Eastern Mediterranean sea surface temperatures and δ18O (in the SEEQS... · PDF...

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Transcript of Eastern Mediterranean sea surface temperatures and δ18O (in the SEEQS... · PDF...

  • Eastern Mediterranean sea surface temperatures and δ18O (in the late Quaternary)

    Kay-Christian Emeis1, Uwe Mikolajewicz2

    1IfBM, University of Hamburg, Bundesstr. 55, 210146 Hamburg, FRG

    2MPI for Meteorology, Bundesstr. 53, 20146 Hamburg, FRG

  • The modern Mediterranean Sea

    anti-estuarine circulation (E>>P), nutrient poor, little biological productivity. Climate setting/hydrology influenced by southern hemisphere/tropical and subtropical/monsoonal processes, and North Atlantic.

    87SL

    71SL 67SL78SL

    KL71

    KS8230

    RL11

    ODP 967

  • I. Sapropel periods and conditions

    Climate-driven changes in biogeochemical character of and material fluxes in a now extremely oligotrophic ocean.

    •Paced by insolation since the (Miocene)/Pliocene

    •Caused by anoxic conditions in deep water

    •Lasting several 1000 years

  • Lourens et al., 1998

    The astronomical pacemaker

    Sakamoto et al., 1998

  • Insolation/climate forcing

    Sapropels occur when northern hemisphere summer insolation is high and contrasts between seasons are large.

    In the late Quaternary they mark the transition glacial to interglacial conditions

    Age (k.y.before present)

    Ins ola

    tio n a

    t 6 5°

    N in

    su mm

    er (W

    /m 2 )

    400

    440

    480

    520

    2000 2400 2800 3200 3600 4000

    400

    440

    480

    520

    0 400 800 1200 1600 2000

    Onset NH glaciation

    Strong ice-volume effect

    Precession dominant

    Obliquity pronounced

  • freshwater input (+warming)

    Biology C:N:P,

    Export PP

    Chemistry Redox,C:N:P

    C-flux to Sediments

    Stratification

    The schematic chain of events

  • The schematic chain of events

    freshwater input (+warming)

    Biology C:N:P,

    Export PP

    Chemistry Redox,C:N:P

    C-flux to Sediments

    Stratification

    Climatic trigger: Low/high latitude?

    Biogeochemical consequences: Which processes are responsible for anoxia and increased C-burial?

  • Variations of δ18O in surface waters

    -3

    -2

    -1

    0

    1

    2

    3

    4 0 500 1000 1500 2000

    Age (k.y.)

    δ1 8 O

    pl an

    kto nic

    fo ra

    mi nif

    er s

    Equatorial Pacific (Site 677; N. Shackleton)

    Ionian Sea (KC01; M. Paterne) Levantine Sea (Site 967; D. Kroon)

    Exaggerated basin effect: Combination of freshwater input, warming of surface layer, enhanced stratification, and pooling at surface

  • The late Quaternary

  • Mediterranean sea surface temperatures

    0.4

    0.5

    0.6

    0.7

    0.8

    0.9

    0 1 2 3 4 5 6 7 depth in core M40/4-71

    U k´

    37 v

    al ue

    26

    23

    20

    17

    14

    11

    SS T

    (° C

    )

    S9S8S7S5S4S3S1 S6

    ∆SST=12°C

  • δ18O patterns in sapropels: late Quaternary

    -3

    -2

    -1

    0

    1

    2

    3

    0 1 2 3 4 5 6 7 depth in core M40/4-71

    18

    O G

    . r ub

    er δδ δδ

    ∆δ18O=4.3‰

  • δ18O seawater reconstruction

    Global ice effect = -0.12‰, Salinity = -3.4 psu

    ² 18 O= 1.9‰ δ

    -2.0

    -1.0

    0.0

    1.0

    16

    17

    18

    19

    20

    21

    22

    23

    24

    117 120 123 126 129

    δ 18

    O G

    . r ub

    er

    S S

    T (°

    C )

    age (kyr)

    Sapropel S-5/Levantine Basin

    ²SST=1.8°C= 0.36‰

    7°C = -1.47‰ 18 Oδ

  • ∆δ18Oseawater and ∆ SST associated with transition to sapropels/E.Med.

    2.0-0.6S10 5.1 2.2 3.5 -2.1 6.7 2.9 0.7 6.6

    -0.6S9 -0.5S8 -2.2S7 -4.7S6 -2.2S5 -2.6S4 -2.7S3 -2.3S1

    12

    14

    16

    18

    20

    22

    24

    -30-20-100102030

    SS T

    (° C

    )

    cm from sapropel base

    M40-71

    base S5

    -2

    -1

    0

    1

    2

    3

    18 O

    G . r

    ub er

    δ

    967

    969

    δ

  • Variations in SST of surface waters: Pliocene

    12 14 16 18 20 22 24 26

    420

    440

    460

    480

    500

    520

    540

    2220 2230 2240 2250 2260

    S S

    T( °C

    ) Insolation

    Age (k.y.)

