Open Ocean CDOMOpen Ocean CDOMProduction and FluxProduction and FluxOpen Ocean CDOMOpen Ocean CDOM

Production and FluxProduction and Flux

Norm Nelson, Dave Siegel, Stéphane MaritorenaChantal Swan, Craig Carlson

UC Santa Barbara

Norm Nelson, Dave Siegel, Stéphane MaritorenaChantal Swan, Craig Carlson

UC Santa Barbara

ACE Ocean Productivity and Carbon Cycle (OPCC) Workshop UCSB, June 2011

OutlineOutline

What is CDOM and why should we

care

Remote sensing of CDOM

CDOM Dynamics in the global ocean

What is CDOM and why should we

care

Remote sensing of CDOM

CDOM Dynamics in the global ocean

CDOM What and WhyCDOM What and Why CDOM is dissolved (passes 0.2 m filter) organic matter that

absorbs light.

CDOM has a major impact upon ocean color -- influences retrieval of chlorophyll, penetration of PAR and UV to depth. This enables remote sensing of surface CDOM.

CDOM is produced by all kinds of heterotrophic activity and is destroyed primarily by solar radiation.

CDOM is found in measurable (if you’re careful) quantities at all depths everywhere in the ocean.

CDOM is not correlated to DOC abundance in the open sea.

CDOM is dissolved (passes 0.2 m filter) organic matter that absorbs light.

CDOM has a major impact upon ocean color -- influences retrieval of chlorophyll, penetration of PAR and UV to depth. This enables remote sensing of surface CDOM.

CDOM is produced by all kinds of heterotrophic activity and is destroyed primarily by solar radiation.

CDOM is found in measurable (if you’re careful) quantities at all depths everywhere in the ocean.

CDOM is not correlated to DOC abundance in the open sea.

Zooplankton CDOM Production

0

0.5

1

1.5

2

2.5

3

3.5

4

250 300 350 400 450 500 550 600 650 700

Wavelength (nm)

Ab

sorb

ance

(1/

m)

FSW control

FSW + tow water control

Candacia ethiopica (copepod)

Example spectra for controls vs. plankton

Solar Bleaching of CDOM

daCDOM/dt (measured)E0*ācdom

TimeTime

Chantal Swan, UCSB

CDOM is also an primary sensitizer of photochemical reactions involving climate-relevant trace gases (CO2, CO, OCS, DMS)

CDOM is an indicator of terrestrial runoff and riverine input to the ocean

Alas: In the open ocean we can’t ascribe carbon content to CDOM (yet?) nor do we know much about the identities of the chromophores

CDOM is also an primary sensitizer of photochemical reactions involving climate-relevant trace gases (CO2, CO, OCS, DMS)

CDOM is an indicator of terrestrial runoff and riverine input to the ocean

Alas: In the open ocean we can’t ascribe carbon content to CDOM (yet?) nor do we know much about the identities of the chromophores

CDOM What and Why (2)CDOM What and Why (2)

Photochemical CO production from space

CDOM from Ocean ColorCDOM from Ocean Color

CDOM absorption spectrum is distinct from phytoplankton absorption

Ocean color reflectance spectra can be inverted to retrieve absorption by CDOM and particles and particulate backscattering

CDOM absorption spectrum is distinct from phytoplankton absorption

Ocean color reflectance spectra can be inverted to retrieve absorption by CDOM and particles and particulate backscattering

CDOM Optics and Remote Sensing

CDOM Optics and Remote Sensing

CDOM

Particles

Mean Global Surface CDOM DistributionFrom SeaWiFS as acdm(443 nm, m-1)

Garver-Siegel-Maritorena model

Mean Global Surface CDOM DistributionFrom SeaWiFS as acdm(443 nm, m-1)

Garver-Siegel-Maritorena model

Siegel et al. [2005] JGR -- Nelson et al. [2010] GRL

acd

om (443 nm

, m-1)

Matchup with NOMAD data (IOCCG IOP report; Lee et al. 2006)

Model-data fits are pretty good – though not excellent

GSM01 is optimized for all 3 retrievals (CHL, CDM, BBP)

Matchup with NOMAD data (IOCCG IOP report; Lee et al. 2006)

Model-data fits are pretty good – though not excellent

GSM01 is optimized for all 3 retrievals (CHL, CDM, BBP)

CDOM from Ocean Color

CDOM from Ocean Color

Global Dynamics of CDOMGlobal Dynamics of CDOM

Example CDOM ProfilesExample CDOM Profiles

Atlantic

Pacific

Indian

Atlantic

Pacific

IndianCD

OM

and A

OU

D

istr

ibuti

on

CD

OM

and A

OU

D

istr

ibuti

on

[Nelson et al. 2010]

