Surface ocean warming and hydrographic change in the North Atlantic during the Middle Eocene Climatic Optimum

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Surface ocean warming and hydrographic change in the North Atlantic during the Middle Eocene Climatic Optimum

R.vanderPloeg@uu.nl @Robin_vd_Ploeg

1) Department of Earth Sciences, Utrecht University, Utrecht, the Netherlands

2) Bjerknes Centre for Climate Research and Department of Earth Science, University of Bergen, Bergen, Norway

3) Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, United Kingdom 4) NIOZ Royal Netherlands Institute for Sea Research and Utrecht University, Den Burg, Texel, The Netherlands

3) School of Environment, Earth & Ecosystem Sciences, The Open University, Milton Keynes, United Kingdom

Robin van der Ploeg ¹ , Margot J. Cramwinckel ¹ , Thomas J. Leutert ² , Steven M. Bohaty ³ , Chris D. Fokkema ¹ ,

Rogier J. Hidding ¹ , Ilja J. Kocken ¹ , A. Nele Meckler ² , Anne E. van der Meer ¹ , Jack J. Middelburg ¹ , Inigo A. Müller ¹ , Francien Peterse ¹ , Gert-Jan Reichart ^1,4 , Stefan Schouten ^1,4 , Philip F. Sexton ⁵ ,

Paul A. Wilson ³ , Martin Ziegler ¹ , Appy Sluijs ¹

How global was MECO warming?

IODP Sites U1408 and U1410 (Newfoundland Drifts):

- highest resolution MECO interval recovered so far

- multiproxy temperature reconstructions possible due to well-preserved foraminifera and abundant organic matter

A new U1408/U1410 MECO composite record

- Revised stratigraphic correlations for MECO interval based on XRF data - MECO peak warmth interval likely missing at U1408 but present at U1410

High-resolution clumped isotope paleothermometry and multiproxy temperature reconstructions

- Surface mixed-layer warming of 4 ˚C during MECO inferred from Δ ₄₇ measurements on two species of planktonic foraminifera

- Combined foraminiferal Δ ₄₇ and δ ¹⁸ O data yield seawater δ ¹⁸ O increase of ~0.5 ‰, may indicate transient salinization of North Atlantic

- Multiproxy comparison between Δ ₄₇ , Mg/Ca and TEX ₈₆ results in roughly similar estimates of warming (2 - 4 ˚C), but absolute values differ greatly and depend on calibration used

Overview of sites with existing MECO records, with degree of MECO warming inferred shown in boxes (°C of warming).

50 60 70 80 90 100

0.0 −0.5

−1.0

−1.5

−2.5

−2.0

δ

18

O ( ‰ )

U1408 U1410

Bulk carbonate

Depth (m, CCSF−X Bohaty)

50 60 70 80 90 100

C18n.1n ^C18n.1r

C18n.2n C18r

50 60 70 80 90 100

0 50 100 150

Ca/ Fe (offset)

U1408 (+0) U1408A (+20) U1408B (+40) U1408C (+60)

U1410B (+80) U1410C (+100)

U1410 (+0) Ca/Fe data from Boulila et al. (2018)

Polarity Chrons

50 60 70 80 90 100

1.0 2.0 3.0 4.0 5.0

δ

13

C ( ‰ )

A. (prae-)topilensis

Gk. index

Bulk carbonate

50 60 70 80 90 100

0.0 −1.0

−1.5

−0.5

−2.0

−2.5

δ

18

O ( ‰ )

A. (prae-)topilensis

Gk. index Bulk carbonate

Depth (m, CCSF−X Bohaty)

50 60 70 80 90 100

C18n.1n ^C18n.1r

C18n.2n C18r

50 60 70 80 90 100

15 20 25 30 35

Δ

47

-based t empe rature ( ºC)

A. (prae-)topilensis

Gk. index

Kele et al. (2015) calibration with Brand et al. (2010) parameters

2SEMean MC simulations

+ LOESS fits Median

68% CI 95% CI

Clusters

50 60 70 80 90 100

−0.5 0.5 0.0 1.0 1.5 2.0

Seawater δ

18

O ( ‰ )

Derived using Kim & O’Neil (1997) calibration for synthetic calcite and median values from Δ₄₇-derived temperatures

Polarity Chrons

50 60 70 80 90 100

15 20 25 30 35

Δ

47

-based t empe rature ( ºC)

A. (prae-)topilensis

Gk. index

2SEMean MC simulations

+ LOESS fits Median

68% CI 95% CI

Clusters

Kele et al. (2015) calibration with Brand et al. (2010) parameters

50 60 70 80 90 100

16 18 20 22 24 26 28

Mg/Ca -based t empe rature ( ºC)

MC simulations

+ LOESS fits Median

68% CI 95% CI

A. (prae-)topilensis

Gk. index

Gray et al. (2018) calibration modified after Evans & Müller (2012) Assumptions: pH = 7.6 - 8.0 (7.8), Mg/Ca_sw = 1.5 - 3.0 (2.25), S = 32 - 36 (34)

50 60 70 80 90 100

27 28 29 30 31 32

TEX

86

-based t empe rature ( ºC)

U

^K’₃₇

at saturation TEX

₈₆^H

Kim et al. (2010) calibration

(But very high BIT values throughout) LOESS fit

Median

68% CI 95% CI

Depth (m, CCSF−X Bohaty)

50 60 70 80 90 100

C18n.1n ^C18n.1r

C18n.2n C18r

Polarity Chrons

50 60 70 80 90 100

−4

−2 0 2 4 6

Tempe rature anomaly ( ºC)

Mg/Ca A. (prae-)topilensis

TEX₈₆^H

Δ₄₇ A. (prae-)topilensis Individual

datapoints

Individual datapoints

Surface ocean warming and hydrographic change in the North Atlantic during the Middle Eocene Climatic Optimum