Malvinas Current at 40°S-41°S: First Assessment of Temperature and Salinity Temporal Variability

PIOLA, ALBERTO R.; FERRARI, RAMIRO; PANIAGUA, GUILLERMINA F.; GUERRERO, RAÚL; LAGO, LORELEY; SARACENO, MARTIN; PROVOST, CHRISTINE; ARTANA, CAMILA I.

JOURNAL OF GEOPHYSICAL RESEARCH

American Goephysical Union

Lugar: West Sussex; Año: 2018 vol. 123 p. 1 - 18

2169-9291

The temporal variability of 11 months of in situ velocity, temperature, and salinity data collectedat five moorings deployed at 408S?418S across the shelf-break in the Southwestern Atlantic is analyzed.Two distinct regimes characterized by strong and weak along-slope velocities are present. During thestrong regime the Malvinas Current flows northward through the moorings while during the nearly 5months long weak regime reversals of the along-slope velocities are frequently observed. Comparison withthe previous in situ time series obtained in the same region shows that such an extended period of weakflow has not been previously observed. During the weak regime, Sub-Antarctic Mode Water is observedover the 1,800 m isobath at an average depth of 500 m. Water masses occupying the upper 1,600 m duringthe strong regime deepen and shift eastward during the weak period. Satellite geostrophic velocities andsea surface temperature clearly show that the weak regime is due to a deflection to the east of the MalvinasCurrent, upstream of the mooring position. Analysis of the vertical structure of the currents indicate thatduring the weak regime the flow weakens mostly at the surface and presents a very small vertical shear. Incontrast, during the strong regime currents are surface-intensified. The change in the structure of the currentsat the mooring location impacts the relationship between in situ and altimetry-derived currents: duringthe weak regime altimetry adequately represents (rmsd 12 cm/s) in situ currents in the whole watercolumn, while during strong regime rmsd are larger than 15 cm/s below 600 m depth.