Sediment transport, resuspension and accumulation rates in the northeastern Skagerrak

Abstract

Results of watercolumn light transmission measurements in the Skagerrak and of 210Pb excess and 137Cs determinations in boxcore sediments of the eastern Skagerrak are combined to study regional sediment transport, resuspension and sedimentation patterns and rates. In the upper water layer a 20 m thick surface nepheloid layer formed by concentration of particles at the thermocline and pycnocline is best developed in the eastern Skagerrak and less well in the southwestern Skagerrak off the Danish Coast. Bottom nepheloid layers are extensively developed in the southeastern Skagerrak and indicate additional sediment input via resuspension in shallow water areas and near bottom sediment transport in suspension following the prevailing current regime. Locally the transmission in the BNL is reduced by more than 50%, compared to clear water transmission values between 85 and 90%. 210Pb and 137Cs derived sedimentation rates are highest in the eastern and northeastern Skagerrak, and least in the central deep basin. There is generally a good agreement between 137Cs and 210Pb data, indicating that sediment accumulation on the short (∼ 30 year) and longer (∼ 100 year) time scale is of comparable magnitude.