Hotspot of CO2 fluxes along the Polar Front
Link with the Southern Ocean circulation
Landshutzer et al., 2015
OCEAN & ATMOSPHERE – CLIMATE SCIENCE CENTER
Clothilde Langlais, Andrew Lenton, Paula Condepardo, Judith Hauck, JB Sallee,
Andreas Klocker, Joan Llort, Richard Matear, Steve Rintoul
What do we know about Carbon fluxes? What are the
limitations?
Lenton et al., 2013
Air-sea CO2 fluxes year 2000
44oS
outgazing
58oS
Southern Ocean is
responsible for a carbon
uptake of 0.27to 0.43
PgC/yr south of 44∘S ,
and ~1PgC/yr south of
30oS.
OBSERVATIONS
uptake
Limitations:
• Lack of observations
• Poor Understanding
of high latitude
carbon cycle
• Poor Understanding
ocean circulation
Overturning circulation and CO2 fluxes
Surfacing of CDW favours outgassing
Changes in the overturning
has been linked with
changes in strength of the
carbon sink
Deep-ocean:
main reservoir
of carbon
Rintoul, 2000
Interannual-decadal scale
[Lenton and Matear , 2007;
Lovenduski et al. , 2008]
[Landshutzer et al. 2015]
Glacial-interglacial scale
[Barker et al., 2009 ;
Anderson et al., 2009]
What do we know about CDW pathways?
The upward pathway and the underlying physical mechanisms remain poorly understood.
Outcropping of CDW : in-between South ACC front (sACCf) and ACC Southern Boundary (sBy)
[Orsi et al. 1995]
Transport and transformation
of CDW
Mid-depth : along-isopycnals
flow + wind-induced
divergence + air-sea fluxes
Deeper : diapycnal mixing
accounts for most of the
transport
[Marshall and Speer, 2012,
Nikurashin and Ferrari 2013 ]
1/10O Ocean Forecasting Australia Model (OFAM3) Zhang et al., 2016
• MOM4 ocean model
• 50 z-level
• WOMBAT BGC model
OBSERVATIONS 1993-2014
1/10o
• 20 yr Spin-up with 1979
• 1979-2014 historical run :
JRA-55 surface forcing (bulk formulae)
• State-independent restoring below 2000m
Air-sea CO2 fluxes
uptake
uptake
outgassing
Historical
OFAM3 JRA55
outgassing
Observations
Takahashi et al., 2009
nominal year 2000
CO2 outgassing, ACC jets and CDW outcrop
Lenton et al. 2013: 0.27to 0.43 PgC/yr
44oS
0.32
Pg/yr
44oS
0.33 Pg/yr
PF-south
58oS
-0.01 Pg/yr
Anomaly of ocean pCO2 along the PF-south
LONGITUDE
dx
dx
dx
dx
dx
Anomaly of ocean pCO2 along the PF-south
DIC
DIC-T
DIC
DIC-T
DIC-T
DIC-T
DIC+ALK
T
S
DIC
ALK
DIC+ALK
Supply of DIC in the mixed layer
Anomaly of ocean pCO2 along the PF-south
DIC in mixed layer
LONGITUDE
Less outgassing
section at 110E
September
Ekman
pumping
CO2 flux
sBy sACCf
PF
PF-south
natural
CDW
ASW
Stronger Outgassing
Section at 80E
September
Ekman
pumping
CO2 flux
sBy
PF
PF-south
sACCf
natural
CDW
ASW
Merging of
ACC jets at the
Fawn Trough
Take home message:
CDW surfacing is influenced by bathymetry
Surfacing of CDW favours outgassing
Changes in the overturning
has been linked with
changes in strength of the
carbon sink
Deep-ocean:
main reservoir
of carbon
Perspective:
Interannual variability
Seasonal cycle of CO2 fluxes
Rintoul, 2000
Interannual-decadal scale
[Lenton and Matear , 2007;
Lovenduski et al. , 2008]
[Landshutzer et al. 2015]
Glacial-interglacial scale
[Barker et al., 2009 ;
Anderson et al., 2009]
Which resolution for this problem?
Observations
1/10o
1/4o
1o
14 | Future of C in Southern Ocean| C. Langlais
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Fig. Supp 1 : Stationary Rossby waves: location and impact of resolution . a. AVISO 1993-2014 time-mean geostrophic
velocities and SSH contours and b. 1/10 ° model topography. Time-mean model horizontal velocities average over the top
200m and SSH contours (left), and time-mean model vertical velocities at 200m (right), for 3 different resolution: 1/10° (c.
and d.), 1/4 ° (e. and f.) and 1 ° (g. and h.). Black contours show SSH contours with SAF and PF in bold.
Anthropogenic Carbon (Cant ) in Southern Ocean
Southern Ocean contributes to
30% of sink of anthropogenic carbon
dioxide
Inventory of 25+/-5 Pg C
in Southern Hemisphere
Ito et al. 2010
17 | Future of C in Southern Ocean| C. Langlais
Takahashi et al., 2002
21 | Presentation title | Presenter name