Karel Castro-Morales1* Jan Kaiser1, Nicolas Cassar2** and Deb Shoosmith3

1University of East Anglia, UK*now at: Alfred Wegener Institute, Germany

2Princeton University, USA**now at: Duke University, USA

3British Antarctic Survey, UK

Biological production and the influence of vertical physical processes in the Bellingshausen Sea

Bellingshausen Sea, West Antarctic Peninsula

90°W 85°W 80°W 75°W 70°W 65°W 60°W

67.5°S

70.0°S

72.5°S

George VI Ice Shelf

WilkinsIce

Shelf

AlexanderIsland

AntarcticPeninsula

Eltanin Bay

RonneEntr.

AdelaideIsland

Beeth.Pen.

LatadyIs.

CharcotIs.

Seawater temperature rise ~ 0.5 oC/decade in the upper 100 m (Meredith and King, 2005)

D. R. Shoosmith Meredith et al., 2010

253 hydrographic stations(CTD-O2)ADCP, ice cores,Drifters, 18O (H2O)

03/03/07 10/04/07

BT

WAI

MB2

WIS

MB1

Winter Sea Ice Zone (WSIZ)Wilkins Ice Shelf (WIS)

Marguerite Bay 1 (MB1)

Permanent Open Ocean Zone (POOZ) Marguerite Bay 2 (MB2)

Belgica Trough (BT)West Adelaide Island (WAI)

253 hydrographic stations, CTD-O2 and the different flavours of oxygen at the surface

3 March to 9 April, 2007 (38 days) - “RRS James Clark Ross”

Location of marginal ice zone and zonal separation

AMSR-E, Ice 0.3(Advanced Microwave Scanning Radiometer -

Earth Observing System, NASA)

Ice conditions during sampling

Station 10 (Wilkins Ice Shelf)

Marguerite Bay 1

Total sea-air flux of O2 (optode / Winkler)

Gross O2 production (dual-delta method; IRMS

Kaiser, 2011)

Biological O2 flux (MIMS)

Hendricks et al., 2004; Reuer et al., 2007Luz and Barkan, 2000 & 2009

)(O)O( 2eq2g cΔkF w

)(O/Ar)O( 2eq2wbio cΔkF ≈ N

k = 0.27( u102 ) (Sc / 660)-0.5

(Sweeney et al., 2007)

zmix ~ ArO2

6CO2 + 6H2O (+ light) C6H12O6 + 6O2

O2Ar

O2

18

18P

18

R17

17P

17

E18

RE17

218

eq1818

E18

R17

eq1717

E17

eqw

11

))((O1

)1(1

)1(

ckG

oxy

2zv

)(O

z

cKF

oxy

22

mixe

)(O)(

2

1

z

c

t

zF

zmix

O2

O2 Ar

zmix

Diapycnal flux (Fv)

Entrainment (Fe)

Contribution of physical effects in a mixed layer O2 mass balance

zmix ; c(O2) > 0.5 % wrt 10 m

(Castro-Morales and Kaiser, 2011)

zmix–30 days = zmix_BM04 – 8 m

(de Boyer Montegut et al., 2004)

zmix = zmix – zmix-30 days

Fv

evg2

mix

)(OFFFRG

t

cz

N

Fe

+

u

+ -

Fbio (kw, (O2/Ar))Fg (kw, (O2))

outgassing

ingassing

WSIZ - Positive biological O2 fluxPOOZ - “Negative” biological O2 flux (?)

mmol m-2 d-1 mmol m-2 d-1

Total and biological sea-to-air O2 fluxes

-5.E-05

0.E+00

5.E-05

1.E-04

2.E-04

2.E-04

3.E-04

3.E-04

-100 -50 0 50 100 150

F bio (mmol m-2 d-1)

N2(m

s-2

)

WIS

BT

MB1

WAI

MB2

Brunt-Väisälä frequency (v2) vs. Fbio

Vertical stability, enhanced by MW, as an important factor for the biological O2 production (important source of nutrients and algae)

2

25.4

25.6

25.8

26.0

26.2

26.4

26.6

26.8

27.0

27.2

27.4

-8 -6 -4 -2 0 2 4 6 8 10 12 14 (O2) (%)

