Vol. 9, No. 1, 1-12, 2010

Tracing Wadden Sea water masses with an inverse bio-optical and endmember model
Annelies Hommersom, Steef Peters, Hendrik Jan van der Woerd, Marieke A. Eleveld, Marcel Wernand, and Jacob de Boer

With its 500 km length the Wadden Sea is the largest mudflat area in the world. Discharges from various rivers mix here with water from the North Sea. Due to surfacing tidal flats during low tide, the variation in source water, resuspension and extremely high concentrations of Chlorophyll-a (Chl-a), Suspended Particulate Matter (SPM), and Coloured Dissolved Organic Matter (CDOM), large temporal and spatial differences in watercolour can be seen.

To visualise the horizontal mixing of water masses with different colours from MERIS data, two approaches were followed. The first approach was an inverse bio-optical model called HYDROPT, in which the absorption and scattering properties of the water constituents (Specific Inherent Optical Properties or SIOPs) can be adapted to regional values. This approach can be used to determine ‘water types’: water masses in which the SIOPs of the constituents are similar. The second approach was an endmember model, based on spectral reflectance shapes. This approach can be used to determine ‘water classes’: water types in which certain constituents are predominant. The predicted water types and water classes were compared with knowledge on (tidal) distributions of water types in the Wadden Sea.

In the data of March '07 (winter) and May '06 (summer) differences in water types between the North Sea, the Wadden Sea and water originating from the large rivers were seen in the German Bight. The endmember approach was able to visualise mixing between water classes. Results of this method showed dominance by SPM in winter and much higher concentrations of Chl-a and CDOM in summer. A combination of the two methods would probably lead to the best tracing of water masses.

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Submitted: 1 Oct 2009
Revised: 10 Jan 2010
Accepted: 25 Jan 2010
Published: 28 Feb 2010
Responsible editor: Rainer Reuter

Hommersom A, S Peters, H J van der Woerd, M A Eleveld, M Wernand & J de Boer, 2010. Tracing Wadden Sea water masses with an inverse bio-optical and endmember model. EARSeL eProceedings, 9(1): 1-12


EARSeL European Association of Remote Sensing Laboratories, Strasbourg, France


BIS Library and Information System, Carl von Ossietzky University of Oldenburg


ISSN 1729-3782