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Palóczy, A, Brink KH, da Silveira ICA, Arruda WZ, Martins RP.  2016.  Pathways and mechanisms of offshore water intrusions on the Espírito Santo Basin shelf (18°S–22°S, Brazil). Journal of Geophysical Research: Oceans. 121:5134–5163.   10.1002/2015JC011468   AbstractWebsite

The pathways and physical mechanisms associated with intrusions of cold, nutrient‐rich South Atlantic Central Water (SACW) on the continental shelf of the Espírito Santo Basin (ESB), off southeast Brazil (18°S–22°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 Tubarão Bight (TB, 19.5°S–22°S). These pathways are found to be locations where an equatorward along‐isobath pressure gradient force (PGFy*) of O(10-6 m s-2) develops in response to steady wind forcing. This equatorward PGFy* 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) PGFy* 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 ~0.3–0.5. In addition, the planetary β‐effect is related to a background equatorward PGFy*. 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.

Palóczy, A, da Silveira ICA, Castro BM, Calado L.  2014.  Coastal upwelling off Cape São Tomé (22°S, Brazil): The supporting role of deep ocean processes. Continental Shelf Research. 89:38-50.   AbstractWebsite

The regional ocean off Cape São Tomé (CST, 22°S, Brazil) is known to feature transient coastal upwelling and intense mesoscale activity associated with the Brazil Current (BC). Satellite and in situ observations are used to characterize the coastal upwelling and the oceanic pycnocline water intrusions onto the continental shelf. Coastal upwelling events around CST are found to be less intense than the ones around Cape Frio (23°S), confirming previously reported findings. It is shown that the quasi-standing growth of a BC cyclonic meander is an effective supporting mechanism to this primarily wind-driven coastal upwelling system. A typical propagating cyclonic meander event is described and compared with its quasi-standing counterpart. The propagating cyclones also appear to promote oceanic pycnocline water intrusions, but at a lesser extent than the quasi-standing features. The supporting effect of the BC cyclones was quantified via simplified numerical experiments carried out with a 2D, primitive-equation numerical model. It is shown that meanders enhance intrusions as they grow, and may decrease by ≈50% the momentum input needed from the wind to cause coastal upwelling. Also, the role of the sloping of the isolines linked to the mean baroclinic structure of the Brazil Current is examined in idealized numerical experiments. This structure is shown to be sufficient to explain the observed time scales of coastal upwelling. The kind of meander-driven intrusion investigated here appears to be a regional singularity of the CST region, and may provide insight into the cross-shelf dynamics of other Western Boundary Current regions where similar quasi-standing instabilities exist.