PARTICULATE ORGANIC CARBON, LIGHT SCATTERING AND OCEAN COLOR Dariusz Stramski

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PARTICULATE ORGANIC CARBON,LIGHT SCATTERING
AND OCEAN COLORDariusz Stramski
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OBJECTIVES

• Develop an understanding of variability in the
  relationships between particulate organic carbon
  (POC), light scattering, and ocean color
• Develop algorithms for estimating POC from
  optical measurements

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BACKGROUND reflectance Rrs , backscattering bp
, and POC

• Rrs bb / a
• bb POC because
• bulk bb is related to particle size-refractive
  index distributions F(D,n)
• single particle organic carbon is related to
  particle size (D) and refractive index (n)
• Therefore Rrs ? bb ? POC

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Rrs ? bb bbp ? POC
EXAMPLE DATA FROM THE ROSS SEA AND ANTARCTIC
POLAR FRONT ZONE
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In situ measurements on the BIOSOPE cruise

• Vertical profiling with Multisensor Datalogger
  System that includes
• Hydroscat-6 (HobiLabs) 442, 470, 555, 589,
  620, and 671 nm
• two a-Betas (HobiLabs) 420 and 510 nm
• two C-Stars (WetLabs) 488 and 660 nm
• fluorometer WetStar (WetLabs)
• PAR sensor (Biospherical)
• CTD sensors (Seabird)
• The system is autonomous in the sense that all
  the sensors have internal power supply and data
  storage. The instruments can be deployed using
  any ships winch (there are no special
  requirements for the winch cable). If separate
  deployments are impossible then, as a minimum, it
  would be desirable to integrate Hydroscat-6 and
  two a-Betas with ships rosette or other in situ
  package to ensure that we have multispectral
  backscattering capability covering a broad
  spectral range.

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Measurements on discrete water samples

• Volume scattering function (l 532 nm, 18 angles
  between 15o and 165o) with Dawn EOS (Wyatt Tech).
• Because of limited experience, these
  measurements will have largely an exploratory
  character. The protocol will likely include the
  measurements on untreated and acid-treated
  samples to separate the contribution of PIC to
  light scatter. Relatively small volumes of water
  (tens to hundreds of mL) will be required.
  These measurements will be made at selected
  stations and limited number of depths.
• Elemental and mineralogical analyses of
  particulate matter with mass spectroscopy and
  X-ray techniques.
• Water samples (0.5 3 L) will be filtered and
  the sample filters will be stored for post-cruise
  analyses. These samples will be taken in
  parallel to samples for light scattering
  measurements. If water availability is
  problematic, then the dry weight filters could
  possibly be used after measuring the dry weight
  of particles.