Jeudi 24 mars - Investigation of sulphur plumes along the Namibian coast using remote sensing methods
Mar 24, 2016
from 11:00 AM to 12:00 PM
Thomas Ohde, Leibniz Institute for Baltic Sea Research (IOW), Germany
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Leibniz Institute for Baltic Sea Research (IOW)
Title : Investigation of sulphur plumes along the Namibian coast using remote sensing methods
The presentation is focused on the study of sulphur plumes in the Namibian coastal area of the Benguela upwelling system. An overview is given about the current scientific knowledge. These events, which are not found anywhere else in the world ocean with such intensity, influence the Namibian ecosystem, the local fishing industry and the aquaculture farming, a rapidly growing industrial sector, as well as the tourism because of their toxic properties. Conventional observations were made by local observers, recording milky turquoise discoloration of surface water, typical smell, and toxic effect on marine organisms. In-situ measurements on the basis of water samples allow only the investigation of very local events. Up to now, their spatial and temporal occurrence at the Namibian coast can be observed only by ocean colour remote sensing by their characteristic milky turquoise-coloured patches.
The method for the registration and identification of colloidal sulphur in the surface water layer based on high spectral resolution data of the ESA ocean colour sensor MERIS (Medium Resolution Imaging Spectrometer) is presented. Other discoloured events like algae blooms and sediment loaded waters of river outflows or coastal resuspension are differentiated from sulphur plumes by their spectral characteristics. Based on the different derived optical properties a classification algorithm was developed and applied for the detection of onshore sulphur plumes. Results are presented on the location, size, frequency and intensity of sulphur plumes in the Benguela upwelling system in relation with the physical and biogeochemical conditions.