#9 Topic: Ocean Color Remote Sensing
Lecturer: Astrid Bracher
Date: Monday, March 1, 2020 10:00 – 11:00 a.m.
Light plays an important role in aquatic ecosystems. Penetration of light underwater influences various biogeochemical processes and also influences activities and behavioral patterns of marine organisms. In addition, dissolved and particulate water constituents present in the water column absorb and scatter light, giving water its characteristic color. The concentration or abundance of these constituents, referred to as optically active constituents (OACs) also determine light availability underwater. Thus color being an indicator of water column content, serves as a water quality parameter. Monitoring of the ocean color variables, such as the OAC concentrations and their optical properties, therefore, allows assessment of the health of an ecosystem. Over the past 25 years, ocean color remote sensing has revolutionized our understanding of marine ecosystems and biogeochemical processes by providing continuous global estimates of various important biogeochemical parameters by detecting the spectral variations in the water-leaving radiance (or reflectance), which is the sunlight backscattered out of the ocean after interaction with water and its constituents. In the open ocean the signal is primarily dependent on phytoplankton which contain photosynthetic pigments, primarily chlorophyll-a (chl-a) and an assemblage of other pigments, and which coexist together with associated detrital and colored dissolved organic matter (CDOM) that are related to the phytoplankton. Coastal waters are more complex optically on account of the additional influences of re-suspended particulates, or river run-off which could contain terrestrial suspended particulates or CDOM which are independent of the phytoplankton assemblage. Within this lecture the basic concepts of ocean optics and of processing satellite data to remove atmospheric effects and retrieve ocean color products introduced, some examples of application of products by exploiting feedback processes of OACs to ocean physics and atmosphere are shown and links to publicly available satellite products are provided.