HR: 1340h
AN: PP33A-1007 [Abstracts]
TI: Circulation Changes in the Southern Ocean During the Last Glacial Inception, Induced by an Atmospheric Coupling with the Northern Hemisphere
AU: Govin, A
EM: aline.govin@lsce.cnrs-gif.fr
AF: LSCE/IPSL, Laboratoire des Sciences du Climat et de l'Environnement (CEA-CNRS-
UVSQ), Domaine du CNRS, Avenue de la Terrasse, Gif sur Yvette, F-91190, France
AU: Govin, A
EM: aline.govin@lsce.cnrs-gif.fr
AF: BCCR, Bjerknes Centre for Climate Research, University of Bergen, Allegaten 55, Bergen,
5007, Norway
AU: * Labeyrie, L
EM: laurent.labeyrie@lsce.ipsl.fr
AF: LSCE/IPSL, Laboratoire des Sciences du Climat et de l'Environnement (CEA-CNRS-
UVSQ), Domaine du CNRS, Avenue de la Terrasse, Gif sur Yvette, F-91190, France
AU: * Labeyrie, L
EM: laurent.labeyrie@lsce.ipsl.fr
AF: IUF Departement de Physique UVSQ, Bat. Buffon 202 45 avenue des Etats Unis,
Versailles, F-78035, France
AU: Michel, E
EM: elisabeth.michel@lsce.cnrs-gif.fr
AF: LSCE/IPSL, Laboratoire des Sciences du Climat et de l'Environnement (CEA-CNRS-
UVSQ), Domaine du CNRS, Avenue de la Terrasse, Gif sur Yvette, F-91190, France
AU: Waelbroeck, C
EM: claire.waelbroeck@lsce.cnrs-gif.fr
AF: LSCE/IPSL, Laboratoire des Sciences du Climat et de l'Environnement (CEA-CNRS-
UVSQ), Domaine du CNRS, Avenue de la Terrasse, Gif sur Yvette, F-91190, France
AU: Dewilde, F
EM: fabien.dewilde@lsce.cnrs-gif.fr
AF: LSCE/IPSL, Laboratoire des Sciences du Climat et de l'Environnement (CEA-CNRS-
UVSQ), Domaine du CNRS, Avenue de la Terrasse, Gif sur Yvette, F-91190, France
AU: Jansen, E
EM: eystein.jansen@bjerknes.uib.no
AF: BCCR, Bjerknes Centre for Climate Research, University of Bergen, Allegaten 55, Bergen,
5007, Norway
AB:
The changes in the oceanic circulation at the initiation of the last glacial period, and its role in the chain of events
linking the decrease of Northern summer insolation with the establishment of large ice continental sheets and
global cooling are still poorly known. We present here new constraints on the deep-water circulation changes in
the Southern Ocean during the last glacial inception (130 – 60 ky), in relationship to surface hydrology and global
climatology.
We use high-resolution oxygen isotope composition (δ18O ) records measured on planktic and
benthic foraminifera, and carbon isotope composition of the benthic species Cibicides as a tracer of deep-
water ventilation. From the comparison of three marine sediment cores, we consider the three major water
masses of the Southern Ocean: Antarctic Intermediate Waters (AAIW) from core MD97-2120 (45°32S
174°56E 1210m) ( Pahnke et al. 2003; Pahnke and Zahn 2005) in the southwest Pacific sector;
Circumpolar Deep Waters (CDW) from the newly analyzed core MD02-2488 (46°29S, 88°01E, 3420
m) (this study) in the Indian sector of the Southern Ocean; and Antarctic Bottom Waters (AABW) from ODP site
1089 (41°S, 10°E, 4620m) ( Gersonde et al 1999; Hodell et al 2003; Mortyn et al 2003) in the South
Atlantic. The records are compared on a common timescale that we defined, based on the assumption that the
major temperatures changes occur simultaneously above Antarctica ( EPICA community members, 2004) and
in the subantarctic zone of the Southern Ocean.
The data show that surface coolings associated with Marine Isotope Stage (MIS) 5.5-5.4 and 5.1-4 transitions in
the high southern latitudes follow the 65°N summer insolation decrease and the northern ice-sheets
growth. Simultaneously, we observe two strong reductions of deep-water ventilation and one shift in intermediate
waters charcteristics in the Southern Ocean. This suggests a rapid coupling between the Southern Ocean deep
waters changes and the Northern Hemisphere climatology.
Comparison with North Atlantic core (SU90-08, 43°03 N, 30°02W, 3080 m) ( Grousset et al.,
1993), which shows active NADW formation throughout MIS 5, allows to discard the hypothesis of a deep ocean
coupling via NADW. The study of four additional cores from the Indian sector of the Southern Ocean suggests that
an atmospheric coupling between the Northern and Southern hemispheres could induce deep-water circulation
changes in the Southern Ocean.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4936 Interglacial
DE: 4938 Interhemispheric phasing
DE: 4940 Isotopic stage
DE: 4962 Thermohaline
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting