What is the upper limit for primary production in the Southern Ocean?

30oS

40oS

50oS

60oS

70oS180oW 120oW 60oW 0o 60oE 120oE 180oE

(d’après Pollard et al., 2007)

C. Guinet, S. Renaut,H. Claustre, X.Xing

N. MetzlC. LoMonaco

Stéphane Blain, Laboratoire d’Océanographie Microbienne,

Université Pierre et Marie Curie ,CNRS, Banyuls/mer, France

Above the kerguelen plateau the interannual variability of Net community Production (NCP) and air-sea CO2 flux

was < 15 %

CTD FLUO Tag

- Temperature

- Salinity

- Fluorescence

1 or 2 profiles/day (18 points per profiles)

Elephant seals of Kerguelen(Mirounga Leonina)

21 animals between 2008 and 2011

Calibration methods inXing et al. L&O methods 2012Guinet et al. ESSD 2013

Climatology in the antarctic zone (between polar front and Southern Antarctic Circumpolar Current Front )

PARML=1/MLD

Control of integrated chlorophyll by self-shading.

The end of the bloom: why?

observed

PARML= 3.5 mol photon d-1

observed

calculated

PARML= 2.5 mol photon d-1

EIFEX (Smetacek et al. 2012)

KEOPS2

Oct-Nov 2011 (KEOPS2)

Feb 2012 (OISO 21)

Low silicic acid concentrations limit diatom growth at the end of the bloom.

3000 values between 1992 and 2012(depth > 900 m) from OISO (C. Lo Monaco)

Preliminary result˗1.0 ± 0.2 mol C m-2 y-1

air sea CO2 flux

CARIOCA buoy deployed during KEOPS2 (J. Boutin)

Summary :

In naturally iron fertilized regions the amount of chlorophyll that accumulates in the mixed layer is controlled by self-shading

Considering self shading control, chlorophyll in the mixed layer could be higher and therefore theCO2 sink could be deeper.

Possible :

If silicic acid supply increases

If Si/C of diatoms decreases