Karel Castro-Morales 1* Jan Kaiser 1, Nicolas Cassar 2** and Deb Shoosmith 3 1 University of East Anglia, UK * now at: Alfred Wegener Institute, Germany 2 Princeton University, USA ** now at: Duke University, USA 3 British Antarctic Survey, UK Biological production and the influence of vertical physical processes in the Bellingshausen Sea

Bellingshausen Sea, West Antarctic Peninsula 90°W85°W80°W75°W70°W65°W60°W 67.5°S 70.0°S 72.5°S George VI Ice Shelf Wilkins Ice Shelf Alexander Island Antarctic Peninsula Eltanin Bay Ronne Entr. Adelaide Island Beeth. Pen. Latady Is. Charcot Is. Seawater temperature rise ~ 0.5 o C/decade in the upper 100 m (Meredith and King, 2005) D. R. Shoosmith Meredith et al., 2010

253 hydrographic stations (CTD-O 2 ) ADCP, ice cores, Drifters,  18 O (H 2 O) 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-O 2 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 O 2 (optode / Winkler) Gross O 2 production (dual-delta method; IRMS Kaiser, 2011) Biological O 2 flux (MIMS) Hendricks et al., 2004; Reuer et al., 2007 Luz and Barkan, 2000 & 2009 ≈ N≈ N k = 0.27( u 10 2 ) (Sc / 660) -0.5 (Sweeney et al., 2007) z mix ~ Ar O2O2 6CO 2 + 6H 2 O (+ light) C 6 H 12 O 6 + 6O 2 O2O2 Ar O2O2

z mix O2O2 O2O2 Ar  z mix Diapycnal flux (F v ) Entrainment (F e ) Contribution of physical effects in a mixed layer O 2 mass balance z mix ; c(O 2 ) > 0.5 % wrt 10 m (Castro-Morales and Kaiser, 2011) z mix –30 days = z mix_BM04 – 8 m (de Boyer Montegut et al., 2004)  z mix = z mix – z mix-30 days FvFv N Fe Fe + u + -

F bio (k w,  (O 2 /Ar)) F g (k w,  (O 2 )) outgassing ingassing WSIZ - Positive biological O 2 flux POOZ - “Negative” biological O 2 flux (?) mmol m -2 d -1 Total and biological sea-to-air O 2 fluxes

Brunt-Väisälä frequency (v 2 ) vs. F bio Vertical stability, enhanced by MW, as an important factor for the biological O 2 production (important source of nutrients and algae) 2 AASW MW Role of the vertical stability

Entrainment from the historical evolution of the mixed layer depth AASW AASW + WW MW  z mix (m) shallower deeper

Wilkins Ice Shelf Marguerite Bay 1 Belgica Trough Marguerite Bay 2 West Adelaide Island F bio FeFe FvFv N = F bio + F v + F e Flux / (mmol m -2 d -1 ) Contribution of physical effects to N F bio (mmol m -2 d -1 ) N=F bio +F e +F v (mmol m -2 d -1 ) WIS3839 MB12129 BT MB2-124 WAI-204

17  eq 17  G1G1 G2G2 G / (mmol m -2 d -1 ) 17  / (ppm) G / (mmol m -2 d -1 ) R 2 = 0.29 In WSIZ, contribution of MW with higher photosynthetic O 2. In POOZ possible entrainment of 17  stored in the WW due to deepening of z mix (WAI) G from two different pairs of 17  p and 18  p (Barkan and Luz, 2011; Kaiser and Abe, 2012) 17 O excess ( 17  ) from simple form: 17  17  –  17  eq = 0.6 T +1.8 (T in °C; Luz and Barkan, 2009) 17  max = 180 ppm 17  eq (T) = 1.6 ppm 17  air = 0 ppm

G / (mmol m -2 d -1 ) 65º 70º 75º 80º 85º 90º 95º 100º Longitude / (W) Hendricks et al., 2004 March, 2000 (70-65  S,  W) Comparison to other studies Huang et al., 2012 (north of our POOZ, peak of growing season) Off Marguerite Bay: 17  = (27±22) ppm Here (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” F bio. If not, misleading results or difficult to interpret. Contribution of upwelling and horizontal influence must be included Vertical measurements of O 2 /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

MCDW AASWMW Adelaide IslandAlexander Island WW  (O 2 ) (%) Latitude Alexander Is. Adelaide Is. MB2 MB1 MB2 MB1 oceanic shelf Marguerite Bay

