The Plata plume water penetration into the southwestern Atlantic shelf during the Holocene

Abstract

On the southeastern South American shelf, the discharge of the Río de la Plata and those from the Uruguayan and southern Brazilian lagoons forms a low-salinity water mass named Plata Plume Water (PPW). The northward penetration of this water mass into the SW Atlantic presents a clear seasonal regime, determined more by the intensity of the southerly winds than by river discharge. In this sense, understanding the plume’s variation is a valuable tool for recognizing Holocene wind dynamics in the Southwest Atlantic. This study aims to identify the PPW’s onset and intensity variations on the southeastern South American shelf by analyzing the grain-size characteristics of the Holocene deposits of the southern Brazilian shelf. End-member modeling was used to recognize the sediment population representing the PPW input on the southeastern South American shelf. The results led us to recognize a silty population whose characteristic is coherent with the PPW input. Moreover, this grain size population presents a behavior that agrees with other independent proxies from other sediment cores in the same area, especially after ca. 2,800 cal BP, concurrent with establishing the late Holocene climatic and oceanographic conditions. Finally, we could recognize a ca. 300 years periodicity, similar to other works in the southern hemisphere, indicating that external (solar) forcing played an important role in the observed century-scale climate variability during the Holocene of the Southwest Atlantic.