Multiple jets in the Malvinas Current

PIOLA, A. R.; FRANCO, B. C.; PALMA, E. D.

Foz do Iguacu

Congreso; 2010 Meeting of the Americas; 2010

American Geophysical Union

Downstream of Drake Passage, the northern portion of the Antarctic Circumpolar Current (ACC) describes a sharp anticyclonic turn causing the northward penetration of Subantarctic and Antarctic waters into the western Argentine Basin to around 38°S. This branch of the ACC, the Malvinas Current (MC), is the northernmost penetration of subpolar waters in the Southern Hemisphere and may be a significant source of nutrients, presumably triggering the development and maintenance of intense chlorophyll blooms throughout the western South Atlantic. A recent analysis of eighteen year of sea surface temperature data indicates that the MC is characterized by a series of surface fronts created by two or more cold branches flowing approximately parallel to the continental slope of the Argentine Basin. The present study, based on the analysis of historical hydrographic data, surface drifters and deep floats, satellite derived sea surface temperature, color and altimetry, shows that the MC is organized as a series of distinct jets. The multiple jet structure is also evident in satellite derived surface dynamic topography. Geostrophic velocity and acoustic Doppler current profiler cross sections reveal the jets do not necessarily reach the ocean surface and may extend several hundred meters in the vertical. It has recently been suggested that the interaction of the deep water mass structure and associated flows with unconsolidated sediments and local tectonic influences in the geological past may have modified the margin morphology, characterized by a complex terraced slope in the southern Argentine margin. Our data and highly simplified numerical simulations suggests that variations in the bottom slope, caused by these erosive  and depositional features, may be responsible for the maintenance of the multiple jet structure of the MC system in the present ocean.