Changes in Holocene meridional circulation and poleward Atlantic flow: the Bay of Biscay as a nodal point

Type Article
Date 2017-03
Language English
Author(s) Mary Yannick1, Eynaud FrederiqueORCID1, Colin Christophe2, Rossignol Linda1, Brocheray Sandra1, Mojtahid Meryem3, Garcia Jennifer3, Peral Marion1, Howa HeleneORCID3, Zaragosi Sebastien1, Cremer Michel1
Affiliation(s) 1 : Univ Bordeaux, UMR 5805, Lab Environnements & Paleoenvironnements Ocean, F-33615 Pessac, France.
2 : Univ Paris 11, Lab Geosci, F-91405 Orsay, France.
3 : Univ Angers, UMR CNRS6112 LPG BIAF, Recent & Fossil Bio Indicators, 2 Bd Lavoisier, F-49045 Angers 01, France.
Source Climate Of The Past (1814-9324) (Copernicus Gesellschaft Mbh), 2017-03 , Vol. 13 , P. 201-216
DOI 10.5194/cp-13-201-2017
WOS© Times Cited 16
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 ffi 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.

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Mary Yannick, Eynaud Frederique, Colin Christophe, Rossignol Linda, Brocheray Sandra, Mojtahid Meryem, Garcia Jennifer, Peral Marion, Howa Helene, Zaragosi Sebastien, Cremer Michel (2017). Changes in Holocene meridional circulation and poleward Atlantic flow: the Bay of Biscay as a nodal point. Climate Of The Past, 13, 201-216. Publisher's official version : https://doi.org/10.5194/cp-13-201-2017 , Open Access version : https://archimer.ifremer.fr/doc/00420/53177/