Observation of Net Community and Export Production from Autonomous Platforms

Todd Martz

OCB Floats and Gliders Workshop Moss Landing 2009

CollaboratorsKen Johnson (MBARI)Steve Riser (UW)Mike DeGrandpre (U. Montana)

Production

•Fluorescence Perry et al. 2008 ◘Davis et al. 2008 ◘Boss et al. 2008 ◘Niewiadomska et al. 2008 ◘

•OxygenKortzinger et al. 2004Riser and Johnson 2008Nicholson et al. 2008 ◘

•Beam attenuation / OBSBishop et al. 2002, 2004, 2009; Boss et al. 2008 ◘

•Oxygen (OUR)Martz, Riser Johnson, 2008◘

Export

Optical propertiesChemical properties

TOPICS

◘ L&O 53 (5, part 2) Special Issue on ALPS

Production, Respiration & Export

CO2 + NO3 + PO4 + H2O = Org + O2

Rate of metabolism0

dept

h (m

)

0

50

100

150

200

250

300NCPNCR

Observation of a reactant or product required to estimate rates of Net Community Metabolism & Export.

Rate of metabolism0

dept

h (m

)

0

50

100

150

200

250

300NCPNCR

We have poor spatial coverage of NCP and Export

Sat

ellit

e co

lor

Sedim

ent traps

Resolving the global carbon

budget

“The first task is to ensure that appropriate observational systems are put in place to permit accurate quantification of the oceanic carbon sinks and detect changes reliably”-N. Gruber

“The first task is to ensure that appropriate observational systems are put in place to permit accurate quantification of the oceanic carbon sinks and detect changes reliably”-N. Gruber

We need reliable sensors operating on autonomous

platforms!

Lagrangian measurement of Export

nDIC

NBSTs avoid sampling bias and allow shallower deployments

Ship required for recovery and subsequent analysis of particles

Rate of metabolism0

dept

h (m

)

0

50

100

150

200

250

300NCPNCR

Autonomous measurement

of NCP & export

dept

h

POC mmol m-3

170 180 190 200 210 220 230

10

20

305

10

15

20

25

30

35

30

25

20

15

10

5

dept

h (m

)

230220210200190180170

yearday

2060

2080

2100

2120

2140

DIC

Martz, DeGrandpre, Strutton, McGillis, Drennan. 2009. Sea surface pCO2 and carbon export during the Labrador Sea spring-summer bloom: an in situ mass balance approach, JGR Oceans, accepted.

Rate of metabolism0

dept

h (m

)

0

50

100

150

200

250

300NCPNCR

CO2 + NO3 + PO4 + H2O = Org + O2

∆DOC:NCP = 0.1Hansell & Carlson (1998)Teira et al. (2001)PIC:POC = 0.025Milliman et al. (1999)

Assumptions/simplifications

Fadv = 0

Labrador Sea Carbon Budget

a

PO

C (

mm

ol C

m-2

)

100

200

300

400

500

600

700

800

chl-a

(m

g m

-2)

0

50

100

150POC 0-35mChl-a 0-20m

b

NC

M &

∆P

OC

(m

mol

C m

-2 d

-1)

-50

0

50

100

150

200

250

PWP daily NCMPWP hourly NCMcarbon budget NCM∆POC

c

yearday (2004)

170 180 190 200 210 220 230

Φ (

mm

ol C

m-2

d-1

)

-100

-80

-60

-40

-20

0

20

Φ 7-day averageNABE average flux at 35m

∆DIC

+ ∆POCsus

+ ∆DOC

+ ∆PIC

+ ΦPOC

+ Fgas

+ Fent

+ Fadv

= 0

∆DIC

+ ∆POCsus

+ ∆DOC

+ ∆PIC

+ ΦPOC

+ Fgas

+ Fent

+ Fadv

= 0

C mass balance

Several other examples of mooring-based work…rest of talk focuses on ALPS

Observations of Fluorescence from ALPS

Bishop et al., 2004 -SOFEX

Martz, Riser, Johnson, 2008Gliders in CCS - Davis et al. (2008)

•Float in NA – Boss et al. (2008)

•Excellent for: establishing bloom timing, extent, intensity, duration; Ground truthing and filling in gaps in satellite data; identifying spatial patterns due to e.g. fronts/eddies.•Conversion of data into quantitative rates of NCP still elusive.

Gliders in MS - Niewiadomska et al. (2008)

Gliders off WA – Perry et al. (2008)

Bio-optical observations of export from floats

Bishop et al., 2004 -SOFEX

Martz, Riser, Johnson, 2008

Light side scattering sensor (POC proxy) Boss et al. (2008)

Export observed in eddy using integrated LSS – not found in fluorescence from satellite or float.

Bio-optical observations of export from floats

Bean attenuation (POC proxy, CFI – carbon flux index)Bishop et al. 2002, 2004, 2009 in press

Bishop et al., 2004 -SOFEX

Figure 2A from Bishop et al. 2004SOFeX float 2104

•During bloom, 2 µM → 9 µM POC and deepening of 1 µM contour clearly indicate growth and export.•Possible to estimate export flux from CFI or changes in integrated POC standing stocks.

Autonomous measurements of NCP and Export using oxygen sensors on floats and gliders

Martz, Johnson & Riser (2008)

Riser & Johnson (2008)

CO2 + NO3 + PO4 + H2O = Org + O2

Nicholson et al (2008)

NCP from O2 on gliders

Glider data from Nicholson et al. (2008) 0.6-1 mol C m-2 yr -1 (DEZ)

Profiling float data from Riser and Johnson (2008)1.6 mol C m2- yr-1 (EZ)

•Data collected near the Hawaii Ocean Time Series on autonomous platforms observe oxygen production in the deep euphotic zone.•Mass balance calculations used to calculate NCP agree reasonably well with historical data.

