Klaus Ricklefs

Solar Driven Geomagnetic Anomalies and Sperm Whale (Physeter macrocephalus) Strandings Around the North Sea: An Analysis of Long Term Datasets

To stimulate the discussion about possible reasons for whale strandings, we suggest solar driven geomagnetic variations as one further explanation for this phenomenon. Following this hypothesis that whales may strand due to geomagnetic disturbances we compared annual means of stranding event numbers of sperm whales (Physeter macrocephalus) along the North Sea coasts with yearly averaged numbers of geomagnetic anomaly intensities (aa- indices). Based on a Generalised Additive Model technique, our new approach suggests that over the last 400 years 20% of the stranding events can be correlated with aa-index variabilities. Furthermore, the increased stranding numbers of the last decades could be explained by the exceptional intensive disturbances of the earths magnetic field in the same period.

Sediments and suspended matter in the sylt-Rømø tidal area: A summary of Results Collected in the “SWAP”-project

The Sylt-Rømø tidal basin has evolved during the last 5000 to 5500 years. In 1992 it covered 401.4 km2, of which 60% were subtidal areas and 40% were intertidal flats. With the beginning of the last century reliable maps became available for this part of the Wadden Sea. Since that time significant losses of sediment in subtidal areas can be demonstrated.The main part (114.7 km2, 72%) of the intertidal flats is built up of sand. Sandy deposits also prevail in the subtidal areas. Muddy sands with 10 to 50% silt and clay form a nearshore, more or less narrow belt along the islands, dams and main land coasts. They cover 39 km2 or 25% of the intertidal region. Muddy intertidal flats and salt marshes enclose less than 10 km2 each. This sediment distribution pattern exhibits the typical zoning of tile deposits in an intertidal bay. The spatial distribution of the fine-grained suspended sediments largely follows this pattern. In the Sylt-Rømø tidal area the net accumulation rate of these sediments of about 58000 t/a is relatively low.KurzfassungDas Lister Tidebecken entstand in den letzten 5000 bis 5500 Jahren. Es umfaßte 1992 insgesamt 401,4 km2, davon 60% subtidale und 40% tidale Flächen. Für die Zeit ab etwa 1800 liegen zuverlässige Karten vor. Seit diesem Zeitpunkt sind starke Materialverluste im Subtidal nachweisbar.Der größte Teil (114,7 km2, 72%) der intertidalen Wattflächen ist aus Sand aufgebaut. Sandige Ablagerungen herrschen auch in den subtidalen Bereichen vor. Schlicksande mit 10–50% Silt und Ton bilden ein küstenahes, mehr oder weniger schmales Band entlang der Inseln und Dämme sowie vor der Festlandsküste.Sie bedecken 39 km2 oder 25% der Wattflächen. Schlickwatten und Salzwiesen umfassen jeweils weniger als 10 km2.Dieses Sedimentverteilungsmuster gibt die typische Zonierung einer Bucht des Gezeitenbereiches wieder. Die räumliche Verteilung der supendierten, feinkörnigen Sedimente folgt im wesentlichen diesem Muster. Die Ablagerungsrate derartiger Sedimente im Sylt-Rømø Wattenmeer ist mit 58000 t/a vergleichsweise gering.

Echo sounding on suspended particulate matter in the elbe estuary

Assessment of suspended particulate matter (SPM) in an estuary, and its transport by tidal currents, is a difficult task in spite of the existence of verifiable current models. The first encouraging results from echo soundings are presented.