Climate of the Past Discussions www.clim-past-discuss.net 1814-9340 1814-9359 6 4 2010 10.5194/cpd-6-1267-2010 http://www.clim-past-discuss.net/6/1267/2010/ http://www.clim-past-discuss.net/6/1267/2010/cpd-6-1267-2010.html http://www.clim-past-discuss.net/6/1267/2010/cpd-6-1267-2010.pdf 1267 1309 2010-07-07 Variations of the Atlantic meridional overturning circulation in control and transient simulations of the last millennium D. Hofer dhofer@climate.unibe.ch C. C. Raible T. F. Stocker Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland The variability of the Atlantic meridional overturing circulation (AMOC) strength is investigated in control experiments and in transient simulations of up to the last millennium using the low-resolution Community Climate System Model version 3. In the transient simulations the AMOC exhibits enhanced low-frequency variability that is mainly caused by transitions between two semi-stable circulation states which amount to a 10 percent change of the maximum overturning. One transition is also found in a control experiment, but the time-varying external forcing significantly increases the probability of the occurrence of such events though not having a direct, linear impact on the AMOC. The transition from a high to a low AMOC state starts with a reduction of the convection in the Labrador and Irminger Seas and goes along with a changed barotropic circulation of both gyres in the North Atlantic and a gradual strengthening of the convection in the Greenland-Iceland-Norwegian (GIN) Seas. In contrast, the transition from a weak to a strong overturning is induced by decreased mixing in the GIN Seas. As a consequence of the transition, regional sea surface temperature (SST) anomalies are found in the midlatitude North Atlantic and in the convection regions with an amplitude of up to 3 K. The atmospheric response to the SST forcing associated with the transition indicates a significant impact on the Scandinavian surface air temperature (SAT) in the order of 1 K. Thus, the changes of the ocean circulation make a major contribution to the Scandinavian SAT variability in the last millennium. Ammann,~C M., Meehl,~G A., Washington,~W M., and Zender,~C S.: A~monthly and latitudinally varying volcanic forcing dataset in simulations of 20th century climate, Geophys. Res. Lett., 30, 1657, \doi10.1029/2003GL016875, 2003. Blunier,~T., Chappellaz,~J., Schwander,~J., Stauffer,~B., and Raynaud,~D.: Variations in atmospheric methane concentration during the Holocene epoch, Nature, 374, 46–49, \doi10.1038/374046a0, 1995. Briegleb,~B P., Bitz,~C M., Hunke,~E C., Lipscomb,~W H., Holland,~M M., Schramm,~J L., and Moritz,~R E.: Scientific description of the sea ice component in the Community Climate System Model, version 3, NCAR Tech. Note, NCAR/TN-463+STR, 70~pp., 2004. Briffa,~K R., Jones,~P D., Bartholin,~T S., Eckstein,~D., Schweingruber,~F H., Karlen,~W., Zetterberg,~P., and Eronen,~M.: Fennoscandian summers from AD-500 – temperature-changes on short and long timescales, Clim. Dynam., 7, 111–119, 1992. Broecker,~W S.: Was a~change in thermohaline circulation responsible for the Little Ice Age?, P. Natl. Acad. Sci. USA, 97, 1339–1342, 2000. Brohan,~P., Kennedy,~J J., Harris,~I., Tett,~S F B., and Jones,~P D.: Uncertainty estimates in regional and global observed temperature changes: A~new data set from 1850, J. Geophys. Res.