@article{fdi:010071330,
  title = {{R}econstructing extreme {AMOC} events through nudging of the ocean surface : a perfect model approach},
  author = {{O}rtega, {P}. and {G}uilyardi, {E}. and {S}wingedouw, {D}. and {M}ignot, {J}uliette and {N}guyen, {S}.},
  editor = {},
  language = {{ENG}},
  abstract = {{W}hile the {A}tlantic {M}eridional {O}verturning {C}irculation ({AMOC}) is thought to be a crucial component of the {N}orth {A}tlantic climate, past changes in its strength are challenging to quantify, and only limited information is available. {I}n this study, we use a perfect model approach with the {IPSL}-{CM}5{A}-{LR} model to assess the performance of several surface nudging techniques in reconstructing the variability of the {AMOC}. {S}pecial attention is given to the reproducibility of an extreme positive {AMOC} peak from a preindustrial control simulation. {N}udging includes standard relaxation techniques towards the sea surface temperature and salinity anomalies of this target control simulation, and/or the prescription of the wind-stress fields. {S}urface nudging approaches using standard fixed restoring terms succeed in reproducing most of the target {AMOC} variability, including the timing of the extreme event, but systematically underestimate its amplitude. {A} detailed analysis of the {AMOC} variability mechanisms reveals that the underestimation of the extreme {AMOC} maximum comes from a deficit in the formation of the dense water masses in the main convection region, located south of {I}celand in the model. {T}his issue is largely corrected after introducing a novel surface nudging approach, which uses a varying restoring coefficient that is proportional to the simulated mixed layer depth, which, in essence, keeps the restoring time scale constant. {T}his new technique substantially improves water mass transformation in the regions of convection, and in particular, the formation of the densest waters, which are key for the representation of the {AMOC} extreme. {I}t is therefore a promising strategy that may help to better constrain the {AMOC} variability and other ocean features in the models. {A}s this restoring technique only uses surface data, for which better and longer observations are available, it opens up opportunities for improved reconstructions of the {AMOC} over the last few decades.},
  keywords = {{D}ecadal variability ; {A}tlantic {M}eridional {O}verturning {C}irculation ; {S}urface nudging ; {C}oupled general circulation model ; {ATLANTIQUE}},
  booktitle = {},
  journal = {{C}limate {D}ynamics},
  volume = {49},
  numero = {9-10},
  pages = {3425--3441},
  ISSN = {0930-7575},
  year = {2017},
  DOI = {10.1007/s00382-017-3521-4},
  URL = {https://www.documentation.ird.fr/hor/fdi:010071330},
}