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

A sampling cruise carried out in the North Sea in July 1988 has enable d the construction of general maps showing the distribution of salinit y and temperature as well as the activities of the radionuclides Sb-12 5, Cs-137 and Cs-134. An inspection of the raw data and the distributi on patterns so obtained shows the important role of meteorological flu ctuations 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, E nglish Channel and Baltic), each of which can be identified by its spe cific characteristics. Maps are drawn up which indicate the contributi on factor in percentage of each of these water masses at all points in the North Sea to a precision better than 15%. It is also possible to extract the contribution of direct fallout resulting from the Chernoby l accident; comparison with previously obtained results allows an eval uation 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 t han 75%.