RegionMethodCarbon unitsOxygen units This work Bellingshausen Sea (late summer – early autumn) O 2 /Ar and TOI N(C) = [N(O 2 )/1.4]  mg C m -2 d -1 (WSIZ) 36 mg C m -2 d -1 (POOZ) G( 14 C) = [G(O 2 )/2.7]x12 65 mmol m -2 d -1 (WSIZ) 48 mmol m -2 d -1 (POOZ) N(O 2 ) 53 mmol m -2 d -1 (WSIZ) 4 mmol m -2 d -1 (POOZ) G(O 2 ) 175 mmol m -2 d -1 (WSIZ) 131 mmol m -2 d -1 (POOZ) Boyd et al Bellingshausen Sea (late spring – early summer) O 2 bottle incubations N(O 2 ) 113 mmol m -2 d -1 (here WAI; 4 mmol m -2 d -1 Vernet et al., (2008) WAP - SIZ (January) 14 C incubations (1994 – 2008) NPP 745 mg C m -2 d -1 ( mg C m -2 d -1 ) Arrigo et al., (2008) Bellingshausen Sea Ocean color, SST and sea-ice concentration (1997 – 2006) NPP 316 mg C m -2 d -1 Agustí and Duarte (2005) Southern Ocean Mesocosm, O 2 incubations GPP (O 2 ) 100 mmol m -2 d -1

MUCDW MW AASW CDW Salinity WW

Castro-Morales and Kaiser, Ocean Science

Hystorical wind speed vs. ship winds

Monthly mean wind speed and direction (ECMWF, 6 hr resolution)

Continuous underway supersaturations WISMB1  O 2  Ar  O 2 /Ar BT WAI MB2 Sea Ice Zone Permanent Open Ocean Zone Alex. Is. Adel. Is. Alex. Is. Ch. Is. Lat. Is. Beeth.Pen.

Kz = 0.11  0.2 x m 2 s -1 SOIREE experiment Law et al., 2003 G from two different pairs of isotopic signals from photosynthetic activity G 1 (Barkan and Luz, 2011) 17  p = ‰ 18  p = ‰ G 2 (Kaiser and Abe, 2012) 17  p = ‰ 18  p = ‰

Sea Ice Zone: AASW MCDW Charcot IslandAlexander Island IW Latitude Longitude Alexander Island Wilkins Ice Shelf Charcot Is. Latady Is. Beethoven Pen. Vertical section in the SIZ Wilkins Ice shelf

West of Adelaide Island Permanent Open Ocean Zone Latitude Longitude Adelaide Is. WW AASW MCDW

Permanent Open Ocean Zone AASW c(O 2 ) 25 % of F bio FvFv 150 % of F bio FeFe WW (WAI) Sea Ice Zone 32 % of F bio (MB1) 25 % of F bio FvFv IW FeFe Horizontal advection of IW (Alexander and Charcot Islands) Net autotrophy > heterotrophy Entrainment of O 2 depleted waters (80 % contribution to negative F bio ) Physical processes (and net heterotrophy) > net autotrophy 17 O anomaly from remnant mixed layer (apparent autotrophy) Contribution of physical effects to NCP

O 2 mass balance (NCP and GOP) (O 2 /Ar and triple oxygen isotopes, TOI) (Craig and Hayward, 1987; Luz and Barkan, 2000) Gross production (carbon or oxygen) (GP) – total rate of O 2 or C production by all members of the community (autotrophy and heterotrophy) (i.e. phytoplankton, bacteria, algae, vascular plants) Net community production (carbon or oxygen) (NCP) – net metabolic balance between photosynthesis and respiration by all members of the community (production in mixed layer depth, mmol O 2 m -2 d -1 ) NCP = GOP – R Traditional methods for primary production estimates 6CO 2 + 6H 2 O (+ light) C 6 H 12 O 6 + 6O 2

Mixed layer O 2 mass balance Hamme and Emerson, 2002 Kaiser et al., 2005 FgFg F bubbles +-+- z mix FvFv - +  z mix FeFe +- F bio F bubbles ≈ F Ar ( < 1 % ) NCP ≈ F bio - F v - F e Biological O 2 = Physical O 2 F bio = F v + F e F bio z mix ; c(O 2 ) > 0.5 % wrt 10 m (Castro-Morales and Kaiser, 2011) z mix –30 days (de Boyer Montegut et al., 2004)  z mix = z mix-30 days – z mix X

Summary Sea Ice Zone Permanent Open Ocean Zone

c(O 2 ) (  mol kg ) Depth (m) zozo c base (O 2 ), z base c o (O 2 ), m z mix c zmix (O 2 ), c(O 2 ) (  mol kg -1 )