Laney-Letelier-Abbott 2005 CoRP CalVal Symposium, CIOSS COAS OSU Ocean Color Products: The challenge...

Laney-Letelier-Abbott 2005 CoRP CalVal Symposium, CIOSS COAS OSU

Ocean Color Products:The challenge of going from stocks to

ratesSam LaneyRicardo Letelier

Mark Abbott

NOAA/NESDIS CoRP Satellite Calibration & Validation Symposium

July 13-14 2005

Cooperative Institute for Oceanographic Satellite Studies

College of Oceanic & Atmospheric SciencesOregon State University, Corvallis OR


Overview:

• How ocean phytoplankton standing stocks relate to

primary productivity in the ocean

• Current remote sensing approach for estimating

marine primary productivity, & some concerns with it

• How remote sensing of chlorophyll fluorescence is

providing insight into photosynthetic variability that

affects estimates of primary production


Stocks (or pools):

• Biomass, abundance

“standing stock”

Good at measuring stocks

of phytoplankton with

remote sensors:

SeaWiFS “chlorophyll”

#1 scientific use of ocean

color remote sensing

data: phytoplankton chl

Rates (or flux):

• Flow of energy or matter

through a stock

“primary production”

“sustainable yield”

“carbon sequestration”

Important issues in marine

ecology, but…

Not nearly so easy to

assess using remote

sensing


Challenges of aquatic photosynthesis:

(compared to remote sensing terrestrial production)

Optical:

• Need large dynamic range from a weak signal

Physiological:

• C uptake rates ~ 10x standing stock (0.2x for

land)

• Considerable spatiotemporal variability in

stocks

• Phytoplankton very different photosynthetically

• Chl not major absorbing pigment in some

phytoplankton

• Wide physiological range of carbon:chl (factor of 10)


Top of the Atmosphere Radiances (Lsat)

Radiative Transfer Models

Normalized Water Leaving Radiances (nLw)

Primary Production model

Higher level model (e.g. export production,

carbon sequestration, fisheries)

Photosynthetic Available

Radiation (PAR) = 400-700 nm

Ocean Chlorophyll Algorithms (empirical or

semi-analytical)

Sea surface Chl a concentrations

Photosynthetic efficiency (P)

(derived empirically from

SST)

Image: NASA

Image: OPP IMCS Rutgers


F = PAR ([chl] a*) F

PriProd = PAR ([chl] a*) P

So, P - F are

inversely related:

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

400 450 500 550 600 650 700

Wavelength, nm

Lu/E

s

Phytoplankton absorption = [chl] a*

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

400 450 500 550 600 650 700

Wavelength, nm

Lu/E

s

Phytoplankton fluorescence

by chl

Chl fluorescence, photosynthesis, & production:

PAR (sunlight)

Absorbed Radiation by Phytoplankton (ARP PAR chl

a*)

PhotosynthesisP

Fluorescence F

Ricardo Letelier

until 5 years ago, all effort on blue-green region, because best place to look at absorption = chl. gives estimate of light abs by phytos. however, in red wavelengths PS is emitting light. We can now measure this from space using fluroescence channels. reason why this is useful...


Fluorescence Line Height (FLH)

Sea surface upwelling irradiance (calculated @ 10 mg Chl m-3 )

Chl fluorescence can be measured by

modern remote sensors, e.g. MODIS or

MERIS

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

600 620 640 660 680 700 720 740 760

FLH

Lu1

Lu2

Lu683

Wavelength, nm

Exit

ance

, W

m-2

µm

-1

FLH = Lu683 – Baseline683

Baseline683 = Lu1 - [(Lu1-Lu2)/(lLu2-lLu1)]*(683-lLu1)


FLH validation:

Open ocean: - HOT cruises - Southern Ocean - MOBY mooring

Coastal: - GLOBEC - COAST

http://www.satlantic.com/cgi-bin/nph-null


In situ vs. remotely sensed FLH:Oregon coastal region

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0 0.05 0.1 0.15 0.2 0.25

Oregon Drifters FLH, W m-2 m-1 sr-1

MO

DIS

Terr

a F

LH,

W m

-2

m-1 s

r-1

1:1


From Hoge et al.

Validating MODIS Fluorescence:Line ‘A’

Line ‘B’

Frontal regions

http://aol.wff.nasa.gov/jpegs/twinotter.jpg


Images: ocean at mesoscales, a decoupling between FLH &

chl

chl

FLH

Differences in?

• species composition

• environmental forcing


Chl FLH

Observe changes in FLH/chl during the day:

nearshore, frontal, and pelagic regions

C

B

A

A = offshore

B = frontal regionsC = nearshore


Can associate variability in FLH/PAR with photosynthetic differences

resulting from nutrient availability

PAR irradiance (mol quanta m-2 s-1)

FLH / PAR

FLH

Nitrate-limited Nitrate-starved


FLH: status & future directions

• Field validation efforts suggest that FLH is a robust remote sensing product

• Lab validation shows that FLH helps to identify & quantify key physiological aspects of photosynthesis & production

• To improve remote sensing PP with FLH, need to know its diurnal dynamics. Chl fluorescence from geosynchronous sensor (HES-CW on GOES-R)?


Rate of calcification

Rate of N2 fixation Silicate flux

Ocean color other important rates :

e.g. Balch group

e.g. Subramaniam group, Westberry

e.g. Platt group

Ricardo Letelier

at end; may notbe only way to look at ecosystem structure in environmetn. because we knkow structure affected by phyiscs. may also look at pys focirng using remote senting:


Acknowledgments:

• Jasmine Nahorniak & Curt Vandetta (OSU MODIS Direct Broadcast Station)

• NOAA/NESDIS funding through CIOSS• Dennis Clark (NOAA)• Wayne Esaias, Frank Hoge (NASA)


Sea Surface Temperature Chl a Chl Fluorescence Line Height (°C) (mg m-3) (W m-2 m-1 sr-1)

Variability in patterns of chl and FLH

MODIS Terra L2 1 km resolution scene (October 3rd 2001) – COAS/OSU Direct Broadcast


chlFLH empirical(this study)

chlFLH semi-analytical(Huot & Cullen

assuming f = 0.006)

In situ chl

GLOBEC NEP AUGUST 2002

-Both FLH derived chl algorithms appear to slightly overestimate chl a fields.-They do not seem to reproduce the low values observed in situ.-Some of the differences between in situ and FLH derived could be due to time differences and sampling depth (in situ = 5 m depth)


Relevance: • Aquatic photosynthesis affects global fluxes of C, N, O, & other bioelements

• Response to climate change, ecosystem carrying capacities (e.g. fisheries), depend both on stocks & rates

• Phytoplankton standing stocks and primary production correlate only on very large time & space scales

Laney-Letelier-Abbott 2005 CoRP CalVal Symposium, CIOSS COAS OSU Ocean Color Products: The challenge...

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