Po

ten

tial d

en

sity

(kg

m-3

) +

10

00 WIS MB1 BT

WAI MB2AASW

MW

Role of the vertical stability

Entrainment from the historical evolution of the mixed layer depth

25.4

25.6

25.8

26.0

26.2

26.4

26.6

26.8

27.0

27.2

27.4

-20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45

zmix (m)

Po

ten

tia

l d

en

sit

y (

kg

m-3)

+ 1

00

0

WIS MB1 BT

WAI MB2

AASW

AASW + WW

MW

zmix (m)

shallower deeper

-80.0

-60.0

-40.0

-20.0

0.0

20.0

40.0

60.0

80.0

WIS MB1 BT MB2 WAI

Flu

x (m

mol

m2 d

-1)

FvFeFbioN(O2) = Fbio + Fe + Fv

WilkinsIce Shelf

MargueriteBay 1

BelgicaTrough

MargueriteBay 2

WestAdelaide

Island

Fbio Fe

Fv

N = Fbio + Fv + Fe

Flu

x / (

mm

ol m

-2 d

-1)

Contribution of physical effects to N

Fbio (mmol m-2 d-1) N=Fbio+Fe+Fv (mmol m-2 d-1)

WIS 38 39

MB1 21 29

BT -18 -12

MB2 -12 4

WAI -20 4

0

10

20

30

40

50

60

70

80

90

WIS MB1 BT MB2 WAI

17

/ (p

pm

)

0

50

100

150

200

250

G /

(mm

ol m

-2 d

-1)

D17eq D17

G1 G2

17eq 17G1

G2

G /

(mm

ol m

-2 d

-1)

17

/ (p

pm

)

R2 = 0.29

0

50

100

150

200

250

300

350

400

25.5 26.0 26.5 27.0 27.5

Potential density / (kg m -3) - 1000

G /

(m

mo

l m

-2 d

-1)

WISMB1BTWAIMB2

G /

(m

mo

l m

-2 d

-1)

R2 = 0.29In WSIZ, contribution of MW with higher photosynthetic O2.

In POOZ possible entrainment of 17 stored in the WW due to deepening of zmix (WAI)

G from two different pairs of 17p and 18p (Barkan and Luz, 2011; Kaiser and Abe, 2012)

17O excess (17) from simple form:1717– 0.517918

17eq = 0.6 T +1.8(T in °C; Luz and Barkan, 2009)

17max= 180 ppm

17eq (T) = 1.6 ppm

17air = 0 ppm

0

50

100

150

200

250

300

350

400

65.0 70.0 75.0 80.0 85.0 90.0 95.0 100.0

Longitude West

G(O

2)

(mm

ol m

-2 d

-1)

WIS

MB1

BT

WAI

MB2

H04_dualdelta

H04

G /

(m

mo

l m

-2 d

-1)

65º 70º 75º 80º 85º 90º 95º 100ºLongitude / (W)

Hendricks et al., 2004March, 2000

(70-65 S, 98-67 W)

Comparison to other studies

Huang et al., 2012 (north of our POOZ, peak of growing season) Off Marguerite Bay: 17= (27±22) ppmHere (WAI): 17= (24±10) ppm(Lack of 17 and 18 data from supplementary material)

• Physical effects must not be neglected in future corrections to N (and G). Can account for large portion of “negative” Fbio. If not, misleading results or difficult to interpret.

• Contribution of upwelling and horizontal influence must be included

• Vertical measurements of O2/Ar and TOI must be considered

• As sea-ice melt water increases in the Bellingshausen Sea continental shelf, the variability of the marine productivity will be also affected (longer phytoplankton growing periods) with possible increase in carbon export to deep ocean

Castro-Morales et al., 2013, Biogeosciences

Summary

Acknowledgements

National Council for Science and Technology (CONACyT)Mexico

A. Jenkins (BAS) Antarctic Climate and the Earth System Forcings from the Oceans, Clouds, Atmosphere and Sea-ice (ACES-FOCAS) (JR165)

NERC

M. Bender (PU); NSF and NASA