    3 k.y.

    Insolation cycle 218Insolation cycle 216

    Base of Sapropel Base of Sapropel

  • Variations in δ18O of foram calcite: Pliocene

    -1

    0

    1

    2

    400

    420

    440

    460

    480

    500

    520

    540

    2220 2230 2240 2250 2260

    S um

    m er insolation 65°N

    (W /m

    2)

    Insolation cycle 218Insolation cycle 216

    Base of sapropelBase of sapropel

    Age (k.y.)

    δ1 8 O

    pl an

    kto nic

    fo ra

    mi nif

    er s

  • Not so much the absolute temperature…. A

    ve ra

    ge S

    S T

    in s

    ap ro

    pe ls

    (° C

    )

    δ1 8 O

    be nth

    ic for

    am ini

    fer sim

    Ea ste

    rn

    Eq ua

    tor ial

    Pa cif

    ic (S

    ite 84

    6, Mi

    x e t a

    l., 19

    95 )

    12

    14

    16

    18

    20

    22

    24

    26 2.5

    3

    3.5

    4

    4.5

    5

    0 500 1000 1500 2000 2500 3000 3500

    Age (k.y.)

  • -3

    -2

    -1

    0

    1

    2

    3

    4

    -3

    -2

    -1

    0

    1

    2

    3

    0 500 1000 1500 2000 2500 3000 3500

    …nor an absolute value of seawater δ18O… Av

    er ag

    eδ 18

    O s ea

    wa ter

    in sa

    pr op

    els

    Age (k.y.)

    δ1 8 O

    be nth

    ic for

    am ini

    fer sim

    Ea ste

    rn

    Eq ua

    tor ial

    Pa cif

    ic (S

    ite 84

    6, Mi

    x e t a

    l., 19

    95 )

    …but the change from cold&dry to warm&wet

  • Stratification, anoxia and enhanced C- flux...........

    Fresh water influx and warming of surface waters enhance stratification.

    Winter convection ceases to supply deep water, anoxia results.

    Production increases due to changed internal cycling of phosphorus.

    -2-10123

    2.5

    3

    3.5

    4

    4.5

    18O G. ruberδ

    10 15 20 25

    SST (°C)

    0 50 100150 200 250

    primary production (g C m-2 yr-1)

    from Ba bio

    >10°C>4 permil

    S6

    S5

    S7

    S4

    E m

    ei s

    et a

    l., 2

    00 3,

    W el

    de ab

    et a

    l., 2

    00 3

    Monsun- signal

    ∆S= -9 psu

    Time: 200 – 100 ka

  • S6

    S5

    Meteor 40-4, 71SL, 220-480 cm

    S7

    0 200 400 600

    2.5

    3

    3.5

    4

    4.5

    C:P molar ratio

    -2 0 2 4 6 8 15N/14N

    0 50 100150200250

    primary production (g C m-2 yr-1) from Babio flux rates

    ......from natural eutrophication

    Phosphorus is lost from sediments.

    Winter convection entrains P-rich waters into surface.

    N:P ratios favor N- fixation.

  • Classical moisture sources

    Ryan, 1972 (and many others later) Picture from Mangerud et al.,2001

    Rossignol-Strick, 1983 Picture from Ruddiman, 2001

    Northern hemisphere Southern hemisphere/tropical processes

  • Less classical moisture sources

    Béthoux and Pierre, 1999 Rohling et al., 2004

    ∆ North Atlantic/Mediterranean ITCZ relocation sea water density differences

    Gibraltar

  • Argentarola cave

    Soreq/ Pequiin caves

    Core M40-71SL

    Linking terrestrial and marine records

  • -2

    0

    2

    4

    δ1 8 O

    G . r

    ub er

    4 cores eastern Mediterranean

    δ 18O

    10

    15

    20

    25

    S S

    T (°C )

    SST

    2 cores eastern Mediterranean

    -8

    -6

    -4

    -2

    0 50 100 150 200 250

    S1 S3 S4 S5 S6 S7 S8 S9

    δ1 8 O

    s pe

    le ot

    he m

    c al

    ci te

    age (kyr)

    Pequin+Soreq caves

    δ 18O

    δ18O in speleothems and marine forams (Bar-Matthews et al., 2003; Emeis et al., 2003)

  • -2

    0

    2

    4

    δ1 8 O

    G . r

    ub er

    4 cores eastern Mediterranean

    δ 18O

    10

    15

    20

    25

    S S

    T (°C )

    SST

    2 cores eastern Mediterranean

    -8

    -6

    -4

    -2

    0 50 100 150 200 250

    S1 S3 S4 S5 S6 S7 S8 S9

    δ1 8 O

    s pe

    le ot

    he m

    c al

    ci te

    age (kyr)