Percentage contribution of inputs from the Atlantic, Irish Sea, English Channel and Baltic into the North Sea during 1988: A tracer-based evaluation using artificial radionuclides

Abstract : A sampling cruise carried out in the North Sea in July 1988 has enabled the construction of general maps showing the distribution of salinity and temperature as well as the activities of the radionuclides 125 Sb, 137 Cs and 134 Cs. An inspection of the raw data and the distribution patterns so obtained shows the important role of meteorological fluctuations in the movement of near-surface waters throughout the North Sea. A simple mixing model is used to interpret the North Sea dataset in terms of four contributory water-masses (the Atlantic, Irish Sea, English Channel and Baltic), each of which can be identified by its specific characteristics. Maps are drawn up which indicate the contribution factor in percentage of each of these water masses at all points in the North Sea to a precision better than 15%. Pt is also possible to extract the contribution of direct fallout resulting from the Chernobyl accident; comparison with previously obtained results allows an evaluation of the rate of renewal of surface waters in the North Sea over a period of two years. In all areas, this value appears to be better than 75%.