@article{fdi:010074525,
  title = {{S}easonal phasing of {A}gulhas {C}urrent transport tied to a baroclinic adjustment of near-field winds},
  author = {{H}utchinson, {K}. and {B}eal, {L}. {M}. and {P}enven, {P}ierrick and {A}nsorge, {I}. and {H}ermes, {J}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he {A}gulhas {C}urrent plays a significant role in both local and global ocean circulation and climate regulation, yet the mechanisms that determine the seasonal cycle of the current remain unclear, with discrepancies between ocean models and observations. {O}bservations from moorings across the current and a 22-year proxy of {A}gulhas {C}urrent volume transport reveal that the current is over 25% stronger in austral summer than in winter. {W}e hypothesize that winds over the {S}outhern {I}ndian {O}cean play a critical role in determining this seasonal phasing through barotropic and first baroclinic mode adjustments and communication to the western boundary via {R}ossby waves. {O}ur hypothesis is explored using single-layer and one-and-a-half layer models. {W}e find that the barotropic contribution to seasonal phasing is small, with the majority of the seasonal signal deflected offshore and along the {M}ozambique {R}idge. {T}he summertime maximum and wintertime minimum can, however, be reproduced by a one-and-a-half layer reduced gravity model in which adjustment time to wind forcing via {R}ossby waves is in line with observations from satellite altimetry. {A}dditionally, near-field winds (to the west of 35 degrees {E}) are shown to have a controlling influence on the seasonal phasing, as signals from farther afield dissipate through destructive interference with overlying winds before reaching the western boundary. {T}hese results suggest a critical role for a baroclinic adjustment to near-field winds in setting the summertime maximum in {A}gulhas {C}urrent transport. {T}he {A}gulhas {C}urrent flows along the east coast of {S}outh {A}frica, transporting warm {I}ndian {O}cean water southward, acting as a vital limb of the global ocean conveyor belt and influencing local rainfall and climate. {T}his study looks at the seasonal cycle of the {A}gulhas {C}urrent and uses idealized models to explore how winds over the {S}outhern {I}ndian {O}cean may influence this seasonality. {T}he current is 25% stronger in summertime, yet we do not have existing knowledge regarding the principal drivers that set this observed variability. {I}n this study, we find that baroclinic processes communicating the wind stress curl variability from near-field winds have a dominant contribution to the seasonal phasing. {W}ind signals from further afield are found to die out during their journey west and so have little effect on the seasonal cycle of the {A}gulhas {C}urrent. {F}urthermore, correctly capturing the adjustment time to wind forcing is found to be very important when endeavoring to simulate the {A}gulhas {C}urrent seasonal phasing using a reduced gravity model. {T}his study exposes a link between the seasonality of {A}gulhas {C}urrent and propagation of first baroclinic mode {R}ossby waves communicating the near-field wind stress signal across the western portion of the {S}outhern {I}ndian {O}cean.},
  keywords = {{A}gulhas {C}urrent ; seasonal cycle ; wind stress curl ; {R}ossby waves ; {I}ndian {O}cean ; reduced gravity model ; {OCEAN} {INDIEN} ; {AGULHAS} {COURANT}},
  booktitle = {},
  journal = {{J}ournal of {G}eophysical {R}esearch : {O}ceans},
  volume = {123},
  numero = {10},
  pages = {7067--7083},
  ISSN = {2169-9275},
  year = {2018},
  DOI = {10.1029/2018jc014319},
  URL = {https://www.documentation.ird.fr/hor/fdi:010074525},
}