reducing uncertainty in satellite ocean color products with measurements made from gliders and floats

M.J. Perry, UMaine Herve Claustre, LOVKen Johnson, MBARI

Craig Lee & Eric D’Asaro, UWEmmanuel Boss, UMaine

Brandon Sackmann, WDOE

NASA Ocean Color Research Team Meeting 4-6 May 2009, New York City

The ocean below –

What can gliders and floats do for NASA’s Ocean Biology and Biogeochemistry Program ?

CSZC in 1978: first ‘big’ picture, synoptic view ––> major advances in understanding phytoplankton processes, inter-annual variability, bio-physical connectivity, global primary production, etc.

‘Arrays’ of gliders and floats: * persistent presence (unlike ships) * spatial information (unlike moorings) * vertical presence (unlike satellites)

Combined sensing w / satellites ––> new opportunities for major advances

Update since ALPS meeting in 2003– Iridium 2-way communications– unattended

Gliders (directional, but slow) – long endurance ~ 9.5 mo.– depths to 1,000+ m; hurricanes – 450 miles under ice– always adding new sensors

Floats (go w/ the flow; diversity)

– bio-ARGO floats, 3+ yr – Lagranigan floats, pick- up truck

load of bio-optical & other sensorsSensors –– need to be small, low-power, robust; issues of cal, drift,

fouling: CTD, chl and CDOM fluorescence, optical backscatter (), beam c, O2, nitrate, PAR, Ed (), Lu (), LOPC, sediment traps, turbulence, current meter, carbon flux, PIC, etc. Near term, add other C-cycle sensors.

1) Data even when cloudy, vertical distribution of variables, mixed layer depth, etc.

2) Validation of remote sensing products (requires calibrated sensors)Temp, optical backscatter, radiances (physical properties; SI

units);S – own issues; CDOM (requires conversion from F to

absorption); Chl (requires fluorescence quench correction or 3-absorption)

3) Validation of biogeochemical models by providing link between in situ processes and satellite-based models:

primary productivity – improved input to biomass/light models: validate biomass and provide vertical distribution of biomass; PS coefficients (Cullen approach for Ek from fluorescence)particle production – diel changes in particles (bb, c, LOPC, etc.)

net community production from changes in O2 and other stoichiometric conversions – nitrate drawdown (pCO2……)role of physics in export and other processes

4) Discovery – of unexpected or unknown phenomena and/or forcings

Reducing uncertainty in ocean color products

1a) Data even when cloudy – satellite & gliders subpolar N.A.

100% clear NAB08 – D’Asaro, Lee, Sackmann Perry, Fennel

50

25

1b) Vertical distribution of biomass & mixed layer depth

Seaglider off Washington –Perry, Sackmann, Eriksen, Lee (2008) L&O sp. issue

Density

Chlorophyll

January through Nov 2004

2) Validation of remote sensing products

Motivation:

* S. Maritorena’s talk yesterday on MEASURES products and links to biogeochemical products.

* Proxy relationships:

bb and c to POC

particle size and species

detrital material, CDOM, DOC

First, need validation of primary products (bb, etc.)

T & S & density bb Ed c 412 chl 490 CDOM 555

Boussole mooring

PROVBIO : PROVOR float in Mediterranean Sea; 22 May 2008

2) Validation of remote sensing products

Claustre et al., unpub.

Advantage of deploying w/ reasonable accessibility to validate sensors while learning (location, location, location)

2) Toward validation of remote sensing products

Bio-optical ARGO float – 3+ years in Labrador Sea

Boss et al. 2008

Hybrid ‘validation’ – need to move toward better sensor calibrations and cross calibrations

fluorescence

absorption

CDOM absorption is a primary ocean color variable, butCDOM fluorescence requires conversion to absorption

What sensors? How to quantify relationships?

2) Toward validation of remote sensing products

Is there a better in situ sensor?

CDOM a-meter?

Chlorophyll absorption is a primary ocean color variable, butfloat and glider sensors measure chlorophyll fluorescence.

Requires conversion from fluorescence to chlorophyll concentration (but that is still not absorption)

What sensors? How to quantify relationships?

2) Toward validation of remote sensing products

extracted chlorophyll

Is there a better in situ sensor?

Chl a-meter?fluorescence

Roesler, unpubl.

Chlorophyll absorption is a primary ocean color variable.Would 3-wavelength chlorophyll absorption be an

improvement?

What sensors? How to quantify relationships?

2) Toward validation of remote sensing products

extracted chlorophyll

Red peak absorption

Roesler, unpubl.

Figure containing unpublished data was removed

3) Validation of biogeochemical models primary productivity – improved input to models

validate biomass; vertical distribution; real Temp. from ARGO PS coefficients (Cullen – Ek) (not climatologies)

fluorescence particulate backscatter

Vertical distributions Temperature for PP models

Perry, unpub. http://flux.ocean.washington.edu/

Bay of Bengal, 29 April 2009

Net community production – O2 ARGO floats

ARGO floats near Hawaii.Riser & Johnson. 2008. Nature 451: 323

3) Validation of biogeochemical models

Stoichiometric measures of community productionwith well-characterized and calibrated sensors

D’Asaro, Lee, Perry, Fennel – North Atlantic Bloom

every time you look at the ocean in a new way, you learn something new – paraphrased from Russ Davis

4) Discovery

Chl

S

T

Inshore offshore

25 Mar 09

Two types of potential applications for floats & gliders:1) experiment scale – weeks to months to ~ year, mesoscale to basin scale [this scale also part of process to go to next step, below; sensor calibration and characterization critical to ‘getting it right’.]

2) operational scale – bio-ARGO or BGC-ARGO floats (note: existing ARGO Program is considering using gliders as well as floats)

Sensor issues(and there are many)

Multiple sensors for same process

Start where you know the processes: work first with the known –> then move to the unknown.

Better sensors

Etc., etc., etc.

But . . .

The way forward:

IOCCG BIO-Argo WG (Claustre)O2-ARGO (Johnson, Riser, Gruber, Körtzinger)

Ocean Obs 09 White Paper (Perry, Claustre, Testor) OCB scoping workshop on observing BG cycles on

global scates with floats and gliders(Johnson; reports being written)

Proposed standing committees, US and international

Motivation: Reduce uncertainty 1) Validation of remote sensing products2) Validation of biogeochemical models 3) Discovery4) Data even when cloudy