CDOM / AOU CorrelationCDOM / AOU Correlation

CDOM is produced primarily as a function of remineralization (terrestrial inputs are local, only a few taxa of autotrophs produce CDOM)

CDOM is destroyed primarily by photolysis (we don’t observe labile DOM as it’s consumed too rapidly by microbes)

Time scales for CDOM production / destruction are comparable to time scales for ocean circulation (otherwise the ocean would be yellow)

Observed CDOM distribution results from a balance between source/sink processes and circulation

CDOM is produced primarily as a function of remineralization (terrestrial inputs are local, only a few taxa of autotrophs produce CDOM)

CDOM is destroyed primarily by photolysis (we don’t observe labile DOM as it’s consumed too rapidly by microbes)

Time scales for CDOM production / destruction are comparable to time scales for ocean circulation (otherwise the ocean would be yellow)

Observed CDOM distribution results from a balance between source/sink processes and circulation

CDOM Dynamics SummarizedCDOM Dynamics Summarized

CDOM Dynamics - N. Pacific / IndianCDOM Dynamics - N. Pacific / Indian

N Eq

Weak ventilation in northern basinParticle flux leads to CDOM accumulation

BiologicalPhysicalBleaching

CDOM Dynamics - N/S Atlantic CDOM Dynamics - N/S Atlantic

N or S Eq

Strong ventilation in subarctic basinHigher surface CDOM signal transmitted to deep

BiologicalPhysicalBleaching

CDOM Dynamics - S Pacific/Indian CDOM Dynamics - S Pacific/Indian

S Eq

Strong ventilation in Southern Ocean Lower surface CDOM signal transmitted to deep

BiologicalPhysicalBleaching

CDOM is a remotely sensible semiconservative tracer, produced by heterotrophs and destroyed by photolysis

The relationship between CDOM and oxygen (as AOU) in the deep sea is modulated by circulation processes

CDOM assessment is important to do ocean color right, and is useful in its own right

CDOM is a remotely sensible semiconservative tracer, produced by heterotrophs and destroyed by photolysis

The relationship between CDOM and oxygen (as AOU) in the deep sea is modulated by circulation processes

CDOM assessment is important to do ocean color right, and is useful in its own right

Summary / ConclusionsSummary / Conclusions

Extra slidesExtra slides

Remote sensing reflectance spectrum can be inverted to retrieve inherent optical properties (absorption and backscattering spectra) of the surface water (mixed layer to ~ 60m).

Absorption spectra can be deconvolved into particle absorption and CDOM+detritus absorption spectra (which we call CDM) given some assumptions about the shape of the component spectra.

Garver-Siegel-Maritorena model (GSM) uses shape functions determined using a global optimization of available global open ocean field data.

Remote sensing reflectance spectrum can be inverted to retrieve inherent optical properties (absorption and backscattering spectra) of the surface water (mixed layer to ~ 60m).

Absorption spectra can be deconvolved into particle absorption and CDOM+detritus absorption spectra (which we call CDM) given some assumptions about the shape of the component spectra.

Garver-Siegel-Maritorena model (GSM) uses shape functions determined using a global optimization of available global open ocean field data.

CDOM Optics and Remote Sensing

CDOM Optics and Remote Sensing

Seasonal CDOM Cycle

Seasonal CDOM Cycle

Seasonal changes at most latitudes

Lower in summer

Reduced in tropics

Higher towards poles

Hemispheric asymmetry

Seasonal changes at most latitudes

Lower in summer

Reduced in tropics

Higher towards poles

Hemispheric asymmetry

%CDM

CDM

Surface CDOM & SeaWiFS

Surface CDOM & SeaWiFS

A16N

A20

A22

r2 = 0.65; N = 111slope = 1.16

Siegel et al. [2005] JGR

a*cdom(325)a*cdom(325)

aa**cdom cdom = CDOM / DOC= CDOM / DOC

(units m(units m22gg-1-1))

Upper layers bleaching Upper layers bleaching & production signals& production signals

aa**cdomcdom increases w/ increases w/

depth & agedepth & age

CDOM “abundance” CDOM “abundance” changes less than the changes less than the DOC decline -- CDOM is DOC decline -- CDOM is refractory DOMrefractory DOM

Aging

NewNew

Ble

ach

ing

Nelson et al. [2007] DSR-I

Regressions between age and CDOM

Regressions between age and CDOM P < 0.025 P < 0.025

P < 0.025

P < 0.025

T ~ 10y

T ~ 50y

T > 200 y

Nel

son

et a

l. [2

007]

DS

R-I

Trends in CDOM spectral characteristics - N. Atl.

Trends in CDOM spectral characteristics - N. Atl.

P < 0.025P < 0.025 P < 0.025

P < 0.025P < 0.025

P < 0.025 P < 0.025

Nel

son

et a

l. [2

007]

DS

R-I