Transcript SYNTRACE2010 - International Pacific Research Center

Transient Paleoclimate Simulations
with LOVECLIM
Oliver Elison Timm,
International Pacific Research Center,
University of Hawai`i at Mānoa
Laurie Menviel,
now at Climate and Environmental Physics,
University of Bern
Tobias Friedrich,
International Pacific Research Center,
University of Hawai`i at Mānoa
Ayako Abe-Ouchi,
CCSR, University of Tokyo
and JAMSTEC, Yokohama
Fuyuki Saito,
JAMSTEC, Yokohama
Axel Timmermann,
International Pacific Research Center,
University of Hawai`i at Mānoa
Presented at the Synthesis of Transient Climate Evolution of the last 21-kyr
(SynTraCE-21) PAGES Working Group Meeting,
Timberline Lodge on Mt. Hood, Oregon, October 10-13, 2010
Pioneers in the field of transient paleoclimate
modeling with EMICs and GCMs:
Hubert Gallee, J.P. van Persele, Th. Fichefet, Ch. Tricot, and A. Berger,
Simulation of the Last Glacial Cycle by a Coupled, sectorially averaged
climate-ice sheet model
, JGR, 1992
John Kutzbach and P.J. Guetter: The influence of changing orbital
parameters and surface boundary conditions on climate simulations for the
past 18,000 years. J. Atmos. Sci., 1986.
These image may be subject to copyright
Transient Paleoclimate Simulations
with EMICs
(Earth System Model of Intermediate Complexity)
o Holocene
Climate (Examples)
o only one major forcing factor: orbital changes
o Claussen et al. GRL 1999: Simulation of an abrupt change in Saharan
Vegetation in the mid-Holocene.
o Crucifix et al. Clim. Dyn., 2002: Climate Evolution during the Holocene:
A study with and earth system model of intermediate complexity
o Renssen et al., Clim. Past, 2007: On the importance of initial
conditions for simulations of the mid-Holocene climate
Transient Paleoclimate Simulations
with EMICs
o Last
deglaciation
o Charbit et al., Glob. Planet. Change, 2005: Investigating the
mechanisms leading to the deglacitiation of past continental
Northern Hemisphere ice sheets with the CLIMBER-GREMLINS
model
o Lunt et al., Clim. Past, 2006: Comparing transient, accelerated
and equilibrium simulations of the last 30000 years with the
GENIE-1 model.
o Timm and Timmermann, J. Clim., 2007: Simulation of the last
21000 years using accelerated transient boundary conditions.
o Timm et al., Paleoceanography, 2008: On the definition on Paleoseasons in transient climate simulations
Overview:
We use LOVECLIM in transient
paleoclimate simulations to :
Elucidate the mechanisms of orbitally
forced Southern Hemispheric climate
change during the last 130,000 years.
Study the ‘anatomy’ of the last glacial
termination inclusive Heinrich 1, Antarctic
Cold Reversal, Younger Dryas
LOVECLIM
Transient
external forcing
Ice-sheet forcing
from ICIES
(GLIMMER)
In progress
ECBilt – atmosphere
T21, L3
Albedo +
orography
a
Air-sea
i fluxes
a
CLIO –
ocean sea-ice
3x3, L20
These image may be subject to copyright
VECODE –
vegetation
a
CO2 fluxes
i
a
LOCH –
Marine carbon cycle
Antarctic Temperature evolution, last 130 ka
Simulation
agrees well with
ice-core
reconstructions
Timing of the
deglaciation
correct even
without
Heinrich event 1
Timmermann, 2010, unpublished
Southern Hemisphere polar warming driven
by austral spring insolation and sea-ice feedback
Orbitally driven net shortwave irradiance changes at surface 80S-50S
Net downward SW flux anomaly due to
Orbital forcing only
Net downward SW flux due to sea-ice
related albedo changes
dQ
Q
A
Q
A
dA
Southern Hemisphere polar warming driven
by austral spring insolation and sea-ice feedback
Orbitally driven net shortwave irradiance changes at surface 80S-50S
Net downward SW flux anomaly due to
Orbital forcing only
Net downward SW flux due to sea-ice
related albedo changes
Timmermann et al., 2009
Southern Hemisphere polar warming driven
by austral spring insolation and sea-ice feedback
Orbitally driven net shortwave irradiance changes at surface 80S-50S
Combined effect on net downward SW flux
Timmermann et al., 2009
Southern Hemisphere polar warming driven
by austral spring insolation and sea-ice feedback
Timmermann et al., 2009
Observational evidence for strong austral spring
forcing of Southern Ocean climate change
Timmermann et al., 2010, in preparation
Quantifying the role of external forcings in driving
seasonal and annual mean deglacial climate change
Antarctica
Greenland
Timmermann et al., 2009
Summary 1
 Numerical simulation of of the last deglaciation
show that polar SH warming and sea-ice retreat
started around 18ka BP, consistent with paleoevidence.
