This work formed part of a multi disciplinary research programme conducted 25 km offshore of Kuujjuarapik in southeastern Hudson Bay (Canadian Arctic). Large differences in salinity and nutrient concentration between brine, ice and under-ice surface water were used to study the different phases observed during the period of melt initiation. We present a discussion of processes governing the flushing of brine and the development of a melt layer below first-year sea ice. Phosphate, nitrate + nitrite and silicic acid distributions within the first 30 cm below the ice are described. Three distinct steps were observed during the melt initiation: a phase of brine rejection; a phase of flushing associated with the development of a buoyant melt layer rich in nutrients; and a phase of melt of the ice-water interface characterized by the development of a melt layer poor in nutrients. The flux of brine during the four days of brine flushing was estimated at 0,009 m(3)/day/m(2) (i.e. equivalent to a melt rate of 9 mm/day). Our findings confirm that exchanges between the water column and the sea-ice sheet are dominated by tidal current fluctuations. The increase of current velocities provoked the pumping of a fraction of the bottom-ice brine content and a dissipation of vertical structures. Low tidal velocity periods created conditions suitable for the development of a melt layer.