• Ba, J., and et al. , 2014: A multi-model comparison of Atlantic multidecadal variability. Climate Dyn., 43, 23332348, doi:10.1007/s00382-014-2056-1.

    • Search Google Scholar
    • Export Citation
  • Bjerknes, J., 1964: Atlantic air–sea interaction. Advances in Geophysics, Vol. 10, Academic Press, 1–82.

  • Booth, B. B. B., , N. J. Dunstone, , P. R. Halloran, , T. Andrews, , and N. Bellouin, 2012: Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability. Nature, 484, 228232, doi:10.1038/nature10946.

    • Search Google Scholar
    • Export Citation
  • Branstator, G., , and H. Teng, 2014: Is AMOC more predictable than North Atlantic heat content? J. Climate, 27, 35373550, doi:10.1175/JCLI-D-13-00274.1.

    • Search Google Scholar
    • Export Citation
  • Branstator, G., , H. Teng, , G. A. Meehl, , M. Kimoto, , J. R. Knight, , M. Latif, , and A. Rosati, 2012: Systematic estimates of initial-value decadal predictability for six AOGCMs. J. Climate, 25, 18271846, doi:10.1175/JCLI-D-11-00227.1.

    • Search Google Scholar
    • Export Citation
  • Bretherton, C. S., , M. Widmann, , V. P. Dymnikov, , J. M. Wallace, , and I. Bladé, 1999: The effective number of spatial degrees of freedom of a time-varying field. J. Climate, 12, 19902009, doi:10.1175/1520-0442(1999)012<1990:TENOSD>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Collins, M., , and B. Sinha, 2003: Predictability of decadal variations in the thermohaline circulation and climate. Geophys. Res. Lett., 30, 1306, doi:10.1029/2002GL016504.

    • Search Google Scholar
    • Export Citation
  • DelSole, T., , L. Jia, , and M. K. Tippett, 2013: Decadal prediction of observed and simulated sea surface temperatures. Geophys. Res. Lett., 40, 27732778, doi:10.1002/grl.50185.

    • Search Google Scholar
    • Export Citation
  • Delworth, T., , S. Manabe, , and R. J. Stouffer, 1993: Interdecadal variations of the thermohaline circulation in a coupled ocean–atmosphere model. J. Climate, 6, 19932011, doi:10.1175/1520-0442(1993)006<1993:IVOTTC>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Farneti, R., , and G. Vallis, 2011: Mechanisms of interdecadal climate variability and the role of ocean–atmosphere coupling. Climate Dyn., 36, 289308, doi:10.1007/s00382-009-0674-9.

    • Search Google Scholar
    • Export Citation
  • Gregory, J. M., and et al. , 2005: A model intercomparison of changes in the Atlantic thermohaline circulation in response to increasing atmospheric CO2 concentration. Geophys. Res. Lett.,32, L12703, doi:10.1029/2005GL023209.

  • Griffies, S. M., , and K. Bryan, 1997: Predictability of North Atlantic multidecadal climate variability. Science, 275, 181184, doi:10.1126/science.275.5297.181.

    • Search Google Scholar
    • Export Citation
  • Hurrell, J. W., , J. J. Hack, , D. Shea, , J. M. Caron, , and J. Rosinski, 2008: A new sea surface temperature and sea ice boundary dataset for the Community Atmosphere Model. J. Climate, 21, 51455153, doi:10.1175/2008JCLI2292.1.

    • Search Google Scholar
    • Export Citation
  • Kay, J. E., and et al. , 2015: The Community Earth System Model (CESM) Large Ensemble Project: A community resource for studying climate change in the presence of internal climate variability. Bull. Amer. Meteor. Soc., doi:10.1175/BAMS-D-13-00255.1, in press.

    • Search Google Scholar
    • Export Citation
  • Knight, J. R., 2009: The Atlantic multidecadal oscillation inferred from the forced climate response in coupled general circulation models. J. Climate, 22, 16101625, doi:10.1175/2008JCLI2628.1.

