Offshore expansion of the Brazilian coastal upwelling zones during Marine Isotope Stage 5

Productivity Evolution in the South Brazilian Bight During the Last 40,000 Years

“…It has been suggested that those modern upwelling zones associated with the mesoscale of the BC would be the remnants of an even larger western boundary upwelling system along the western South Atlantic in the past (Lessa et al, ). Indeed, reconstructions of such upwelling system relying both on G. bulloides and G. glutinata abundances and on paleotemperature estimates over the last 140 cal kyr BP reiterate the impact of the BC dynamics on productivity changes reaching farther north (25–21°S) to our core site and encompassing both the Santos and Campos basins (Lessa et al, ; Portilho‐Ramos et al, ; Souto et al, ).…”

“…Being primarily herbivorous, they proliferate when nutrients are introduced in the euphotic zone (e.g., upwelling regions), favoring primary production (e.g., phytoplankton blooms) (Metcalfe et al, ; Ortiz et al, ; Schiebel & Hemleben, ). For this reason, both species are considered indicative of upwelling systems (Naidu et al, ; Peeters et al, ; Souto et al, ) and have been widely applied as proxies of marine productivity in paleoceanographic reconstructions (Lessa et al, ; Ortiz et al, ; Portilho‐Ramos et al, ).…”

“…It is also one of the regions where those nutrient‐enriched waters originated in the Southern Ocean emerge to the surface (Anderson et al, ). Nevertheless, especially in South Atlantic western boundary upwelling regions, where higher primary productivity occurs, paleoproductivity reconstructions are so far scarce or limited in temporal resolution and coverage (Lessa et al, ; Portilho‐Ramos et al, ; Souto et al, ). Therefore, the AMOC impact on marine productivity in the western South Atlantic still remains elusive.…”

The Impact of the AMOC Resumption in the Western South Atlantic Thermocline at the Onset of the Last Interglacial

“…The change from high to low G. inflata δ 13 C at the beginning of MIS 5e also suggests an intensified export of preformed nutrients to the thermocline, which likely accompanied a thickening of the SACW. The transition to the Last Interglacial is also marked by a noticeable increase in the relative abundance of planktonic foraminifera Globigerina bulloides (Lessa et al, ) (Figure f). G. bulloides is known for tracking high productivity conditions, mainly associated with seasonal upwelling (Peeters et al, ; Salgueiro et al, ; Tedesco et al, ).…”

“…G. bulloides is known for tracking high productivity conditions, mainly associated with seasonal upwelling (Peeters et al, ; Salgueiro et al, ; Tedesco et al, ). In the southeast Brazilian margin, a higher nutrient content in the SACW fueling the bottom of the mixed layer would favor the proliferation of G. bulloides in moments of SACW shoaling, but it would disrupt the optimal conditions for Globigerinoides ruber (Lessa et al, , ; Portilho‐Ramos et al, ). Thus, (1) high G. inflata δ 18 O, (2) a strong upper ocean stratification, (3) low G. inflata δ 13 C, and (4) the increase in the relative abundance of G. bulloides (and decrease in G. ruber ) suggest that the thermocline of the western South Atlantic was marked by a thicker and likely colder SACW in the earlier stages of the Last Interglacial (Figures c–f).…”