Doctor of Philosophy (PhD)
Oceanography and Coastal Sciences
In recent decades the Bering Sea has been subjected to large climatic variability with cascading consequences on its productive marine ecosystem. Long-term as well as short-term monitoring is essential if we are to maintain its capability to supply the resources on which the national and local economy depend. Remote sensing together with in-situ and laboratory measurements of physical, biological and optical properties have considerable potential for monitoring and measuring the effects of climate-driven changes on this ecosystem. A major shortcoming to obtain accurate estimates of optically active components (such as colored dissolved organic matter, non-algal particulate matter, and phytoplankton) from ocean color remote sensors has been the lack of in-situ bio-optical data in the Bering Sea. To address this issue, the central part of this dissertation was to i) assess phytoplankton absorption of culture and seawater samples using spectrophotometric and pigment reconstruction methods and ii) obtain a suite of in-water measurements for characterization and parameterization of light absorption properties in the southeastern Bering Sea. One of the main objectives was to assess the bio-optical models and parameterizations currently used in satellite algorithms for the southeastern Bering Sea, which were found to be inapplicable in these waters due to the dominant contribution by CDOM absorption. The CDOM absorption accounted for greater than 50% of the diffuse light attenuation coefficient and caused the remote sensing reflectance to be lower, more in the blue than the green region of the visible spectrum, causing the blue to green reflectance ratios to decrease by a factor of ~2. The lower specific absorption relative to lower and middle latitudes indicated significant pigment packaging and/or change in pigment composition which was consistent with variability in phytoplankton community structure. These results suggested the need for developing regional algorithms and parameterizations; regional empirical algorithms were developed using relationships between remotely sensed reflectances and properties of optically active components in the study region. The results from this dissertation will enhance our ability to achieve greater accuracy in deriving remotely measured optical parameters of sub-arctic regions required for an improved understanding of biological responses to climatic forcing.
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Naik, Puneeta Suresh, "Oceanic Light Absorption Properties: Assessment and Characterization in the Southeastern Bering Sea Using Field and Satellite Observations" (2011). LSU Doctoral Dissertations. 768.