-Atmos., 111, D12 106, \doi10.1029/2005JD006548, 2006. Bryan,~F O., Danabasoglu,~G., Nakashiki,~N., Yoshida,~Y., Kim,~D H., Tsutsui, ~J., and Doney,~S C.: Response of the North Atlantic thermohaline circulation and ventilation to increasing carbon dioxide in CCSM3, J. Climate, 19, 2382–2397, 2006. Büntgen,~U., Frank,~D C., Raible,~C C., Nievergelt,~D., Verstege,~A., Helama,~S., Hofer,~D., Wilson,~R J S., and Esper,~J.: Scandinavian temperatures contradict global warming, submitted, 2010. Clark,~P U., Pisias,~N G., Stocker,~T F., and Weaver,~A J.: The role of the thermohaline circulation in abrupt climate change, Nature, 415, 863–869, 2002. Collins,~W D., Bitz,~C M., Blackmon,~M L., Bonan,~G B., Bretherton,~C S., Carton,~J A., Chang,~P., Doney,~S C., Hack,~J J., Henderson,~T B., Kiehl,~J T., Large,~W G., McKenna,~D S., Santer,~B D., and Smith,~R D.: The Community Climate System Model version 3 (CCSM3), J. Climate, 19, 2122–2143, 2006a. Collins,~W D., Rasch,~P J., Boville,~B A., Hack,~J J., McCaa,~J R., Williamson,~D L., Briegleb,~B P., Bitz,~C M., Lin,~S J., and Zhang,~M H.: The formulation and atmospheric simulation of the Community Atmosphere Model version 3 (CAM3), J. Climate, 19, 2144–2161, 2006b. Crowley,~T J.: Causes of climate change over the past 1000~years, Science, 289, 270–277, 2000. Cubasch,~U., Voss,~R., Hegerl,~G C., Waszkewitz,~J., and Crowley,~T J.: Simulation of the influence of solar radiation variations on the global climate with an ocean-atmosphere general circulation model, Clim. Dynam., 13, 757–767, 1997. Cunningham,~S A., Kanzow,~T., Rayner,~D., Baringer,~M O., Johns,~W E., Marotzke,~J., Longworth,~H R., Grant,~E M., Hirschi,~J J M., Beal,~L M., Meinen,~C S., and Bryden,~H L.: Temporal variability of the Atlantic meridional overturning circulation at 26.5\degree N, Science, 317, 935–938, \doi10.1126/science.1141304, 2007. Dai,~A., Hu,~A., Meehl,~G A., Washington,~W M., and Strand,~W G.: Atlantic thermohaline circulation in a~coupled general circulation model: Unforced variations versus forced changes, J. Climate, 18, 3270–3293, 2005. Danabasoglu,~G.: On multidecadal variability of the Atlantic meridional overturning circulation in the Community Climate System Model version 3, J. Climate, 21, 5524–5544, \doi10.1175/2008JCLI2019.1, 2008. Delworth,~T., Manabe,~S., and Stouffer,~R J.: Interdecadal variations of the thermohaline circulation in a~coupled ocean-atmosphere model, J. Climate, 6, 1993–2011, 1993. Denton,~G H. and Broecker,~W S.: Wobbly ocean conveyor circulation during the Holocene?, Quaternary Sci. Rev., 27, 1939–1950, \doi10.1016/j.quascirev.2008.08.008, 2008. Dlugokencky,~E J., Houweling,~S., Bruhwiler,~L., Masarie,~K A., Lang,~P M., Miller,~J B., and Tans,~P P.: Atmospheric methane levels off: Temporary pause or a~new steady-state?, Geophys. Res. Lett., 30, 1992, \doi10.1029/2003GL018126, 2003. Dong,~B W. and Sutton,~R T.: Mechanism of interdecadal thermohaline circulation variability in a~coupled ocean-atmosphere GCM, J. Climate, 18, 1117–1135, 2005. D'Orgeville,~M. and Peltier,~W R.: Implications of both statistical equilibrium and global warming simulations with CCSM3. Part II: On the multidecadal variability in the North Atlantic basin, J. Climate, 22, 5298–5318, 2009. Enfield,~D B., Mestas-Nuñez,~A M., and Trimble,~P J.: The Atlantic multidecadal oscillation and its relation to rainfall and river flows in the continental US, Geophys. Res. Lett., 28, 2077–2080, 2001. Etheridge,~D M., Steele,~L P., Langenfelds,~R L., Francey,~R J., Barnola,~J M., and Morgan,~V I.: Natural and anthropogenic changes in atmospheric \chemCO_2 over the last 1000~years from air in Antarctic ice and firn, J. Geophys. Res.