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Ocean color remote sensing of chlorophyll and primary production west of the Antarctic Peninsula
Dierssen, H.M. (2000). Ocean color remote sensing of chlorophyll and primary production west of the Antarctic Peninsula. PhD Thesis. University of California: Santa Barbara. ISBN 9780493126685. 161 pp.
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| Abstract |
This dissertation addresses two fundamental questions. First, how do biomass and primary production in Antarctic coastal waters compare to temperate waters? Second, how can we use satellite ocean color observations to accurately estimate biomass and primary production in these Antarctic waters? Satellite technology is critical for understanding the large scale patterns of biomass and primary production in the remote waters of the Southern Ocean. However, considerable uncertainty exists in satellite-derived estimates of biomass and production for this region. As discovered in this dissertation, unique regional algorithms are required for estimating both biomass and primary production in Antarctic waters. Data collected in conjuction with the Palmer Long Term Ecological Research project along the western Antarctic Peninsula are used to address these questions. From analysis of bio-optical parameters measured at over 1000 stations, the relationship between remotely sensed reflectance and biomass (evaluated as chlorophyll concentrations) is found to be significantly different from other oceanic regions. Remote sensing reflectance is higher in the blue and lower in the green region of the visible spectrum. This is hypothesized to be due to a combination of low backscattering and low absorption per unit chlorophyll. A new empirical algorithm is developed to predict chlorophyll from remotely sensed radiance. If chlorophyll concentrations are accurately retrieved from a satellite, then over 60% of the variability in primary production can be explained. Taking into account the relatively uniform chlorophyll-normalized production profile and low maximum chlorophyll-normalized production (P Bopt) characteristic of these cold well-mixed Antarctic waters, an optimized depth-integrated primary production is presented that explains over 70% of the PAL/LTER data and historic data collected from the region. Finally, the chlorophyll and primary production models are applied to monthly satellite data obtained from the Sea-viewing Wide Field of View Sensor (SeaWiFS). We find that, as predicted, SeaWiFS generally underestimates chlorophyll concentrations and follows our algorithm. Using the satellite-derived chlorophyll, we are able to model PP both monthly and annually for waters near Palmer Station and for the entire Southern Ocean. Interannual variability is highest in coastal waters near Palmer Station (7-fold variability) and in regional ice shelves containing large polynyas. |
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