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Bottom Boundary Layer and Particle Dynamics in an Upwelling Affected Continental Margin (NW Iberia)
Author(s) -
VillacierosRobineau Nicolás,
Zúñiga Diana,
BarreiroGonzález Beatriz,
AlonsoPérez Fernando,
Granda Francisco,
Froján María,
Collins Curtis A.,
Barton Eric Desmond,
Castro Carmen González
Publication year - 2019
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1029/2019jc015619
Subject(s) - downwelling , geology , upwelling , oceanography , continental shelf , hydrography , nepheloid layer , submarine pipeline , continental margin , boundary current , isopycnal , geophysics , ocean current , paleontology , tectonics , water column
The dynamics of the bottom boundary layer and their effects on the development of nepheloid layers (NLs) on a high‐energy and upwelling‐affected margin, the NW Iberian continental shelf, were studied by means of ADP currents, wave time series, and across‐shelf hydrographic surveys covering an entire annual cycle. The bottom boundary layer hydrodynamics showed that high levels of bottom shear stress over the inner shelf occurred mainly during downwelling seasons, when there was a coupling between storm waves and intense currents. This wave‐current coupling promotes strong resuspension events that favored the generation of bottom NLs (BNLs). BNLs were well developed on the inner continental shelf inshore of a thermohaline front generated by the interaction of the Iberian Poleward Current and the West Iberian Buoyant Plume. The existence of this front limited the extent of offshore export of resuspended particles during the downwelling season. In contrast, during the upwelling season, only thin BNLs were developed, and surface NLs, principally composed by biogenic particulate material, were advected offshore in the Ekman layer, often as part of the development of upwelling filaments. Our study confirmed that wave orbital velocity under stormy conditions, in combination with the hydrography, could explain the shoreward boundary of the Galician mud depocenter.