-Atmos., 101, 4115–4128, 1996. Flückiger,~J., Dallenbach,~A., Blunier,~T., Stauffer,~B., Stocker,~T F., Raynaud,~D., and Barnola,~J M.: Variations in atmospheric \chemN_2O concentration during abrupt climatic changes, Science, 285, 227–230, 1999. Flückiger,~J., Monnin,~E., Stauffer,~B., Schwander,~J., Stocker,~T F., Chappellaz,~J., Raynaud,~D., and Barnola,~J M.: High-resolution Holocene \chemN_2O ice core record and its relationship with \chemCH_4 and \chemCO_2, Global Biogeochem. Cy., 16, 1010, \doi10.1029/2001GB001417, 2002. Frank,~D C., Esper,~J., Raible,~C C., Büntgen,~U., Trouet,~V., Stocker,~B., and Joos,~F.: Ensemble reconstruction constraints on the global carbon cycle sensitivity to climate, Nature, 463, 527–U143, \doi10.1038/nature08769, 2010. Fröhlich,~C. and Lean,~J.: Solar radiative output and its variability: Evidence and mechanisms, Astron. Astrophys. Rev., 12, 273–320, 2004. Goosse,~H. and Renssen,~H.: Regional response of the climate system to solar forcing: The role of the ocean, Space Sci. Rev., 125, 227–235, \doi10.1007/s11214-006-9059-0, 2006. Gregory,~J M., Dixon,~K W., Stouffer,~R J., Weaver,~A J., Driesschaert,~E., Eby,~M., Fichefet,~T., Hasumi,~H., Hu,~A., Jungclaus,~J H., Kamenkovich,~I V., Levermann,~A., Montoya,~M., Murakami,~S., Nawrath,~S., Oka,~A., Sokolov,~A P., and Thorpe,~R B.: A~model intercomparison of changes in the Atlantic thermohaline circulation in response to increasing atmospheric CO₂ concentration, Geophys. Res. Lett., 32, L12 703, \doi10.1029/2005GL023209, 2005. Helama,~S., Timonen,~M., Holopainen,~J., Ogurtsov,~M G., Mielikainen,~K., Eronen,~M., Lindholm,~M., and Merilainen,~J.: Summer temperature variations in Lapland during the Medieval Warm Period and the Little Ice Age relative to natural instability of thermohaline circulation on multi-decadal and multi-centennial scales, J. Quaternary Sci., 24, 450–456, \doi10.1002/jqs.1291, 2009. Hurrell,~J W., Visbeck,~M., Busalacchi,~A., Clarke,~R A., Delworth,~T L., Dickson,~R R., Johns,~W E., Koltermann,~K P., Kushnir,~Y., Marshall,~D., Mauritzen,~C., McCartney,~M S., Piola,~A., Reason,~C., Reverdin,~G., Schott,~F., Sutton,~R., Wainer,~I., and Wright,~D.: Atlantic climate variability and predictability: A~CLIVAR perspective, J. Climate, 19, 5100–5121, 2006. IPCC: Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, UK and New York, NY, USA, 2001. IPCC: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Forth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, UK and New York, NY, USA, 2007. Jungclaus,~J H., Haak,~H., Latif,~M., and Mikolajewicz,~U.: Arctic-North Atlantic interactions and multidecadal variability of the meridional overturning circulation, J. Climate, 18, 4013–4031, 2005. Keeling,~C D. and Whorf,~T P.: Atmospheric \chemCO_2 records from sites in the SIO air sampling network, in: Trends: A~Compendium of Data on Global Change, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, US Department of Energy, Oak Ridge, TN, 2005. Kiehl,~J T., Shields,~C A., Hack,~J J., and Collins,~W D.: The climate sensitivity of the Community Climate System Model version 3 (CCSM3), J. Climate, 19, 2584–2596, 2006. Lean,~J., Beer,~J., and Bradley,~R.: Reconstruction of solar irradiance since 1610 – implications for climate-change, Geophys. Res. Lett., 22, 3195–3198, 1995. Meehl,~G A., Washington,~W M., Santer,~B D., Collins,~W D., Arblaster,~J M., Hu,~A X., Lawrence,~D M., Teng,~H Y., Buja,~L E., and Strand,~W G.: Climate change projections for the twenty-first century and climate change commitment in