Pathways and mechanisms of offshore water intrusions on the Espirito Santo Basin shelf (18 degrees S-22 degrees S, Brazil)

TitlePathways and mechanisms of offshore water intrusions on the Espirito Santo Basin shelf (18 degrees S-22 degrees S, Brazil)
Publication TypeJournal Article
Year of Publication2016
AuthorsPaloczy A., Brink K.H, da Silveira I.CA, Arruda W.Z, Martins R.P
JournalJournal of Geophysical Research-Oceans
Volume121
Pagination5134-5163
Date Published2016/07
Type of ArticleArticle
ISBN Number2169-9275
Accession NumberWOS:000383468500042
Keywords22-degrees-s; arrested topographic wave; Brazil Current; Central Water; Coastal dynamics; continental-shelf; cross-shelf transport; deep-ocean forcing; east china sea; momentum flux; pressure-gradient; sao tome; seasonal; South Atlantic; south-atlantic; variability; vitoria eddy; western boundary current
Abstract

The pathways and physical mechanisms associated with intrusions of cold, nutrient-rich South Atlantic Central Water (SACW) on the continental shelf of the Espirito Santo Basin (ESB), off southeast Brazil (18 degrees S-22 degrees S), are investigated. To this end, a set of process-oriented, Primitive-Equation (PE) numerical models are used, together with an independent and more complete PE model, available observations and simple theoretical ideas. SACW enters the model ESB shelf mostly through two preferential pathways along the TubarAo Bight (TB, 19.5 degrees S-22 degrees S). These pathways are found to be locations where an equatorward along-isobath pressure gradient force (PGF(y*)) of O(10-6 m s(-2)) develops in response to steady wind forcing. This equatorward PGF(y*) is essentially in geostrophic balance, inducing onshore flow across the shelf edge, and most of the shelf proper. The Brazil Current (BC) imparts an additional periodic (in the along-shelf direction) PGF(y*) on the shelf. The intrinsic pycnocline uplifting effect of the BC in making colder water available at the shelf edge is quantified. The BC also induces local intrusions by inertially overshooting the shelf edge, consistent with estimated Rossby numbers of approximate to 0.3-0.5. In addition, the planetary -effect is related to a background equatorward PGF(y*). A modified Arrested Topographic Wave model is shown to be a plausible rationalization for the shelf-wide spreading of the pressure field imparted by the BC at the shelf edge. The deep-ocean processes examined here are found to enhance the onshore transport of SACW, while wind forcing is found to dominate it at leading order.

DOI10.1002/2015jc011468
Short TitleJ Geophys Res-Oceans
Student Publication: 
Yes