@article{fdi:010060870,
  title = {{I}nitialisation and predictability of the {AMOC} over the last 50 years in a climate model},
  author = {{S}wingedouw, {D}. and {M}ignot, {J}uliette and {L}abetoulle, {S}. and {G}uilyardi, {E}. and {M}adec, {G}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he mechanisms involved in {A}tlantic meridional overturning circulation ({AMOC}) decadal variability and predictability over the last 50 years are analysed in the {IPSL}-{CM}5{A}-{LR} model using historical and initialised simulations. {T}he initialisation procedure only uses nudging towards sea surface temperature anomalies with a physically based restoring coefficient. {W}hen compared to two independent {AMOC} reconstructions, both the historical and nudged ensemble simulations exhibit skill at reproducing {AMOC} variations from 1977 onwards, and in particular two maxima occurring respectively around 1978 and 1997. {W}e argue that one source of skill is related to the large {M}ount {A}gung volcanic eruption starting in 1963, which reset an internal 20-year variability cycle in the {N}orth {A}tlantic in the model. {T}his cycle involves the {E}ast {G}reenland {C}urrent intensity, and advection of active tracers along the subpolar gyre, which leads to an {AMOC} maximum around 15 years after the {M}ount {A}gung eruption. {T}he 1997 maximum occurs approximately 20 years after the former one. {T}he nudged simulations better reproduce this second maximum than the historical simulations. {T}his is due to the initialisation of a cooling of the convection sites in the 1980s under the effect of a persistent {N}orth {A}tlantic oscillation ({NAO}) positive phase, a feature not captured in the historical simulations. {H}ence we argue that the 20-year cycle excited by the 1963 {M}ount {A}gung eruption together with the {NAO} forcing both contributed to the 1990s {AMOC} maximum. {T}hese results support the existence of a 20-year cycle in the {N}orth {A}tlantic in the observations. {H}indcasts following the {CMIP}5 protocol are launched from a nudged simulation every 5 years for the 1960-2005 period. {T}hey exhibit significant correlation skill score as compared to an independent reconstruction of the {AMOC} from 4-year lead-time average. {T}his encouraging result is accompanied by increased correlation skills in reproducing the observed 2-m air temperature in the bordering regions of the {N}orth {A}tlantic as compared to non-initialized simulations. {T}o a lesser extent, predicted precipitation tends to correlate with the nudged simulation in the tropical {A}tlantic. {W}e argue that this skill is due to the initialisation and predictability of the {AMOC} in the present prediction system. {T}he mechanisms evidenced here support the idea of volcanic eruptions as a pacemaker for internal variability of the {AMOC}. {T}ogether with the existence of a 20-year cycle in the {N}orth {A}tlantic they propose a novel and complementary explanation for the {AMOC} variations over the last 50 years.},
  keywords = {{D}ecadal climate prediction ; {O}cean dynamics ; {A}tlantic meridional ; overturning circulation ; {H}indcast ; {P}redictability ; {V}olcanic eruptions ; {M}ount {A}gung ; {N}orth {A}tlantic oscillation ; {OCEAN} {ATLANTIQUE} ; {ATLANTIQUE} {NORD}},
  booktitle = {{P}resentation and analysis of the {IPSL} and {CNRM} climate models used in {CMIP}5},
  journal = {{C}limate {D}ynamics},
  volume = {40},
  numero = {9-10},
  pages = {2381--2399},
  ISSN = {0930-7575},
  year = {2013},
  DOI = {10.1007/s00382-012-1516-8},
  URL = {https://www.documentation.ird.fr/hor/fdi:010060870},
}