    • Search Google Scholar
    • Export Citation
  • Knight, J. R., , R. J. Allan, , C. K. Folland, , M. Vellinga, , and M. E. Mann, 2005: A signature of persistent natural thermohaline circulation cycles in observed climate. Geophys. Res. Lett.,32, L20708, doi:10.1029/2005GL024233.

  • Kravtsov, S., , and C. Spannagle, 2008: Multidecadal climate variability in observed and modeled surface temperatures. J. Climate, 21, 11041121, doi:10.1175/2007JCLI1874.1.

    • Search Google Scholar
    • Export Citation
  • Kushnir, Y., 1994: Interdecadal variations in North Atlantic sea surface temperature and associated atmospheric conditions. J. Climate, 7, 141157, doi:10.1175/1520-0442(1994)007<0141:IVINAS>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Lippold, J., , J. Grützner, , D. Winter, , Y. Lahaye, , A. Mangini, , and M. Christl, 2009: Does sedimentary 231Pa/230Th from the Bermuda rise monitor past Atlantic meridional overturning circulation? Geophys. Res. Lett.,36, L12601, doi:10.1029/2009GL038068.

  • Mann, M. E., , B. A. Steinman, , and S. K. Miller, 2014: On forced temperature changes, internal variability, and the AMO. Geophys. Res. Lett.,41, 3211–3219, doi:10.1002/2014GL059233.

  • Marini, C., , and C. Frankignoul, 2014: An attempt to deconstruct the Atlantic multidecadal oscillation. Climate Dyn., 43, 607625, doi:10.1007/s00382-013-1852-3.

    • Search Google Scholar
    • Export Citation
  • Medhaug, I., , and T. Furevik, 2011: North Atlantic 20th century multidecadal variability in coupled climate models: Sea surface temperature and ocean overturning circulation. Ocean Sci., 7, 389404, doi:10.5194/os-7-389-2011.

    • Search Google Scholar
    • Export Citation
  • Meehl, G. A., , C. Covey, , K. E. Taylor, , T. Delworth, , R. J. Stouffer, , M. Latif, , B. McAvaney, , and J. F. B. Mitchell, 2007: THE WCRP CMIP3 multimodel dataset: A new era in climate change research. Bull. Amer. Meteor. Soc., 88, 13831394, doi:10.1175/BAMS-88-9-1383.

    • Search Google Scholar
    • Export Citation
  • Meehl, G. A., and et al. , 2009: Decadal prediction: Can it be skillful? Bull. Amer. Meteor. Soc., 90, 14671485, doi:10.1175/2009BAMS2778.1.

    • Search Google Scholar
    • Export Citation
  • Meehl, G. A., and et al. , 2014: Decadal climate prediction: An update from the trenches. Bull. Amer. Meteor. Soc., 95, 243267, doi:10.1175/BAMS-D-12-00241.1.

    • Search Google Scholar
    • Export Citation
  • Mikolajewicz, U., , and R. Voss, 2000: The role of the individual air–sea flux components in CO2-induced changes of the ocean’s circulation and climate. Climate Dyn., 16, 627642, doi:10.1007/s003820000066.

    • Search Google Scholar
    • Export Citation
  • Msadek, R., , and C. Frankignoul, 2009: Atlantic multidecadal oceanic variability and its influence on the atmosphere in a climate model. Climate Dyn., 33, 4562, doi:10.1007/s00382-008-0452-0.

    • Search Google Scholar
    • Export Citation
  • Msadek, R., , K. W. Dixon, , T. L. Delworth, , and W. Hurlin, 2010: Assessing the predictability of the Atlantic meridional overturning circulation and associated fingerprints. Geophys. Res. Lett.,37, L19608, doi:10.1029/2010GL044517.

