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

Author(s)

Paloczy, A. ; Brink, K. H. ; da Silveira, Ilson C. A. ; Arruda, Wilton Z. ; Martins, Renato P.

• Document type: Journal article
• Source: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS; v. 121, n. 7, p. 5134-5163, JUL 2016.
• Web of Science Citations: 4

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. (AU)

• FAPESP's process: 13/11465-4 - Coastal upwelling and South Atlantic Central Water (SACW) Intrusions in the Espírito Santo Basin (18°S-22°S)
• Grantee: André Palóczy Filho
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 14/03451-6 - Intrusions of South Atlantic Central Water onto the Espírito Santo basin shelf (18°S-22°S, Brazil)
• Grantee: André Palóczy Filho
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• FAPESP's process: 08/58101-9 - Impact of the Southwestern Atlantic Ocean on South American climate for the 20th and 21st centuries
• Grantee: Tercio Ambrizzi
• Support Opportunities: Research Program on Global Climate Change - Thematic Grants