Topographic gyres, coastal jets and fronts in the Northpatagonian Gulfs

PALMA, ELBIO DANIEL; TONINI MARIANO HERNAN

Bahía Blanca

Congreso; Science and Management of Estuaries and Coast: A tale of two Hemisphere (ECSA44); 2008

Instituto Argentino de Oceanografía - IADO

The influence of tidal forcing, heat fluxes and tidal and wind mixing on the circulation and stratification near Valdes Peninsula (VP) and adjacent regions of the San Matias Gulf (SMG) is examined using a 3D high- resolution baroclinic ocean model. In the control run the model is forced by tides and monthly climatological fields of wind stress and heat fluxes. Additional sensitivity experiments include variations in bottom topography and forcing fields. It is found that the tide plays an importatn role in regulating the annual cycle of the circulation in SMG. The overall circulation pattern inside the Gulf is dominated by a strong cyclonic gyre during summer with smaller anticyclonic gyres on the west coast and north of VP. The spinup of the cyclonic circulation between September and January is likely caused by the interaction of the tides and stratification (generated by surface heat fluxes) in the presence of variable topography. From December to March the cyclonic circulation continues to strenghten but gradually shrinks in size towards the south. When winter erodes the stratification, the cyclonic circulation quickly spins down and the interior of the Gulf is occupied by an anticyclonic gyre. The model results are qualitatively consistent with circulation patterns based on hydrographic observations and previous low-resolution models of the region. The model also exhibits tidal mixing fronts following the 60m isobath northeast of VP and particulary over the SMG mouth. Changes in wind intensity deepens the termocline and move the VP front offshore.