Carbonate counter pump s/mulated by natural iron fer/liza/on in the Polar Frontal Zone

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Carbonate counter pump s/mulated by

natural iron fer/liza/on in the Polar Frontal Zone

Ian Salter*, Ralf Schiebel, Patrizia Ziveri, Aurore Movellan, Richard Lampi>, George Wolﬀ

*Alfred-‐Wegner-‐Ins.tute for Polar and Marine Science, Bremerhaven, Germany

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INTRODUCTION AIMS METHODS RESULTS & DISCUSSION

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CaCO₃ producMon in the surface and transport to depth increases atmospheric CO₂.

On millenial Mme-‐scales CCP leads to shiRs in the verMcal distribuMon of TCO₂ and TA

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Constrain the opposing eﬀects of these counter-‐acMng components of the biological carbon pump

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Island-‐associated blooms in Southern Ocean

Iron-‐supply enhances ecosystem producMvity and POC export

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Pollard et al. 2009 Nature

[+Fe]-‐ferMlized bloom to the North; [HNLC] to the south

+Fe

HNLC

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POC ﬂuxes enhanced by a factor of ~2-‐3 as a result of iron ferMlizaMon

Driven by resMng spore formaMon of Eucampia antarc.ca var antarc.ca

Salter et al. 2012 Glob. Biogeo Cy.

+Fe HNLC

E. antarc)ca var. antarc)ca

Organic carbon pump

~x2

~x3

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POC ﬂuxes enhanced by a factor of ~2-‐3 as a result of iron ferMlizaMon

Driven by resMng spore formaMon of Eucampia antarc.ca var antarc.ca

Salter et al. 2012 Glob. Biogeo Cy.

+Fe HNLC

E. antarc)ca var. antarc)ca

Organic carbon pump

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-‐ Annual CaCO₃ ﬂuxes were 7-‐10 Mmes higher in [+Fe] regime

-‐ Large excess CaCO₃ ﬂuxes than excess POC ﬂuxes : POC:PIC ra/o

POC ﬂux

2-‐3 fold increase

+Fe HNLC

~x7 ~x10

+Fe +HNLC

Inorganic carbon pump

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(1)   How are CaCO

₃

ﬂuxes distributed across diﬀerent calcifying groups?

(2) How signiﬁcant is the carbonate counter pump for iron-‐ferMlized sequestraMon of atmospheric CO

₂

?

INTRODUCTION AIMS METHODS RESULTS & DISCUSSION

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(1)   How are CaCO

₃

ﬂuxes distributed across diﬀerent calcifying groups?

(2) How signiﬁcant is the carbonate counter pump

for iron-‐ferMlized sequestraMon of atmospheric CO

₂

?

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Methods:

Coccolith-‐derived CaCO₃ -‐ ﬁne-‐fracMon (< 20 um and 20-‐63 um) Ca (ICP-‐AES) Pteropod species enumerated, removed and weighed with fragments

Foraminifera – automated image analysis (63-‐100 and >100 um) Manual species ID.

Coccolith Foraminifer Pteropods

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Foraminifer dominate CaCO₃ﬂux (35-‐50%)

Largest relaMve diﬀerence

in pteropod ﬂux

Excess PIC ﬂuxes >

excess POC ﬂuxes in all fracMons

Salter et al. 2014 Nat. Geosci.

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in pteropod ﬂux

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in pteropod ﬂux

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in pteropod ﬂux

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Foraminifer dominate CaCO₃ﬂux (35-‐50%)

Largest rela/ve diﬀerence

in pteropod ﬂux

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Foraminifer dominate CaCO₃ﬂux (35-‐50%)

in pteropod ﬂux

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N. Pachyderma dominate foram-‐CaCO₃ fracMon

Larger species more important at iron ferMlized site

Changes in foram-‐CaCO₃: (i) increase producMon (ii) assemblage shiRs

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(1)   How are CaCO

₃

ﬂuxes distributed across diﬀerent calcifying groups?

(2) How signiﬁcant is the carbonate counter pump

for iron-‐ferMlized sequestraMon of atmospheric CO

₂

?

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Atmosphere Surface Ocean

Deep-Ocean

CO₂

(i) Removal of CO₂ plankton POC export – biological carbon pump (ii) Production of CaCO₃ above ventilation depth - conservative

Ventilation depth

(iii) POC:PIC ratio

(v) Ψ = CO₂ released:CaCO₃ precipitated

No correction For dissolution

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Atmosphere Surface Ocean

Deep-Ocean

CO₂

(i) Removal of CO₂ plankton POC export – biological carbon pump (ii) Production of CaCO₃ above ventilation depth - conservative

Ventilation depth

(iii) POC:PIC ratio

(v) Ψ = CO₂ released:CaCO₃ precipitated

No correction For dissolution

1. {[(gross CO₂ sink)-‐(net CO₂ sink)]/(gross CO₂ sink)}* 100 2. Gross CO₂ sink= (FPOC_WML)

3. Net CO₂ sink = [(FPOC_WML) -‐ (FPIC_WML x Ψ )

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Expressed as % reducMon in deep-‐ocean CO₂ storage

CCP eﬀect: 6-‐32% in [+Fe] region 1-‐4% in [HNLC] region

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Importance of bloom locaMon

SAF transiMon from Si to CaCO₃ dominated producMon/export Si:PIC raMos characterisMc of PFZ

Salter et al. 2014 Nat. Geosci. SI

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[+Fe] PFZ unique : opal dominated export, excess PIC over POC ﬂuxes

CCP due to increases in PIC producMon/transport relaMve to both Si and POC

Southern Ocean data compila)on

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Salter et al. 2014 Nat. Geosci. Opal

CaCO₃

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CaCO₃ POC

PIC

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CaCO₃ POC

PIC

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CaCO₃ POC

PIC

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CaCO₃ POC

PIC

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SUMMARY and Acknowledgements [+Fe] enhances CaCO₃ ﬂux in PFZ

Foraminifer dominant CaCO₃ ﬂux fracMon

EﬀecMve CO₂transfer by BCP may be reduced 10-‐30%

POC:PIC < 1 in Si:PIC>1 unique to polar frontal zone iron ferMlizaMon

Further Acknowledgments -‐ Raymond Pollard (NOC) -‐ Richard Sanders (NOC)

Thank you for your a_en/on

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Test-‐size distribuMons

Size-‐normalized test weights

Foram-‐CaCO₃ ﬂux

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LGM increases in export occurred in sub-‐antarcMc zone

Increases in OC export were possibly accompanied by a strengthened carbonate counter pump

Decreased signiﬁcance of BCP for regulaMng glacial Interglacial tranisiMons in atmospheric CO₂

Kohfeld et al. 2005 Science

MarMnez-‐Garcia et al. 2014 Science

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Southern Ocean data-‐set compiled

Classiﬁed in rela/on to frontal posi/on

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-‐6 -‐4 -‐2 0 2 4 6 8 10 12 14

Increase with depth

POC:PIC Increase with depth

72%

28%

POC:PIC increase with depth

POC:PIC decrease with depth

POC:PIC CHANGES WITH DEPTH FROM MULTI-‐TRAP DEPTH MOORINGS

Carbonate counter pump s/mulated by natural iron fer/liza/on in the Polar Frontal Zone