SURFACE PULSES IN THE LOWER ST.-LAWRENCE ESTUARY

Temperature, salinity, sea level and meteorological data from the 'cou plage entre les processus physiques et biogeochimiques' (COUPPB) study of 1990 were examined to determine the forcing of fresh water pulses in the lower St. Lawrence Estuary. Anchor stations, during and after t he passage of a poise event, indicated that profound changes occurred in the hydrography at the head of the Laurentian Channel. A factor ana lysis of rotated eigenmodes of surface temperature and salinity indica ted three co-varying groups the first, on the north shore of the river the second on the south slope of the Laurentian Channel and the third in the middle of the estuary A multivariate regression was used to re late salinity and temperature variations to forcing variates. It was f ound that sea level elevation and local winds accurately predicted flu ctuations on the north shore. Salinity and temperature fluctuations on the south shore were best explained by propagation. In the middle of the estuary, salinity fluctuations were only weakly explained by propa gation while temperature fluctuations could not be predicted by any of the forcing variates.