USCG Polar Star overview &

Particle export during SOFeX

Ken O. Buesseler

Operation personnel, etc.

Export- 234Th WHOI w/on board detectors- K. Buesseler & S. Pike

SF6 WHOI/UEA UK (J. Ledwell, A. Watson)- L. Houghton & L. Goldson

surf. water pCO2 AOML install prior to departure in Seattle(R. Wanninkhof)

Major Nutrients To collect & freeze for later analyses (ancillary team- C. Herbold, K. Mahoney, J. Tegeder, M. Coggeshall)Particles, small

volume- POC/PON/bSi & pigments

WHOI to collect for CHN & bSi (M. Brzezinski- UCSB); pigments (frozen for R. Bidigare, U. Hawaii); C/N isotopes (for M. Altabet)- Ancillary teamParticles, large

volume- 234Th, C/N isotopes

share between Buesseler & Altabet for 234Th & stable C/N work- K. Buesseler & S. Pike

DIC/DOC Collect & return for on shore analyses (F. Millero- U Miami/J. Bauer-VIMS)- R. Daniels

Iron Fe dissolved, total & speciation from Kevlar/bottles & towed fish (P. Croot- IfM & R. Frew- U. Otago, NZ)

Production- primary &bacterial

14C and 3H- (W. Smith-VIMS/R. Barber- Duke and H. Ducklow- VIMS)- C. van Hilst, R. Daniels

Biological Fe stress Fv/Fm- P. Boyd & E. Abraham (NZ)

others salinity, radium (Herbold), bio (chl-C. van Hilst)

Polar Star Science team

Polar Star cruise- 10 profile stations; 6 In, 4 Out

-67.0

-66.5

-66.0

-65.5

-65.0

-173 -172 -171

B1

BC2

CTD 2

B3

CTD 4

CTD 6

B4

B5

B6

CTD 5

BC1

BC2

BC3

CTD2

CTD4 CTD6

6 “In” profiles- 5 at highest SF6; 1 shoulder sta.

SF6Goldson et al.

65 S

67.5

170 W172 W

SOFeX patch as seen from space 4 weeks after iron fertilization

SeaWiFS ocean color

Satellite image- Feb. 12, 2002, F. Chavez et al.

SOFeX patch seen as SF6 peak & Fv/Fm peakThorium-234 indicates similar particle flux in & out of patch (C flux may be elevated, but didn’t see diatom crash)

Calculate Calculate 234234Th flux from the measured Th flux from the measured 234234Th Th activitiesactivities

Low Low 234234Th = High fluxTh = High flux

Prior Fe Fertilization export data:Prior Fe Fertilization export data:FeEX-II: 6 surface samplesFeEX-II: 6 surface samplesSOIREE: 1 5pt profile and & time-series integralsSOIREE: 1 5pt profile and & time-series integrals(better coverage for EISENEX & SERIES?)(better coverage for EISENEX & SERIES?)

Thorium-234 approach for estimating particle exportThorium-234 approach for estimating particle export

half-life = 24.1 dayshalf-life = 24.1 days

source = source = 238238U parent is U parent is conservativeconservative

sinks = attachment to sinking sinks = attachment to sinking particles and decayparticles and decay

depthdepth(m)(m)

[234Th]

238U

Melville Feb 3 transect

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-66.4 -66.2 -66.0 -65.8

Latitude

23

4T

h (

dp

m/l

@2

0m

)

0.000

10.000

20.000

30.000

40.000

50.000

SF

6 (

fM)

Thorium

SF6

updated 8/16/02

Melville Feb 13/14 transect

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-173.0 -172.5 -172.0

Latitude

234T

h (

dp

m/l

@

20m

)

0.00

5.00

10.00

15.00

20.00

SF

6 (f

M)

Thorium

SF6

updated 8/16/02

South to North transect Feb. 18, Polar Star

0

1

2

3

4

5

6

-66.6 -66.1 -65.6

Latitude

SF

6 (f

M)

or

234T

h

tota

l (d

pm

/l)

0

0.2

0.4

0.6

0.8

1

Flu

(sh

ips)

SF6

234Th

Fluupdated 8/16/02

West to East transect Feb. 21, Polar Star

0

1

2

3

4

-173 -172 -171

Latitude

SF

6 (

fM)

or

23

4T

h

tota

l (d

pm

/l)

0

0.2

0.4

0.6

0.8

Flu

(s

hip

s)

SF6

234Th

Flu

updated 8/16/02

SOFeX time-series progression S-patch"In" stations

Thorium-234 (dpm/l)

1.4 1.6 1.8 2.0 2.2 2.4

Dep

th (

m)

0

20

40

60

80

100

120

140

Jan. 30Feb. 4Feb. 8Feb. 10Feb. 14Feb. 15Feb. 15Feb. 16Feb. 17Feb. 19Feb. 20238U

Highest resolution thorium-234 data setHighest resolution thorium-234 data set

See progression to lower Thorium-234 on See progression to lower Thorium-234 on average during course of SOFeX “In” patch (and average during course of SOFeX “In” patch (and “Out” stations also)“Out” stations also)

