First data of Uranium-236 in the North Sea

Abstract In this paper we present the first 236 U-measurements from North Sea water samples. The measurements are performed within an ongoing project that intends to map the distribution of 236 U in the Atlantic Ocean and thus to explore the potential of 236 U as a new oceanic tracer. We describe the latest modifications of the low energy ETH AMS system TANDY that allow determining the concentrations of both 238 U and 236 U and the 236 U/ 238 U ratio during only one AMS measurement. Further, we present our chemical preparation procedure and, finally, the first 236 U data from the North Sea is discussed in detail. A simple conceptual model is used to simulate the temporal evolution of the 236 U-concentration in the North Sea. The simulated water mass residence time is in good agreement with independent oceanographic data. Based on these initial results we conclude that anthropogenic 236 U has a large potential as a new transient and extremely conservative tracer in Oceanography.