Surface pulses in the lower St. Lawrence Estuary

Abstract

Temperature, salinity, sea level and meteorological data from the ‘couplage entre les processus physiques et biogéochimiques’ (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 the passage of a pulse event, indicated that profound changes occurred in the hydrography at the head of the Laurentian Channel. A factor analysis of rotated eigenmodes of surface temperature and salinity indicated 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 relate salinity and temperature variations to forcing variates. It was found that sea level elevation and local winds accurately predicted fluctuations 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 propagation while temperature fluctuations could not be predicted by any of the forcing variates. © 1998 Taylor & Francis Group, LLC.