International audienceThe Brazil Current (BC) is a relevant feature in the Atlantic Meridional Overturning Circulation (AMOC). Its behavior during slowdown or intense AMOC remains poorly known because of the lack of paleoceanographic records, especially for the Holocene. Here, we investigate changes in a western boundary upwelling system (Cabo Frio, off Southeastern Brazil) which are driven by variations in the BC and NE winds during the last 9 kyr. To assess the variability of the BC, we used δ¹⁸O, Mg/Ca, and assemblages of planktonic foraminifera. Our results indicate five oceanographic phases during the last 9 kyr. During Phase I (from 9.0 to 7.0 cal kyr BP), the BC diverged offshore from the modern upwelling area because of the low sea level, increasing the influence of shelf waters and coastal upwelling plumes on foraminifera assemblages. Phase II (7.0-5.0 kyr BP) was marked by the approach of the internal front of the BC with low intensity and episodes of strong productivity that were linked primarily to the upwelling of the South Atlantic Central Water (SACW) and/or Subpolar Shelf Waters (SPSWs) (cold). Phase III (5.0-3.5 kyr BP) was a transition, marking a large oceanographic and climatic change from the weakening of the AMOC. The internal front of the BC became warm and subsurface SACW upwelling was stronger. In Phase IV (3.5-2.5 kyr BP), the BC acquired its modern dynamics, but weak NE winds weakened the SACW's contribution to upwelling events. Finally, in Phase V (last 2.5 kyr BP), the NE winds reintensified, promoting frequent episodes of upwelling and intrusion by SPSWs during the Medieval Climate Anomaly

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[1] The mechanisms controlling subsurface temperature variability on the outer shelf in a western boundary upwelling system are quantified using observations from a mooring deployed off Cabo Frio, Brazil. Results from a multiple linear regression analysis reveal that, in addition to low-frequency variations associated with the seasonal evolution of temperature, the dominant mechanisms controlling temperature variability are wind stress curldriven upwelling, cross-isobath transport, the proximity of the Brazil Current to the shelf break, and perhaps changes in the strength of tidal mixing associated with the springneap cycle. The influence of the proximity of the Brazil Current decreases strongly with depth, being restricted to the top 80 m. Regression coefficients indicate that the relative contributions from the different forcings are roughly similar and that no single process has a dominant role explaining temperature variability near the shelf break. These suggest that successful modeling efforts in the region must adequately represent each of those processes.Citation: Belem, A. L., R. M. Castelao, and A. L. Albuquerque (2013), Controls of subsurface temperature variability in a western boundary upwelling system, Geophys. Res. Lett., 40,

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