StabilityoftheClimateSystemandExtremeClimatesinModelExperiments.DissertationzurErlangungdesDoktorgradesderNaturwissenschaftenamFachbereichGeowissenschaftenderUniversit¨atBremenvorgelegt vonVanyaRomanovaBremen,2004Tag des Promotionskolloquiums:16.12.2004Gutachter:1. Prof. Dr. MichaelSchulz2. Prof. Dr. GerritLohmannPrufer¨ :1. Prof. Dr. KatrinHuhn2. Prof. Dr. J¨ornBleck-NeuhausEachofusvisitsthatEarthinvoluntarilyandwithoutaninvitation. Forme,itisenoughtowonderatitssecrets.AlbertEinstein(Quoted in Des MacHale, Wisdom (London, 2002))AbstractThepresentthesisexamines theocean andatmosphericdynamicsofpresent-dayclimateandLast Glacial Maximum (LGM) throughOcean andAtmosphere General Circulationmodels. Simulatingtheglacial climate differentLGMreconstructionsofseasurfacetem-peratures (SST) and sea-ice margins are used as forcing fields for the models: CLIMAP(1981), a modification of CLIMAP (1981), with additional cooling in the tropics, andreconstructionsasproducedfromWeinelt et al. (1996) andGLAMAP 2000, whichshowseasonallyicefreeconditionsintheNordicseas. Thestabilityofthethermohalinecircula-tions(THC)underdifferentreconstructionsisinvestigatedtogetherwiththecorrespondingatmosphericdynamics. Thestabilityanalysis,bymeansoffreshwaterfluxhysteresismapsrevealsmono-stabilityforeachglacialbackgroundstate,whichappearstobearobustfea-tureoftheglacialocean.