@article{fdi:010044323,
  title = {{C}ross-shelf structure of coastal upwelling : a two - dimensional extension of {E}kman's theory and a mechanism for inner shelf upwelling shut down},
  author = {{E}strade, {P}. and {M}archesiello, {P}atrick and {V}erdi{\`e}re de, {A}. {C}. and {R}oy, {C}laude},
  editor = {},
  language = {{ENG}},
  abstract = {{S}ea-surface temperature images of the coastal upwelling regions off {N}orthwest {A}frica show that the core of upwelling is sometimes located far from the coast. {T}his has been documented in three regions that share a common feature, namely a wide and shallow continental shelf. {T}his upwelling feature plays a key role in the ecology of the {C}anary {C}urrent {S}ystem. {I}t creates an innerfront which provides retention for biological material, e.g. fish eggs and larvae, in the highly productive nearshore environment. {A}n analytical model has been developed based on a two dimensional extension of {E}kman's {S}olution. {T}he linear and steady response of a homogeneous {O}cean forced by an upwelling-favorable wind provides a mechanism for the upwelling separation from the coast. {T}he merging of the {S}urface and bottom {E}kman layers induces a very weak cross-shore circulation and a "kinematic barrier" for the {E}kman transport divergence. {I}n the case of an alongshore wind, the barrier is located near the isobath h approximate to 0.4{D}, where {D} is the thickness of {E}kman layers. {T}his yields 1111 upwelling cell which is essentially concentrated in the region 0.5{D} < h < 1.25{D}, with upwelling occurring preferentially near the isobath h approximate to 0.6{D}. {I}t turns out that the cross-shore width of upwelling scales with {D}/{S}, the ratio of {E}kman depth to bottom topographic slope. {T}he application of this solution to real bathymetric profiles rationalizes, not only the offshore upwelling observations in {N}orthwest {A}frica, but also the influence of topography oil file cross-shelf structure of a wind-driven coastal upwelling. {T}he model also quantifies the effect of the cross-shore wind component showing how it drives the nearshore pressure gradient adjustment and how it affects the upwelling. {A} linear numerical experiment reproduces the theoretical steady solution, thereby allowing investigation of the transient regime. {R}elaxation of the hypothesis in the numerical model validates the linear assumption of the theory and then allows investigation of the sensitivity to friction parameterizations and the influence of stratification. {T}he latter leads to an "oscillation" of the upwelling cell with seaward migration driven by outcropping and homogeneization of the water column. and, coastal incursion driven by a "boundary layers splitting" process caused by shoreward advection of the isopycnal dome and stratification of the inner shelf.},
  keywords = {},
  booktitle = {},
  journal = {{J}ournal of {M}arine {R}esearch},
  volume = {66},
  numero = {5},
  pages = {589--616},
  ISSN = {0022-2402},
  year = {2008},
  DOI = {10.1357/002224008787536790},
  URL = {https://www.documentation.ird.fr/hor/fdi:010044323},
}