Changes in Holocene meridional circulation and poleward Atlantic flow: the Bay of Biscay as a nodal point
- 1Laboratoire Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), UMR 5805, Université de Bordeaux, 33615 Pessac, France
- 2Laboratoire Géosciences, Université de Paris-Sud, 91405 Orsay CEDEX, France
- 3UMR CNRS6112 LPG-BIAF, Recent and Fossil Bio-Indicators, Angers University, 2 Bd Lavoisier, 49045 Angers CEDEX 01, France
- anow at: Institut Polytechnique LaSalle-Beauvais, Dpt Géosciences, 19 rue Pierre Waguet, BP 30313, 60026 Beauvais, France
- bnow at: Laboratoire des Sciences du Climat et de l'Environnement (LSCE-IPSL), Domaine du CNRS, bât.12, 91198 Gif-sur-Yvette, France
Abstract. This paper documents the evolution over the last 10 kyr of one of the key parameters of climate: sea-surface temperatures (SSTs) in the North Atlantic. We focus on the southern Bay of Biscay, a highly sensitive oceanographic area regarding the dynamics of the North Atlantic subpolar and subtropical gyres (SPG and STG respectively). This site furthermore offers unique sedimentary environments characterized by exceptional accumulation rates, enabling the study of Holocene archives at (infra)centennial scales. Our results mainly derive from planktonic foraminiferal association analysis on two cores from the southern Landes Plateau. These associations are used as the basis of modern analogue technique transfer functions to track past hydrographical changes. SST reconstructions were thus obtained at an exceptional resolution and compared to a compilation of Holocene records from the northeastern North Atlantic. From this regional perspective are shown fundamental timing differences between the gyre dynamics, nuancing classical views of a simple meridional overturning cell. Our study highlights that western Europe underwent significant oscillations of (annual) SST during the last 10 kyr. During well-known intervals of mild boreal climate, warm shifts of more than 3 °C per century are accurately concomitant with positive sea-surface temperature anomalies and rise of micropalaeontological indicators of gyre dynamics in the northern North Atlantic, pointing to periods of greater intensity of the North Atlantic Current (SPG cell especially). Conversely, the SST signal records short-term cold anomalies which could be related to weaker SPG dynamics.