North Atlantic

Electrical conductivity of the water column; Vertical velocity of the water column (currents); Salinity of the water column; Horizontal velocity of the water column (currents); Temperature of the water column; Concentration of inorganic sulphur species in the water column

Current meters; discrete water samplers; CTD

The North Atlantic Tracer Release Experiment (NATRE) is a study of vertical and horizontal mixing processes in the thermocline region of the sub- tropical gyre of the North Atlantic, with the aim of characterising rates of diapycnal and isopycnal mixing and the processes which give rise to them. The experiment was initiated by the WHOI vessel RV Oceanus and a cruise concurrent with RRS Charles Darwin 68; between 0100h 5 May 1992 and 0700h 13 May 1992, Oceanus released a total of 945 moles of sulphur hexafluoride (SF6) in a series of 9 streaks on an isopycnal surface at approximately 300m. The streaks were 5-10km long, and were injected into a region of order 20x20km centred on 25° 38'N, 28° 15'W. Along with the tracer, 10 SOFAR 'bobber' neutrally buoyant floats were released together with 8 RAFOS floats. The plan for the experiment as a whole is to follow the dispersal of this tracer over a period of a year following release. The spread of the tracer in the vertical will give a direct measure of diapycnal mixing, while the horizontal dispersion of the floats and the tracer will enable the quantification of the isopycnal mixing. The floats serve the additional purpose of indicating the location of the tracer. In order to study the processes driving vertical mixing, measurements of fine structure have been and will be made by RV Oceanus and the Canadian vessel CSS Hudson in the area of the tracer patch. The overall plan for the experiment is: April 1992 Site survey RV Oceanus May 1992 Injection RV Oceanus May 1992 First sampling RRS Charles Darwin October 1992 Second sampling RV Oceanus March 1993 Microstructure CSS Hudson April 1993 Final sampling RRS Charles Darwin This data set comprises the data collected on RRS Charles Darwin 68.

Plymouth Marine Laboratory
Prospect Place The Hoe
Plymouth
England
PL1 3DH
United Kingdom