Light absorption and scattering by ocean waters in the vicinity of the Chatham Rise, South Pacific Ocean

Abstract

Inherent optical properties, namely spectral absorption coefficients of soluble and filterable (Millipore 0.22 µm) particulate constituents, and beam attenuation coefficients, have been measured at 19 stations east of New Zealand, in the vicinity of the Chatham Rise. In-water spectroradiometer irradiance measurements were used to test a recent algorithm for the estimation of spectral absorption coefficients. The results suggest that the algorithm worked from the near-UV through the blue and green parts of the spectrum up to wavelengths at which Raman emission became significant (>590 nm). Comparison with spectroradiometrically derived absorption suggests that calculations of absorption spectra from spectrophotometer measurements of yellow substance and particulate matter captured on filters are biased by use of a published empirical relationship for the ‘path amplification’ factor. However, scattering coefficients obtained from the spectroradiometer data by using the algorithm were in reasonable agreement with those obtained from transmissometry and spectrophotometric data.