The Southern Ocean in a high-CO2

Changes in inorganic and organic carbon fluxes

Judith Hauck, Christoph V ¨olker, Tingting Wang Mario Hoppema, Martin Losch, Dieter Wolf-Gladrow

Alfred Wegener Institute for Polar and Marine Research

. . . BACKGROUND

. . . THE MODEL

. . .

RESPONSE TOSAM

. . CONCLUSIONS

T ^HE S ^OUTHERN O ^CEAN

THE PREINDUSTRIAL CARBON CYCLE

T ^HE S ^OUTHERN O ^CEAN

THE PREINDUSTRIAL CARBON CYCLE

T ^HE S ^OUTHERN O ^CEAN

THE CONTEMPORARY CARBON CYCLE

S ^OUTHERN A ^NNULAR M ^ODE (SAM)

SAM Index:

Sea level pressure anomalies between the subpolar low and and the subtropical high-pressure systems

S ^OUTHERN A ^NNULAR M ^ODE (SAM)

SAM Index:

Sea level pressure anomalies between the subpolar low and and the subtropical high-pressure systems

S ^OUTHERN A ^NNULAR M ^ODE (SAM)

Polar Front

Antarctic shelf

surface ocean

deep ocean Increased

westerlies

Antarctica

atmosphere

S ^OUTHERN A ^NNULAR M ^ODE (SAM)

Polar Front

Antarctic shelf

surface ocean

deep ocean Increased

westerlies

Antarctica

atmosphere

Counter-acting transport by eddies?

E ^COSYSTEM M ^ODEL RE ^CO M-2

Chemistry C / ALK / N / Si / Fe

CO2 dust/Fe

Small Phytoplankton C / N / CaCO3 / Chl

Diatoms C / N / Si / Chl

Zooplankton C / N

Detritus C / N / Si / CaCO3

Dissolved Organic Material C / N

Geider et al., 1998; Schartau et al., 2007; Hohn et al., 2009; Hauck et al., GBC, under review

M ^{ODEL RUNS}

1900 1947 2010

A tm C O

Climatological forcing (CORE)

Climatological dust

Inter-annual varying forcing (NCEP-R1)

Monthly dust (1979-2010)

M ^{ODEL RUNS}

1900 1947 2010

A tm C O

Climatological forcing (CORE)

Climatological dust

Inter-annual varying forcing (NCEP-R1)

Monthly dust (1979-2010)

Only changes due to perturbed atmospheric forcing

Changes due to atm CO2 increase AND perturbed atmospheric forcing

M EAN MODEL STATE

MOST LIMITING FACTORS FOR PHYTOPLANKTON GROWTH

Feb Feb

Nanophytoplankton Diatoms

Si-limitation N-limitation

Fe-limitation

R ^{ESPONSE TO} SAM

Satellite-derived SST (°C) response

per unit increase SAM Index

-0.4 -0.2 0 0.2 0.4 ^{−0.5 −0.25 0 0.25 0.5}

Modelled SST (°C) response

per unit increase SAM Index

R ^{ESPONSE TO} SAM

−0.05 0 0.05 0.1 0.15

Modelled total chlorophyll response

(mg m^-3 per unit increase SAM)

R ^{ESPONSE TO} SAM

−0.05 0 0.05 0.1 0.15

Modelled total chlorophyll response

(mg m^-3 per unit increase SAM)

R ^{ESPONSE TO} SAM

−0.05 0 0.05 0.1 0.15

Modelled total chlorophyll response

(mg m^-3 per unit increase SAM)

C ARBON BUDGET

C ARBON BUDGET

C ARBON BUDGET

C ARBON BUDGET

C ARBON FLUX ANOMALIES AT POSITIVE SAM

SAM- RELATED CARBON BUDGET SUMMARY

Upwelling of DIC south of Polar Front≈balanced by northward Ekman transport and downwelling north of Polar Front

Changes in gas exchange and biological carbon export are of similar magnitude, but much smaller than advective changes

−1

T ^HE S ^OUTHERN O ^{CEAN IN A} H ^IGH -CO

W ^ORLD

CO₂uptake rate might grow slower than atm. CO₂

concentrations due to circulation changes as response to the positive SAM (Le Qu´er´e et al., 2007)

Anthropogenic ocean acidification will proceed, might even be amplified by upwelling of carbon-rich deep water (Lenton et al.,