  • Munoz, E., , B. Kirtman, , and W. Weijer, 2011: Varied representation of the Atlantic meridional overturning across multidecadal ocean reanalyses. Deep-Sea Res., 58, 18481857.

    • Search Google Scholar
    • Export Citation
  • Otterå, O. H., , M. Bentsen, , H. Drange, , and L. Suo, 2010: External forcing as a metronome for Atlantic multidecadal variability. Nat. Geosci., 3, 688694, doi:10.1038/ngeo955.

    • Search Google Scholar
    • Export Citation
  • Pohlmann, H., , M. Botzet, , M. Latif, , A. Roesch, , M. Wild, , and P. Tschuck, 2004: Estimating the decadal predictability of a coupled AOGCM. J. Climate, 17, 44634472, doi:10.1175/3209.1.

    • Search Google Scholar
    • Export Citation
  • Rayner, D., and et al. , 2011: Monitoring the Atlantic meridional overturning circulation. Deep-Sea Res., 58, 17441753, doi:10.1016/j.dsr2.2010.10.056.

    • Search Google Scholar
    • Export Citation
  • Ritz, S. P., , T. F. Stocker, , J. O. Grimalt, , L. Menviel, , and A. Timmermann, 2013: Estimated strength of the Atlantic overturning circulation during the last deglaciation. Nat. Geosci., 6, 208212, doi:10.1038/ngeo1723.

    • Search Google Scholar
    • Export Citation
  • Schmith, T., , S. Yang, , E. Gleeson, , and T. Semmler, 2014: How much have variations in the meridional overturning circulation contributed to sea surface temperature trends since 1850? A study with the EC-Earth global climate model. J. Climate, 27, 63436357, doi:10.1175/JCLI-D-13-00651.1.

    • Search Google Scholar
    • Export Citation
  • Smith, T. M., , R. W. Reynolds, , T. C. Peterson, , and J. Lawrimore, 2008: Improvements to NOAA’s historical merged land–ocean surface temperature analysis (1880–2006). J. Climate, 21, 22832296, doi:10.1175/2007JCLI2100.1.

    • Search Google Scholar
    • Export Citation
  • Sutton, R. T., , and D. L. R. Hodson, 2005: Atlantic Ocean forcing of North American and European summer climate. Science, 309, 115118, doi:10.1126/science.1109496.

    • Search Google Scholar
    • Export Citation
  • Taylor, K. E., , R. J. Stouffer, , and G. A. Meehl, 2012: An overview of CMIP5 and the experiment design. Bull. Amer. Meteor. Soc., 93, 485498, doi:10.1175/BAMS-D-11-00094.1.

    • Search Google Scholar
    • Export Citation
  • Teng, H., , G. Branstator, , and G. A. Meehl, 2011: Predictability of the Atlantic overturning circulation and associated surface patterns in two CCSM3 climate change ensemble experiments. J. Climate, 24, 60546076, doi:10.1175/2011JCLI4207.1.

    • Search Google Scholar
    • Export Citation
  • Terray, L., 2012: Evidence for multiple drivers of North Atlantic multi-decadal climate variability. Geophys. Res. Lett.,39, L19712, doi:10.1029/2012GL053046.

  • Ting, M., , Y. Kushnir, , R. Seager, , and C. Li, 2009: Forced and internal twentieth-century SST trends in the North Atlantic. J. Climate, 22, 14691481, doi:10.1175/2008JCLI2561.1.

    • Search Google Scholar
    • Export Citation
  • Vellinga, M., , and P. Wu, 2004: Low-latitude freshwater influence on centennial variability of the Atlantic thermohaline circulation. J. Climate, 17, 44984511, doi:10.1175/3219.1.

    • 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, doi:10.1029/2006GL028756.

  • Wu, L., , and Z. Liu, 2005: North Atlantic decadal variability: Air–sea coupling, oceanic memory, and potential Northern Hemisphere resonance. J. Climate, 18, 331349, doi:10.1175/JCLI-3264.1.

