The Malvinas Current System from 25 years of MERCATOR-Ocean Operational Reanalysis: Fronts, Recirculation Cells, Vertical Motions and Blocking Events

J.M. LELLOUCHE; ZOÉ KOENIG; PIOLA, ALBERTO R.; Y-H. PARK; NATHALIE SENNÉCHAEL; MARTIN SARACENO; ARTANA, CAMILA; GARRIC, GILLES; FERRARI, RAMIRO

Congreso; 25 Years of Progress in Radar Altimetry Symposium,; 2018

Daily outputs from the Mercator-ocean (1/12°) globaloperational reanalysis are analyzed in the MalvinasCurrent (MC) system. The performance of the model isevaluated over the last 25 years using satellite altimetry,Argo float and mooring data. Model outputs arecompared to in situ mooring time series of velocity,temperature and salinity gathered over the PatagonianShelf break at 41°S (at three different times:1993-1995,2001-2003 and 2014-2015) and at 44.7°S (2015-2017).Comparisons show that the model reproduces correctlythe general circulation and the complex hydrographicfeatures of the study area including the vicinity of theBrazil-Malvinas Confluence. The model accuratelymatches the observations.The model outputs are then used to examine thesignature in potential density at 450 m and in absolutedynamic topography (ADT) of the major fronts of the MCSystem. We identify isolines of ADT and potentialdensity at 450 m associated to the mean front locationand establish their correspondence to specific watermass boundaries. Frontal displacements as depicted insatellite ADT, model ADT and model potential density at450 m along the MC present a remarkable agreement.The potential density field at 450 m is an excellentindicator for the synoptic mapping of the MC systemfronts. It makes possible the detection and tracking ofeddies shed by Polar Front that feed the MC and have amuch weaker signal in the ADT. The cyclonic eddies shedby the Polar Front contribute to the variability of the MCat 41°S and to the MC recirculation cell.The density field is sensitive to horizontal and verticalmotions of the water column. Empirical orthogonalfunctions of density and velocity fields of model outputsshow the relationship between the water massdistribution of the water column and the intensity of theMC during upwelling and downwelling events on thecontinental slope.Blockings events of the MC at 48°S are a recurrentfeature of the MC circulation (about 26 events over the25 year altimetry record, Artana et al., 2016). Duringthese events the MC downstream does not collapserather becomes the western boundary of a robustrecirculating cyclonic cell. Model outputs document thegenesis and the vertical structure of the blocking events.