlantic salinity pile-up. Nat. Climate Change, 10, 9981003, https://doi.org/10.1038/s41558-020-0897-7.

    • Search Google Scholar
    • Export Citation
  • Zhu, J., Z. Liu, X. Zhang, I. Eisenman, and W. Liu, 2014: Linear weakening of the AMOC in response to receding glacial ice sheets in CCSM3. Geophys. Res. Lett., 41, 62526258, https://doi.org/10.1002/2014GL060891.

    • Search Google Scholar
    • Export Citation
  • Zhu, J., Z. Liu, J. Zhang, and W. Liu, 2015: AMOC response to global warming: Dependence on the background climate and response timescale. Climate Dyn., 44, 34493468, https://doi.org/10.1007/s00382-014-2165-x.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 1137 691 22
Full Text Views 455 310 12
PDF Downloads 529 343 10

Transient and Equilibrium Responses of the Atlantic Overturning Circulation to Warming in Coupled Climate Models: The Role of Temperature and Salinity

David B. BonanaCalifornia Institute of Technology, Pasadena, California

Search for other papers by David B. Bonan in
Current site
Google Scholar
PubMed
Close
,
Andrew F. ThompsonaCalifornia Institute of Technology, Pasadena, California

Search for other papers by Andrew F. Thompson in
Current site
Google Scholar
PubMed
Close
,
Emily R. NewsombUniversity of Oxford, Oxford, United Kingdom

Search for other papers by Emily R. Newsom in
Current site
Google Scholar
PubMed
Close
,
Shantong SunaCalifornia Institute of Technology, Pasadena, California

Search for other papers by Shantong Sun in
Current site
Google Scholar
PubMed
Close
, and
Maria RugensteincColorado State University, Fort Collins, Colorado

Search for other papers by Maria Rugenstein in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

The long-term response of the Atlantic meridional overturning circulation (AMOC) to climate change remains poorly understood, in part due to the computational expense associated with running atmosphere–ocean general circulation models (GCMs) to equilibrium. Here, we use a collection of millennial-length GCM simulations to examine the transient and equilibrium responses of the AMOC to an abrupt quadrupling of atmospheric carbon dioxide. We find that GCMs consistently simulate an AMOC weakening during the first century but exhibit diverse behaviors over longer time scales, showing different recovery levels. To explain the AMOC behavior, we use a thermal-wind expression, which links the overturning circulation to the meridional density difference between deep-water formation regions and the Atlantic basin. Using this expression, we attribute the evolution of the AMOC on different time scales to changes in temperature and salinity in distinct regions. The initial AMOC shoaling and weakening occurs on centennial time scales and is attributed to a warming of the deep-water formation region. A partial recovery of the AMOC occurs over the next few centuries, and is linked to a simultaneous warming of the Atlantic basin and a positive high-latitude salinity anomaly. The latter reduces the subsurface stratification and reinvigorates deep-water formation. GCMs that exhibit a prolonged AMOC weakening tend to have smaller high-latitude salinity anomalies and increased Arctic sea ice loss. After multiple millennia, the AMOC in some GCMs is stronger than the initial state due to warming of the low-latitude Atlantic. These results highlight the importance of considering high-latitude freshwater changes when examining the past and future evolution of the AMOC evolution on long time scales.

Significance Statement

The long-term response of the ocean’s global overturning circulation to warming remains poorly understood largely because it is expensive to run state-of-the-art climate models. This study makes use of a unique collection of millennial-length climate simulations from different climate models to examine the response of the Atlantic overturning circulation to warming on long time scales. We find that climate models consistently simulate a weakening of the Atlantic overturning circulation during the first century after warming, but disagree on long-term changes, showing different recovery levels of the Atlantic overturning circulation. Using a simple expression, which emulates the evolution of the Atlantic overturning circulation in climate models, we show that climate models with little to no recovery tend to have a small North Atlantic salinity anomaly while climate models with a stronger recovery tend to have a large North Atlantic salinity anomaly. These results highlight the importance of monitoring high-latitude freshwater sources throughout the twenty-first century and considering the relative role of temperature and salinity changes when examining the future and past evolution of the Atlantic overturning circulation on long time scales.

© 2022 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: David B. Bonan, dbonan@caltech.edu

Abstract

The long-term response of the Atlantic meridional overturning circulation (AMOC) to climate change remains poorly understood, in part due to the computational expense associated with running atmosphere–ocean general circulation models (GCMs) to equilibrium. Here, we use a collection of millennial-length GCM simulations to examine the transient and equilibrium responses of the AMOC to an abrupt quadrupling of atmospheric carbon dioxide. We find that GCMs consistently simulate an AMOC weakening during the first century but exhibit diverse behaviors over longer time scales, showing different recovery levels. To explain the AMOC behavior, we use a thermal-wind expression, which links the overturning circulation to the meridional density difference between deep-water formation regions and the Atlantic basin. Using this expression, we attribute the evolution of the AMOC on different time scales to changes in temperature and salinity in distinct regions. The initial AMOC shoaling and weakening occurs on centennial time scales and is attributed to a warming of the deep-water formation region. A partial recovery of the AMOC occurs over the next few centuries, and is linked to a simultaneous warming of the Atlantic basin and a positive high-latitude salinity anomaly. The latter reduces the subsurface stratification and reinvigorates deep-water formation. GCMs that exhibit a prolonged AMOC weakening tend to have smaller high-latitude salinity anomalies and increased Arctic sea ice loss. After multiple millennia, the AMOC in some GCMs is stronger than the initial state due to warming of the low-latitude Atlantic. These results highlight the importance of considering high-latitude freshwater changes when examining the past and future evolution of the AMOC evolution on long time scales.

Significance Statement

The long-term response of the ocean’s global overturning circulation to warming remains poorly understood largely because it is expensive to run state-of-the-art climate models. This study makes use of a unique collection of millennial-length climate simulations from different climate models to examine the response of the Atlantic overturning circulation to warming on long time scales. We find that climate models consistently simulate a weakening of the Atlantic overturning circulation during the first century after warming, but disagree on long-term changes, showing different recovery levels of the Atlantic overturning circulation. Using a simple expression, which emulates the evolution of the Atlantic overturning circulation in climate models, we show that climate models with little to no recovery tend to have a small North Atlantic salinity anomaly while climate models with a stronger recovery tend to have a large North Atlantic salinity anomaly. These results highlight the importance of monitoring high-latitude freshwater sources throughout the twenty-first century and considering the relative role of temperature and salinity changes when examining the future and past evolution of the Atlantic overturning circulation on long time scales.

© 2022 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: David B. Bonan, dbonan@caltech.edu
Save