    • Search Google Scholar
    • Export Citation
  • Yang, X., and et al. , 2013: A predictable AMO-like pattern in the GFDL fully coupled ensemble initialization and decadal forecasting system. J. Climate, 26, 650661, doi:10.1175/JCLI-D-12-00231.1.

    • Search Google Scholar
    • Export Citation
  • Zhang, L., , and C. Wang, 2013: Multidecadal North Atlantic sea surface temperature and Atlantic meridional overturning circulation variability in CMIP5 historical simulations. J. Geophys. Res. Oceans, 118, 57725791, doi:10.1002/jgrc.20390.

    • Search Google Scholar
    • Export Citation
  • Zhang, R., 2008: Coherent surface–subsurface fingerprint of the Atlantic meridional overturning circulation. Geophys. Res. Lett.,35, L20705, doi:10.1029/2008GL035463.

  • Zhang, R., and et al. , 2013: Have aerosols caused the observed Atlantic multidecadal variability? J. Atmos. Sci., 70, 11351144, doi:10.1175/JAS-D-12-0331.1.

    • Search Google Scholar
    • Export Citation
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Does External Forcing Interfere with the AMOC’s Influence on North Atlantic Sea Surface Temperature?

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  • 1 Department of Physics, University of Toronto, Toronto, Ontario, Canada
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Abstract

Numerous studies have suggested that variations in the strength of the Atlantic meridional overturning circulation (AMOC) may drive predictable variations in North Atlantic sea surface temperature (NASST). However, two recent studies have presented results suggesting that coupled models disagree on both the sign and the phasing of the correlation between AMOC and NASST indices. These studies analyzed linearly detrended output from twentieth-century historical simulations in phases 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5). The present study argues that the apparent disagreement among models arises from a comingling of two processes: 1) a bottom-up effect in which unforced AMOC changes lead to NASST changes of the same sign and 2) a top-down effect in which forced NASST changes lead to AMOC changes of the opposite sign. Linear detrending is not appropriate for separating these two effects because the time scales of forced and unforced variations are not well separated. After forced variations are properly removed, the models come into much closer agreement with each other. This argument is supported by analysis of CMIP5 historical simulations, as well as preindustrial control simulations and a 29-member ensemble of the Community Earth System Model, version 1, covering the period 1920–2005. Additional analysis is presented suggesting that, even after the data are linearly detrended, a significant portion of observed NASST persistence may be externally forced.

Corresponding author address: Dr. Neil F. Tandon, Department of Physics, University of Toronto, 60 St. George St., Toronto, ON M5S 1A7, Canada. E-mail: neil.tandon@utoronto.ca

Abstract

Numerous studies have suggested that variations in the strength of the Atlantic meridional overturning circulation (AMOC) may drive predictable variations in North Atlantic sea surface temperature (NASST). However, two recent studies have presented results suggesting that coupled models disagree on both the sign and the phasing of the correlation between AMOC and NASST indices. These studies analyzed linearly detrended output from twentieth-century historical simulations in phases 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5). The present study argues that the apparent disagreement among models arises from a comingling of two processes: 1) a bottom-up effect in which unforced AMOC changes lead to NASST changes of the same sign and 2) a top-down effect in which forced NASST changes lead to AMOC changes of the opposite sign. Linear detrending is not appropriate for separating these two effects because the time scales of forced and unforced variations are not well separated. After forced variations are properly removed, the models come into much closer agreement with each other. This argument is supported by analysis of CMIP5 historical simulations, as well as preindustrial control simulations and a 29-member ensemble of the Community Earth System Model, version 1, covering the period 1920–2005. Additional analysis is presented suggesting that, even after the data are linearly detrended, a significant portion of observed NASST persistence may be externally forced.

Corresponding author address: Dr. Neil F. Tandon, Department of Physics, University of Toronto, 60 St. George St., Toronto, ON M5S 1A7, Canada. E-mail: neil.tandon@utoronto.ca
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