Global warming and abrupt ocean circulation changes at the Paleocene/Eocene boundary (55 Ma)

Malte HeinemannMentor: Jochem Marotzke

motivation

PETM: Paleocene/Eocene Thermal Maximum (55 Ma b.p.)

hypothesis: ocean circulation switch caused methane hydrate release

global warming due to GHG increase - source unclear

tool: AO-GCM with P/E boundary conditions

-6000 0 30003000[m]

MPI-OM ECHAM5

OASIS

motivation

results I:temperature

results II:ocean

circulation

summary& outlook

P/E control simulation

GHG concentrations poorly constrained by dataCO2=560ppm, preindustrial CH4 already yields warm climate:

0 6[oC]

241812 3630

surface temperature:

motivation

results I:temperature

results II:ocean

circulation

summary& outlook

P/E control simulation

reconstruction(Nunes & Norris 2006):

Atlantic deepwater track fits with that inferred from δ13C for the PETM, but not the pre-PETM:

our simulation(690m-2650m):

motivation

results I:temperature

results II:ocean

circulation

summary& outlook

PETM

pre-PETM

summary & outlook

even using a moderate GHG forcing, the simulated P/E climate is very warm (mostly due to a low surface albedo);Atlantic deepwater formation occurs in the proto-Labrador Sea;

next step: investigate climate and ocean circulation sensitivity to greenhouse gas forcing.

we performed a coupled atmosphere-ocean GCM simulation with Paleocene/Eocene boundary conditions;

motivation

results I:temperature

results II:ocean

circulation

summary& outlook

THANK YOU!

motivation

results I:temperature

results II:ocean

circulation

summary& outlook

spares

65 million years of climate change: global deep-sea oxygen isotope ratio based on more than 40 DSDP and ODP sites; modified from Zachos et al. (2001);

tem

pera

ture

[o C

](fo

r an

ice-fr

ee o

cean

)

bent

hic

δ18 O

[‰

]

Million years ago

1210864

0 10 20 30 40 50 60

0

3

2

1

4

5

motivation

results I:temperature

results II:ocean

circulation

summary& outlook

spares

7

[oC]

8

9

100 200

0100

0500 150

0

6

[oC]

9

15

180 200

0100

0500 150

0

3

12

dept

h [k

m] 1

2345

6

[oC]

9

15

18

time [years]0 200

0100

0500 150

0

3

12

dept

h [k

m] 1

2345

6

[oC]

9

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time [years]0 200

0100

0500 150

0

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12

12345

12345

Arctic Ocean ‘Wedell’ Sea

Pacific Atlantic

motivation

results I:temperature

results II:ocean

circulation

summary& outlook

spares

0 600300 900 15001200[m]

convective depth:

motivation

results I:temperature

results II:ocean

circulation

summary& outlook

spares

P/E

preind.

motivation

results I:temperature

results II:ocean

circulation

summary& outlook

spares

020004000

bathymetry [m]

upper 690m:

motivation

results I:temperature

results II:ocean

circulation

summary& outlook

spares

690m-2650m:

bathymetry [m]0200040006000

P/E control simulation

GHG concentrations poorly constrained by dataCO2=560ppm, preindustrial CH4 already yields warm climate:

0 6[oC]

241812 3630 latitude [deg. North]-90 0 9060303060

010

403020

[oC]

-10

surface temperature: zonal meanland surface temperature:

motivation

results I:temperature

results II:ocean

circulation

summary& outlook