Coccolithophore and foraminifera paleoproductivity changes related to wind-driven upwellings in the SE Pacific since the LGM

S. Duchamp-Alphonse (1) , Giuseppe Siani (1) , Luc L Beaufort (2) , Elisabeth Michel (3) , Gulaye Isguder (3) , Frank Pérochon (1) , Alissia Rieux (1)

1 IDES - Interactions et dynamique des environnements de surface
2 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement
3 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]

Since the LGM, model calculations have emphasized the central role of the Southern Ocean (SO) as a key component of the global climate system. It is proposed that latitudinal shifts and intensity variations of the Southern Western Winds (SWW) would have significantly influenced the CO2 exchanges in the Ocean-Atmosphere system, regulating i) the ocean's deep ventilation (water stratification vs. upwellings); ii) the biological pump (primary production) ; and/or iii) sea ice extent. As the SWW are in part driven by the latitudinal thermal gradients, most palaeoceanographic inference on their activity in the past, are based on sea surface temperatures. Limited empirical evidences highlight upwelling intensity and ocean productivity changes associated to movement of oceanic fronts. The aim of this study is to infer the changes in the primary production and the wind-driven upwellings of the southeastern Pacific since the LGM, focusing on coccolithophore and planktic foraminifera assemblages of a CALYPSO piston core (MD07-3088), collected off the south Chilean margin (46°04.30'S; 1536m). It will help assessing changes in the oceanic front dynamic of the SWW-SO coupled system, for a better understanding of the global atmospheric CO2 variations. The MD07-3088 core benefits a robust chronology that has been assessed by a previous detailed tephrostratigraphy study supported by 23 AMS 14 C dating and a high-resolution δ18O stratigraphy. The preliminary records including CaCO3 contents, coccolith absolute and relative abundances and foraminifera absolute abundances, document enhanced coccolith and foraminifer abundances during the Last Glacial/Interglacial Transition (LGIT), probably tied to enhanced wind-driven upwellings.

Domaines: Climatologie

S. Duchamp-Alphonse, Giuseppe Siani, Luc L Beaufort, Elisabeth Michel, Gulaye Isguder, et al.. Coccolithophore and foraminifera paleoproductivity changes related to wind-driven upwellings in the SE Pacific since the LGM. 11th International Conference on Paleoceanography, Sep 2013, Barcelona, Spain. ⟨hal-01464684⟩