Air-sea temperature decoupling in Western Europe during ... · winter (Pann

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Air-sea temperature decoupling in Western Europe during the last interglacial/glacial

transition

María Fernanda Sánchez Goñi, Edouard Bard, Amaelle Landais, Linda Rossignol, Francesco

d’Errico

Supplementary Information

Present-day environmental setting

At present, the western European margin is primarily affected by the strength and

direction of the northwesterlies and the North Atlantic subtropical gyre dynamic 1. The

western Iberian margin is locally influenced in summer by upwelling events that generate a

southward surface circulation while downwelling in winter develops a northward surface

circulation 2-3. At latitudes above 40°N, the atmospheric configuration results in year-round

wet climate, with annual precipitation at ~1000 mm, and a mean annual temperature of

10°C allowing for the development of the Atlantic mixed Quercus (oak) forest 4. In

southwestern Iberia, between 36 and 40°N, precipitation is concentrated in autumn and

winter (Pann<600 mm). Cool winters (minimal winter temperatures ranging between 5 and -

1°C) and hot, dry summers promote the development of Mediterranean forest. Modern sea

surface conditions along the western European margin between 37°N and 45°N are

characterized by mean annual temperatures ranging from 18°C to 14.5°C, respectively.

Table S1 – Stratigraphic events identified by 5-6 and dated after Svensson et al., 2008,

Shackleton et al., 2000 and 2003, Sanchez Goñi et al., 2012 used to: a) develop the linear

interpolation model of core MD95-2042, and b) the age models of the other western

Air–sea temperature decoupling in western Europe during the last interglacial–glacial transition

SUPPLEMENTARY INFORMATIONDOI: 10.1038/NGEO1924

NATURE GEOSCIENCE | www.nature.com/naturegeoscience 1

© 2013 Macmillan Publishers Limited. All rights reserved.

http://www.nature.com/doifinder/10.1038/ngeo1924

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European margin cores. These chronologies are based on the correlation of identified and

dated forest increases in MD95-2042 to the same identified forest increases in cores MD99-

2331 and MD04-2845.

a

Event stratigraphy Reference MD95-2042 References Age ka

Depth (cm)

D-O 12* Shackleton et al., 2004 1548 Svensson et al., 2008 46.86



MIS 5a lightest value Shackleton et al. 2003 2140 Shackleton et al., 2000, 2003 82.9

MIS 5e/5d Shackleton et al. 2003 2492 Sanchez Goñi et al., 2012 120

b Event stratigraphy MD95-2042 Age ka MD04-2845 MD99-2331

Depth (cm) Depth (cm) Depth (cm)

Forest increase (D-O 12) 1548 46.86 1335 1150



HS 6 (strong N. pachyderma (s) increase) 1845 64.6 1675 1435

Forest increase (Stadial II/Ognon II) 1975 72.57 1815 1525

Forest increase (Stadial I/Ognon I) 2035 76.33 1855 1565

Forest increase (Mélisey II/St Germain II) 2135 82.4 1910 1620

Forest decrease (St Germain 1c/Mélisey II) 2185 87.4 1930 1665

Figure S1 – Comparison of a) summer and winter foraminifera-based SST records and the

percentage curve of subtropical and temperate planktonic foraminifera with b) pollen

percentage records of different taxa from core MD04-2845 retrieved in the Bay of Biscay.

Grey bands indicate warm/temperate phases in western France. The clear identification of


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the Ognon II Interstadial after the abrupt increase of the Atlantic forest pollen percentages

demonstrates that this interstadial is a real climate event and not the result of pollen

reworking as previously suggested 7. HS 6 indicate Heinrich Stadial 6. Grey bands indicate

warm phases.


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Figure S2 – Constrained Correspondence Analysis (CCA) showing the sample scores on the

ordination space for the pollen record of core MD04-2845 and using foraminifera-based

summer (jas) SST as constraining variable. The CCA between the five main pollen ecological

groups, Atlantic forest, Picea, Abies, Ericaceae (heathlands), grasslands and semi-desert, and,

using summer SST as constraining variables statistically confirmed our observations.

Numbers refer to sample ages in thousands of years (ka).


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Figure S3 – a) Temperature record of Greenland 8-10 compared with the western European

margin palaeoclimatic records for the interval 85-50 ka: b) M04-2845 (Bay of Biscay): Atlantic

forest pollen percentages, foraminifera-based SST, benthic foraminifera δ18O and IRD

concentrations (grey surface), c) MD99-2331 (northwestern Iberian margin): Atlantic forest

and Ericaceae (heathlands) pollen percentages, foraminifera- and Uk’37-based SST, benthic

foraminifera δ18O, IRD concentrations (grey surface) and N. pachyderma (s) percentages

(black line). Note the tight correlation between the Ericaceae and the foraminifera-based

SST records that show heathland expansion at the expense of the Atlantic forest contraction

when SST are relatively warm, higher than 9°C in summer, and e) MD95-2042 (southwestern

Iberian margin): pollen percentages, Uk’37-based SST, benthic foraminifera δ18O, IRD

concentrations (grey surface) and N. pachyderma (s) percentages (black line). The onset of

HS (Heinrich Stadial) 6 in the south westernmost site is marked by the strong increase in N.

pachyderma (s). C19 is marked by the slight occurrence of IRD in the northern cores. MIS

refers to Marine Isotopic Stages.


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Figure S4 – Comparison between summer SST reconstruction curves for core MD04-2845. This figure

shows no substantial differences between the two curves apart from a tendency of SIMMAX (green

line) to smooth SST between 80 and 73 ka. The SIMMAX SST estimates fully confirm persistent warm

conditions in the Bay of Biscay during the MIS5e/4 transition. We have used MAT (black line) instead

of SIMMAX because it has been shown that the former accurately reconstruct SST 11.


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References

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3 Frouin, R., Fiúza, A. F. G., Ambar, I. & Boyd, T. J. Observations of a poleward surface current off the coasts of Portugal and Spain during winter. Journal of Geophysical Research 95, 679-691 (1990).

4 Ozenda, P. Les végétaux dans la biosphère. (Doin, 1982).

5 Shackleton, N. J., Sanchez Goñi, M. F., Pailler, D. & Lancelot, Y. Marine Isotope Substage 5e and the Eemian Interglacial. Global and Planetary Change 757, 1-5 (2003).

6 Shackleton, N. J., Fairbanks, R. G., Chiu, T. & Parrenin, F. Absolute calibration of the Greenland time scale: implications for Antarctic time scales and for Δ14C. Quaternary Science

Reviews 23, 1513-1523 (2004).

7 Keigwin, L. D., Curry, W. B., Lehman, S. J. & Johnsen, S. The role of the deep ocean in North Atlantic climate change between 70 and 130 kyr ago. Nature 371, 323-326 (1994).

8 Huber, C. et al. Isotope calibrated Greenland temperature record over Marine Isotope Stage 3 and its relation to CH4. Earth and Planetary Science Letters 243, 504-519 (2006).

9 Landais, A. et al. A continuous record of temperature evolution over a whole sequence of Dansgaard-Oeschger during Marine Isotopic Stage 4 (76 to 62 kyr BP). Geophysical Research

Letters 31 (L22211), 101-113, doi:doi: 10.1029/2004GL021193 (2004).

10 Capron, E. et al. Millennial and sub-millennial scale climatic variations recorded in polar ice cores over the last glacial period. The Climate of the Past 6, 345-365 (2010).

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