the CCSM3, J. Climate, 19, 2597–2616, 2006. Moros,~M., Emeis,~K., Risebrobakken,~B., Snowball,~I., Kuijpers,~A., McManus, ~J., and Jansen,~E.: Sea surface temperatures and ice rafting in the Holocene North Atlantic: climate influences on Northern Europe and Greenland, Quaternary Sci. Rev., 23, 2113–2126, \doi10.1016/j.quascirev.2004.08.003, 2004. Mudelsee,~M.: Ramp function regression: A~tool for quantifying climate transitions, Comput. Geosci., 26, 293–307, 2000. Oleson,~K W., Dai,~Y., Bonan,~G., Rosilovich,~M., Dickinson,~R., Dirmeyer,~P., Hoffman,~F., Houser,~P., Levis,~S., Niu,~G.-Y., Thornton,~P., Vertenstein,~M., Yang,~Z.-L., and Zeng,~X.: Technical description of the Community Land Model (CLM), NCAR Tech. Note, NCAR/TN-461+STR, 173~pp., 2004. Schmittner,~A., Saenko,~O A., and Weaver,~A J.: Coupling of the hemispheres in observations and simulations of glacial climate change, Quaternary Sci. Rev., 22, 659–671, 2003. Smith,~R S. and Gent,~P R.: Reference manual for the Parallel Ocean Program (POP), ocean component of the Community Climate System Model (CCSM2.0 and 3.0), Los Alamos National Laboratory Tech. Rep. LA-UR-02-2484, 75~pp., 2004. Steinhilber,~F., Beer,~J., and Fröhlich,~C.: Total solar irradiance during the Holocene, Geophys. Res. Lett., 36, L19 704, \doi10.1029/2009GL040142, 2009. Stenchikov,~G., Hamilton,~K., Stouffer,~R J., Robock,~A., Ramaswamy,~V., Santer,~B., and Graf,~H F.: Arctic Oscillation response to volcanic eruptions in the IPCC AR4 climate models, J. Geophys. Res.-Atmos., 111, D07 107, \doi10.1029/2005JD006286, 2006. Stenchikov,~G., Delworth,~T L., Ramaswamy,~V., Stouffer,~R J., Wittenberg,~A., and Zeng,~F R.: Volcanic signals in oceans, J. Geophys. Res.-Atmos., 114, D16 104, \doi10.1029/2008JD011673, 2009. Stocker,~T F.: Past and future reorganizations in the climate system, Quaternary Sci. Rev., 19, 301–319, 2000. Sutton,~R T. and Hodson,~D L R.: Atlantic ocean forcing of North American and European summer climate, Science, 309, 115–118, \doi10.1126/science.1109496, 2005. Thompson,~A M., Butler,~J H., Daube,~B C., Dutton,~G S., Elkins,~J W., Hall,~B D., Hurst,~D F., King,~D B., Kline,~E S., Lafleur,~B G., Lind,~J., Lovitz,~S., Mondeel,~D J., Montzka,~S A., Moore,~F L., Nance,~J D., Neu,~J L., Romanshkin,~P A., Scheffer,~A., and Snible,~W J.: Halocarbons and other atmospheric trace species, in: Climate Monitoring and Diagnostics Laboratory, Summary Report No 27, 115–135, NOAA CMDL, Boulder, CO, 2004. Timmermann,~A., Latif,~M., Voss,~R., and Grotzner,~A.: Northern Hemispheric interdecadal variability: a coupled air-sea mode, J. Climate, 11, 1906–1931, 1998. van~der Schrier,~G., Weber,~S L., and Drijfhout,~S S.: Sea level changes in the North Atlantic by solar forcing and internal variability, Clim. Dynam., 19, 435–447, \doi10.1007/s00382-002-0235-y, 2002. Yeager,~S G., Shields,~C A., Large,~W G., and Hack,~J J.: The low-resolution CCSM3, J. Climate, 19, 2545–2566, 2006. Yoshimori,~M., Raible,~C C., Stocker,~T F., and Renold,~M.: Simulated decadal oscillations of the Atlantic meridional overturning circulation in a~cold climate state, Clim. Dynam., 34, 101–121, \doi10.1007/s00382-009-0540-9, 2010. Zorita,~E., von Storch,~H., Gonzalez-Rouco,~F J., Cubasch,~U., Luterbacher,~J., Legutke,~S., Fischer-Bruns,~I., and Schlese,~U.: Climate evolution in the last five centuries simulated by an atmosphere-ocean model: global temperatures, the North Atlantic Oscillation and the Late Maunder Minimum, Meteorol. Z., 13, 271–289, \doi10.1127/0941-2984/2004/0013-0271, 2004.