TITLE:    Bio-optical properties of Antarctic coastal waters
AUTHORS:  Heidi Dierssen, Raymond C. Smith, Karen S. Baker
DATE:     9-13 November 1998
PLACE:    Kona, Hawaii

SPIE14 The International Society for Optical Engineering
LTER Contribution #169

Abstract

In Antarctic coastal waters, primary production is tightly coupled to 
chlorophyll concentrations. However, retrieval of chlorophyll concentrations 
from remotely sensed reflectance measurements using standard algorithms may 
not be accurate for Southern Ocean waters. The relationship between 
water-leaving radiance and pigment concentrations has been found to be 
significantly different in the Southern Ocean compared to other oceanic 
regions. Here we evaluate a large bio-optical dataset (>1000 samples)
collected in Antarctic Peninsula waters in conjunction with the LTER program.
The remotely sensed reflectance spectrum appears significantly different for
increasing chlorophyll concentrations when compared to the global SeaBAM
dataset. The Antarctic reflectance is significantly lower in the green region
of the spectrum for high chlorophyll concentrations (>1 mg Chl m-3) and no
spectral hinge point is apparent. Because the reflectance in the green is lower,
applying the general processing algorithms for both CZCS and SeaWiFS in these
Antarctic waters results in underestimates of chlorophyll by roughly a factor
of two. Using a radiative transfer model, we show that the shape of the 
Antarctic remote sensing reflectance spectra is consistent with waters that
have very low backscattering, even in high chlorophyll situations. Low 
coefficients of backscattering could arise because concentrations of bacteria
and viruses, the primary backscattering particulates, have been found to be an
order of magnitude lower throughout the Southern Ocean when compared to most
other oceanic regions.