Southern Patch time-series average 0-50m Thorium activity

Days post initial Fe

0 5 10 15 20 25 30Th

ori

um

-234

avt

ivit

y 0-

50m

avg

(d

pm

l-1)

1.2

1.4

1.6

1.8

2.0

2.2

234Th In (w/o last Melville sta)

In Regr dTh/dt = 2.22 -0.026(day) r^2 = 0.97

In 95% conf

234Th out

Out Regr dTh/dt = 1.97 -0.01(day) r^2=0.77

Out 95% conf

last Melville "In" sta (not used in regression)

234Th/t = (238U - 234Th) - PTh + V

where decay rate; PTh = 234Th export flux; V = sum of advection & diffusion

In

Out

Southern Patch time-series Thorium flux

Days post initial Fe

0 5 10 15 20 25 30

Th

ori

um

-234

flu

x (d

pm

m-2

d-1

)

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

Out NSS model

In NSS model

Thorium-234 flux increasing both “In” and “Out”, but Thorium-234 flux increasing both “In” and “Out”, but significantly larger increased particle flux in Fe fertilized significantly larger increased particle flux in Fe fertilized patchpatch- first time that we see So. Ocean export response to Fe!- first time that we see So. Ocean export response to Fe!

S-patch In data only

0.0

5.0

10.0

15.0

20.0

26-Jan-02

2-Feb-02

9-Feb-02

16-Feb-02

23-Feb-02

C/T

h (

uM

/dp

m)

0-50m C/Th

50-100m C/Th

S-patch Out data only

0.0

5.0

10.0

15.0

20.0

26-Jan-02

2-Feb-02

9-Feb-02

16-Feb-02

23-Feb-02

C/T

h (

uM

/dp

m)

0-50m C/Th

50-100m C/Th

POC export = POC export = 234234Th flux • [POC/Th flux • [POC/234234Th ]Th ]sinking particlessinking particles

See references by: See references by:

Buesseler, Bacon, Benitez-Nelson, Cai, Charette, Cochran, Coppola, Dunne, Guo, Buesseler, Bacon, Benitez-Nelson, Cai, Charette, Cochran, Coppola, Dunne, Guo, Gustafsson, Hall, Langone, Miller, Moran, Murray, Pates, Roy-Barman, Rutgers vd Gustafsson, Hall, Langone, Miller, Moran, Murray, Pates, Roy-Barman, Rutgers vd Loeff, Santschi, Sarin, Shimmield, Smith, Wei & more …..Loeff, Santschi, Sarin, Shimmield, Smith, Wei & more …..

>53um particles: C/Th below 50m relatively constant>53um particles: C/Th below 50m relatively constant- used in POC flux calculations- used in POC flux calculations

Some evidence of increase C/Th “In” stations 0-50mSome evidence of increase C/Th “In” stations 0-50m- growth of phyto?- growth of phyto?

Southern Patch time-series POC flux @50m

Days post initial Fe

0 5 10 15 20 25 30

PO

C f

lux

@50

m (

mm

ol C

m-2

d-1

)

6

7

8

9

10

11

12

In NSS model (C/Th = 4.2)

Out NSS model (C/Th = 5.6)

POC flux “In” increased from 7-8 to 11 mmol C m-2 d-1POC flux “In” increased from 7-8 to 11 mmol C m-2 d-1- calculated at 50m- calculated at 50m

Did not see “crash” of Fe induced bloomDid not see “crash” of Fe induced bloom- flux still increasing; high Fv/Fm; still Fe….- flux still increasing; high Fv/Fm; still Fe….

Does iron fertilization lead to carbon sequestration into the deep ocean via sinking particles?

FeExII- significant C flux (12 days)

SOIREE- little/no C flux (13 days & satellite 55 days)

EisenEx – little/no “C flux” (22 days)

- lack of in/out differences (thorium-234)

SOFeX- small C flux increase (27.5 days since t^0)

- enhanced export “in” vs “out” (subtle changes)

- did not see crash of Fe induced (or natural) bloom

- maintained high photosynthetic efficiency

- low loss terms imply efficient recycling of iron

SOFeX time-series progression S-patch"Out" stations

Thorium-234 (dpm/l)

1.4 1.6 1.8 2.0 2.2 2.4

Dep

th (

m)

0

20

40

60

80

100

120

140

Jan. 31Feb. 1Feb. 5Feb. 12Feb. 17Feb. 18Feb. 19238U

SOFeX time-series progression N-patch"In & Out" stations

Thorium-234 (dpm/l)

1.4 1.6 1.8 2.0 2.2 2.4

Dep

th (

m)

0

20

40

60

80

100

120

140

In Jan. 24Out Jan. 25In Feb. 19Out Feb. 20238U

N-patch: see no clear in vs. out or time-series trendN-patch: see no clear in vs. out or time-series trend? hint at 10-20m on Feb. 19? hint at 10-20m on Feb. 19thth

? late station with lower PProd & Chl than Revelle? late station with lower PProd & Chl than Revelle