INFLUÊNCIA DE VÓRTICES NA CONCENTRAÇÃO DE CLOROFILA DA CONFLUÊNCIA BRASIL-MALVINAS: MECANISMOS INFERIDOS POR SENSORIAMENTO REMOTO

Abstract

This study aims to (a) identify the spatial patterns in the surface phytoplankton abundance, here indexed as satellite chlorophyll-a concentration ([chla]), associated with mesoscale eddies of the Brazil-Malvinas Confluence (BMC) and (b) infer which are the physical mechanisms responsible for such patterns. In this work, the 57 largest eddies in the broad BMC region were selected from a global eddy dataset based on merged satellite altimetry data. Using those eddies, the main mechanisms which may eddies affect the [chla] were tested: (a) the eddy-pumping, (b) the eddy Ekman pumping and (c) the eddy advection of meridional [chla] gradients. Mean spatial chlorophyll and chlorophyll patterns associated with the selected eddies, as well as correlations between variables that describe the [chla], and its spatial anomalies (Δ[chla]), distribution and the eddies’ physical characteristics, were calculated. Positive and negative anomalies associated with cyclonic and anticyclonic eddies’ interiors, respectively, and significant inverse correlations between eddies’ amplitudes and the difference between Δ[chla] inside and outside the eddies, were found as evidence of eddy-pumping mechanism. The [chla] spatial pattern associated to the eddy advection of meridional gradients was evident in the eastern side of the features, as low (high) [chla] being advected from south (north) in anticyclonic (cyclonic) eddies. The magnitude of the difference between Δ[chla] in the east and west eddies’ hemispheres presented itself more dependent on the [chla] meridional gradient intensity than on the eddy rotational velocity. Furthermore, the non-linear parameter of the studied eddies suggest that BCM eddies are capable to transport the water parcels trapped inside them, helping in the propagation of the eddy-pumping signature.