Sensitivity of the Western Mediterranean Sea to Holocene

climate variability

Isabel Cacho1, Gemma Herrera1, Jaume Frigola1, Miquel Canals1 & Ana Moreno2

1 GRC Geociències Marines,Universitat de Barcelona2 Instituto Pirenaico de Ecología – CSIC - Zaragoza

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OutlineC

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1. Sensitivity of the W Mediterranean surface and deep waters to past rapid climate variability

2. Climate instability/stability along the Holocene

3. Response of the W Mediterranean to Holocene millennial-centennial climate variability

4. Summary and future lines

2/16

Past climate variability in Greenland

GISP2

Dansgaard-Oeschger

Cycles

Holocene

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Warm

Cold

Age (ka BP)

Dansgaard et al. (1993)

Greenland-Mediterranean connectionsC

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0 5 10 15 20 25 30 35 40 45 50

Age (cal. kyr B.P.)

D-O variability in Mediterranean SST

H1 H2 H3 H4 H5YD

0

2

4

6

8

10

(%)

Cacho et al. 1999 (Paleoceanography)

GISP2Greenland

GISP2 Dome (Greenland)

Emiliania huxleyi

MD95-2043Alboran Sea

0 5 10 15 20 25 30 35 40 45 50

Age (cal. kyr B.P.)

8

10

12

14

16

18

20

AlkenoneSST (°C)

-44

-42

-40

-38

-36

-34

-32

ice18O (‰)

N. pachyderma (s)

N. pachyderma (s)

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D-O variability in WMDW?

39.0

>39.0

>39.039.0

17.018.2

15

20

38.75

38.65

38.65

>20.0

20o 25o 30o 35o E

CR

ET

A S

ILL

RH

OD

OS

SIL

L

LIW

EMDW

>38.0

37.5

38.0

38.5

38.0

38.0

38.5

38.75

38.65SIC

ILIA

SIL

L

10o 15o

37.0

MA

LT

A S

ILL LIW

EMDW

37.5

>38.0

36.0

35.5

35.535.0 35.0

36.0

35.5

36.0

38.4

38.4

38.5?

36.5

38.4

10o W 5o 0o 5o E

GIB

RA

LT

AR

SIL

L

AL

BO

RA

N S

ILL

4,000

3,000

2,000

1,000

0

Depth(m) 37.0

MAW

LIW

WMDW

MOW

35°

45°

40°

MarAdriático

MarEgeo

MarNegro

MarJónicoMar de Alborán

Golfo deCádiz

MarTirrreno

Estrechode Sicilia

Estrecho deGibraltar

-10 ° -5 ° -0 ° 5 ° 10 ° 15 ° 20 ° 25 ° 35 °30 °

CuencaLevatina

Golfo deLeón

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D-O variability in WMDW

H2H1 H3 H5H4YD

-44-42-40-38-36-34-32

GISP218O (‰)

4.8

4.4

4

3.6

3.2

2.8

18O (‰)

2

1.6

1.2

0.8

0.4

13C (‰)

-4

0

4

8

12

0 5 10 15 20 25 30 35 40 45 50

Age cal. Kyr B.P.

Po

lar

Circ

ula

tion

In

de

xG

ISP

2

Cacho et al., 2001 (Earth Planet. Sc. L.); Cacho et al., 2006 (QSR)

Colder/saltierWMDW

More oxygenatedWMDW

More intense atmospheric circulation

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Modes ofWMDW

variability

Interstadial Mode:Pour ventilated WMDW

Stadial Mode:Well ventilated WMDW

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Colder/saltierWMDW

More oxygenatedWMDW

MD95-2043 (dark) and MD99-2343 (light)

H2H1 H3 H5H4YD

10 20 30 40 50

21.6

1.2

0.8

0.44.84.44

3.63.22.8

13C

(‰

)18

O (

‰)

Cacho et al., 2001 (EPSL) and 2006 (QSR)Sierro et al., 2005 (Paleoc.)

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Holocene Atmospheric VariabilityC

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Mayewski et al. 2004 (Quat. Res.)

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Holocene variability in North Atlantic Ocean

• Holocene ice rafted events: fresh volcanic glass and hematite-stained grains

Bond et al., (1997)

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Viking expansion during the MWPC

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C37

Alk

enon

es(n

g/g)

Alk

enon

eSS

T (º

C)

18O(‰)

Age (cal. Ky BP)

GISP2 - Greenland

MD 95-2043 - Alboran

8.2 event

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

0

400

800

1200

1600

2000

10

12

14

16

18

20

-42

-40

-38

-36

-34

-32

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Cacho et al., 2002 (JMS)Rogerson et al 2008 (G3)

Last ORL

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Holocene Variability in the Mediterranean (I)12/16

GISP2

UP1

0 (%

)

Si/A

l

18O (‰)G. bulloides

SST

(ºC

)

18O

(‰)

ice 18O (‰)

ice

Age (ka BP)

Alboran Sea

Menorca Rise

Alboran SST

Frigola et al., 2007 (Paleoceanography) & 2008 (Quarter. Inter.)

0 4 8 12

3

2

1

0

20

30

40

50

60

70

2.6

2.7

2.8

2.9

3

3.1

-42

-40

-38

-36

-34

-32

-35.2

-34.8

-34.4

-34

14

16

18

20

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Fastest Deep water current

Stronger WMDW overturning

Holocene Variability in the Mediterranean (II)13/16

Age (ka BP)

Menorca SST

0 4 8 12

20

30

40

50

60

70

2.6

2.7

2.8

2.9

3

3.1

16

18

20

22

??

UP1

0 (%

)

Si/A

lSS

T (º

C)

Frigola et al., 2007 (Paleoceanography); Herrera unpublished

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Holocene Variability in the Mediterranean (III)

Fastest Deep water current

Stronger WMDW overturning

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Potential causes of Holocene Variability in the Mediterranean

Could a persistent/intense +NAO state cause Holocene events of enhance WMDW overturning?

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1. Mediterranean Sea has been very sensitive to past rapid climate variability, inducing changes in both surface and deep water masses

2. Western Mediterranean Deep Water cell was very sensitive to Holocene climate variability:

- Recurrent events of faster deep water currents- Parallel cooling of surface layer (1.5-3ºC)

Summary

Future Lines1. Precise characterization of the Holocene variability: reproducing present records at different sites and with different proxies and with improved timing constrain.

2. Reconstruct water properties at deep and also intermediate water layer.

Acknowledgments

• Consolider GRACCIE: Multidisciplinary Research Consortium on GRadual and Abrupt Climate Changes, and their Impacts on the Environment

• The Comer Science & Education Foundation (USA)

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extra

Announcement

Surface Ocean Lower Atmosphere Study