 No freshwater forcing was used in our simulation
=> AMOC shutdown and seesaw effect not the sole
cause of SH warming.
 Our conjecture: local insolation “jump-started” the
deglaciation in the SH.
Disentangling the effects of orbital forcing on
climate and carbon cycle
Orbital forcing F
Complex spatiotemporal
signature
G(F)
Climate Response R:
Seasonal sensitivities
(Sea ice, westerlies,
MLD)
D(R)
Carbon cycle
Response C
Proxy Response D:
Seasonal sensitivities
(accum. etc)
Proposed mechanisms: Orbital forcing - Climate
Kawamura et al. 2007
Denton et al., 2010
Stott et al. 2007
Huybers and Denton 2008
Timmermann et al. 2009
What is the role of precession and obliquity forcing on winds,
sea-ice and temperatures in the Southern Hemisphere?
Optimal orbital forcing to change the winds?
Obliquity forcing
modulates
meridional
temperature
gradient
sea ice albedo
feedback leads to
further
amplification
From
From Loutre
Loutre et
et al.
al.,(2004)
2004
Obliquity effects on climate
LOVECLIM
Temperature response:
high-low obliquity
High obliquity: weaker winds
Low obliquity: stronger winds
Surface wind response:
high-low obliquity
Obliquity effects on SH climate
TEMPERATURE SUBTROPICS
MINUS ANTARCTICA
LOVECLIM,
DEUTERIUM EXCESS (Vimeux)
LOVECLIM SIMULATED
SH WESTERLIES STRENGTH
PRECIPITATION 30S-90S
LOVECLIM SIMULATED
“WIND x PRECIPITATION”
DUST FLUX EPICA
Timmermann et al., 2010, in preparation
Summary 2
 Obliquity forcing dominates the annual mean
meridional temperature gradient in the SH:
 Low obliquity increases the temperature gradient
and the strength of the westerly winds
 Last obliquity minimum (westerly winds maximum)
was 27,000 years ago
However, CO2 did not rise until 18,000 BP. Why ?
LOVECLIM
Transient
external forcing
Ice-sheet forcing
from ICIES
(GLIMMER)
In progress
ECBilt – atmosphere
T21, L3
Albedo +
orography
a
Air-sea
i fluxes
a
Freshwater
Forcing
CLIO –
ocean sea-ice
3x3, L20
This image may be subject to copyright
VECODE –
vegetation
a
CO2 fluxes
i
a
LOCH –
Marine carbon cycle
Last Glacial Termination
with freshwater forcing
YD
Menviel, et al., Quaternary Science Reviews, accepted, 2011
OCE326-GGC5
OCE326-GGC5
RC11-83
RC11-83
Menviel, et al., Quaternary Science Reviews, accepted, 2011
ODP 1002
MD03-2707
Menviel, et al., Quaternary Science Reviews, accepted, 2011
Hulu Cave
905
Menviel, et al., Quaternary Science Reviews, accepted, 2011
ODP1233
H214
MD97-2120
EPICA C
Vostok
RC11-83
TN057-21
TN057-13PC
Menviel, et al., Quaternary Science Reviews, accepted, 2011
Alkenone
content
MD97-2120
opal flux
TN057-13PC
Menviel, et al., Quaternary Science Reviews, accepted, 2011
Summary:
Proxy-observed orbital and millennial-scale climate
change signals can be reproduced with LOVECLIM
by prescribing orbital forcing , ice-sheets, GHG and
freshwater input
EMIC-type simulations: valuable tools for testing the
individual forcing factors, and feedbacks.
Last Glacial Termination: Southern AtmosphereOcean system warmed in response to orbital forcing
and sea-ice albedo feedback.
Obliquity-cycles change the meridional temperature
gradient and the strength of the SH westerly winds.
Accordingly, atmospheric CO2 should have increased
26ka BP, but the observed increase lacks the forcing.