Consumption zone SOM at 43 oS

NCP and export from O 2 on floats

144oW 44oS (WMO 5901048)

0

20

40

60

80

100

120

140

160

Oct-05 Jan-06 May-06 Aug-06 Nov-06 Feb-07

dept

h (m

)

MLD

Zc

Production zone SOM at 22 oN22oN 158oW (WMO 4900093)

0

20

40

60

80

100

120

140

160

Dec-02 Jun-03 Jan-04 Aug-04 Feb-05 Sep-05

dept

h (m

)

MLD

Zc

•Annual pattern changes with latitude•Observe some NCP at low latitude•Observe some EP at high latitude

8/02 8/03 8/04 8/05

O2

(µm

ol/k

g)

190

200

210

220

7/03 7/04 7/05 7/06

O2

(µm

ol/k

g)

190

200

210

220

a b

78 m 87 m

22oN 22oS 43oS

Rate of metabolism0

dept

h (m

)

0

50

100

150

200

250

300NCPNCR

Seasonal observations O 2

Low latitude NCP partially observed (Riser & Johnson, 2008)

High latitude EP partially observed (Martz, Riser & Johnson, 2008)

11/05 11/06

[O2]

(µm

ol k

g-1)

240

250

260

270

280

290

Remineralization rates at 43 oS

Martin et al. (1987)

Derivative of the particle flux attenuation function

Martin ‘b’ exponent found using binned oxygen rates appears to be larger than trap-based values (usually -1.3 to -0.6).

This can be reconciled by: oxygen gradients, trapping efficiency, active transport.C remineralization rate

(µmol C kg-1 year-1)

0 2 4 6 8 10 12 14

dept

h (m

)

0

200

400

600

800

Argopower law fit, b = -0.2

C remineralization rate

(µmol C kg-1 year-1)

0 2 4 6 8 10 12 14

dept

h (m

)

0

200

400

600

800

ArgoFeely et al. (2004)power law fit, b = -0.2

Net Community Production (mmol C/m3/y)

0 5 10 15 20 25

Dep

th (

m)

0

50

100

150

200

Summary of rates calculated

Low productivity STG

Intense SOM allows estimates of NCP above Zc

Higher productivity region (STF)

Substantial vertical export/transport of organic matter allows estimates of EP below Zc

C remineralization rate

(µmol C kg-1 year-1)

0 2 4 6 8 10 12 14

dept

h (m

)

0

200

400

600

800

ArgoFeely et al. (2004)power law fit, b = -0.2

Floats are located in a transition region between the permanently stratified, oligotrophic South Pacific subtropical gyre and the seasonally stratified, mesotrophic South Pacific

Sarmiento, J. L.; R. Slater, R. Barber, L. Bopp, S. C. Doney, A.C. Hirst, J. Kleypas, R. Matear, U. Mikolajewicz, P. Monfray, V.Soldatov, S. A. Spall, and R. Stouffer. 2004. Response of oceanecosystems to climate warming. Global Biogeochem. Cycles. 18: GB3003, doi:10.1029/2003GB002134.

Spatial trends at 42 oS

X Data

mm

ol C

m-2

day

-1

0

20

40

60

80

NPPEP

longitude (degrees west)

100120140160180

NP

P (m

mol

C m

-2 d

ay-1

)

30

40

50

60

70

80

EP

(mm

ol m

-2 d

ay-1

)

0

5

10

15

20

25NPP averagedEP averaged

Pacific Profiling Float: Physical model

SST

(o C

)8

10

12

14

16

Argomodel

time

Nov Mar Jul Nov Mar

dept

h (m

)

0

30

60

90

120

150

a

b

ZC

•PWP does a reasonable job of reproducing the annual temperature and mixed layer depth

•Compensation depth, Zc, is calculated from the Ic of Siegel et al. (2002) and the incident radiation from NCEP

Float 5901048 (45oS 144oW )

•PWP model of mixed layer physics with biology added (Musgrave et al., 1988). •NCP constrained by measured data (model solves for NCP using a least squares fit).

Float 1D Model

[O2]

(µm

ol k

g-1)

240

260

280

300

Argomodel

[O2]

(µm

ol k

g-1)

240

260

280

300

[O2]

(µm

ol k

g-1)

260

280

75 m

0 m

a

b

c

time

Nov Mar Jul Nov Mar

[O2]

(µm

ol k

g-1)

240

260

280

35 m

d

125 m

Model NCP = 2.1 mol C m-2 yr-1

EP50-900 for float 5901048:

year 1 = 2.0 mol C m-2 yr-1

year 2 = 3.0 mol C m-2 yr-1)

Consumption zone SOM

Model explains erosion of SOM due to MLD-Zc proximity

8

time

Nov Mar Jul Nov Mar

dept

h (m

)

0

30

60

90

120

150b

ZC

c) ASIS

180 200 220

pCO

2 (µ

atm

)

220

240

260

280

300

320

340

360

380

a) ASIS

180 200 220

tem

pera

ture

(o C

)

6

8

10

12

d) PWP-CO2

yearday180 200 220

pCO

2 (µ

atm

)

220

240

260

280

300

320

340

360

380

b) PWP-CO2

yearday180 200 220

tem

pera

ture

(o C

)

6

8

10

12

3m5m9m20m35m

PWP model adapted to CO 2 for Labrador Sea ASIS

Expect: Increased number of optical and chemical (O2, NO3-, pH)

sensors on floats and other autonomous platforms.

What should be done?-Quality control of chemical data at Argo data centers is not currently supported…

-Modelers need to begin thinking about integrating float data into regional models.

-Sensor developers need to continue to improve sensor performance.

What Next?CO2 + NO3 + PO4 + H2O = Org + O2

ISFET ISUS