@article{PAR00002487,
  title = {{D}ecadal variations in equatorial {P}acific ecosystems and ferrocline/pycnocline decoupling - art. no. {GB}2019},
  author = {{R}odgers, {K}. {B}. and {A}umont, {O}livier and {M}enk{\`e}s, {C}hristophe and {G}orgues, {T}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he equatorial {P}acific {O}cean is known for its large interannual to decadal variability in circulation. {I}n particular, the changes that occurred in 1976/1977 have received considerable attention in the climate dynamics literature, and recently there has been much attention focused on changes that may have occurred there in 1997/1998. {U}nfortunately, because of data sparsity, the impact of these changes or shifts on ocean biogeochemistry and ecosystems remains largely unknown. {H}ere a three-dimensional ocean circulation model (the {ORCA}2 configuration of {OPA}) which has a food web/ biogeochemistry model ({PISCES}) embedded in it, and which has been forced with both {NCEP}-1 and {ERA}-40 reanalysis fluxes over multiple decades, is used as a tool to investigate decadal changes and their associated mechanisms. {O}ur main finding with the model is that a decrease in the amplitude of the surface zonal wind stress in the tropical {P}acific in the mid-to-late-1970s leads to a decrease in {F}e and {C}hl concentrations in the upwelling regions of the eastern equatorial {P}acific after 1976/ 1977. {T}hese changes find expression predominantly during the upwelling season (the seasonal maximum for {F}e and {C}hl concentrations), when surface {F}e and {C}hl concentrations tend to be significantly higher pre-1976/1977 than post-1976/1977. {T}he changes in {C}hl concentrations need to be understood as modulations of the amplitude of the seasonal cycle, rather than as a "biological regime shift' (an abrupt transition from one mean state to another). {I}n contrast to what is found for {F}e and {C}hl, for {NO}3 the decadal changes in surface concentrations in the upwelling region about 1976/1977 can be described as a shift in the mean state. {I}t is shown that the response in surface {F}e and {C}hl in the upwelling region about 1976/1977 is proportionally larger than the decadal changes in surface wind stress forcing, and it is also larger than the previously reported change in the strength of the meridional overturning strength of the subtropical cells ({STC}s). {I}mportantly, this amplified response reflects a decoupling of the ferrocline and pycnocline within the equatorial {P}acific. {I}n this way, the presence of a time-invariant sediment source for {F}e can substantially amplify the ecosystem response to decadal variability in ocean circulation.},
  keywords = {{PACIFIQUE} ; {ZONE} {EQUATORIALE}},
  booktitle = {},
  journal = {{G}lobal {B}iogeochemical {C}ycles},
  volume = {22},
  numero = {2},
  pages = {{NIL}_17--{NIL}_32},
  ISSN = {0886-6236},
  year = {2008},
  DOI = {10.1029/2006{GB}002919},
  URL = {https://www.documentation.ird.fr/hor/{PAR}00002487},
}