Jean-Marie M. Dubois

Seasonal Quantification of Coastal Processes and Cliff Erosion on Fine Sediment Shorelines in a Cold Temperate Climate, North Shore of the St. Lawrence Maritime Estuary, Québec

Abstract A quantification of coastal erosion processes on a clay cliff in a cold temperate region was conducted. This study was based on a network of markers that were measured on a monthly basis from 1998 to 2003. During that period, the average retreat rate of the cliff was 1.5 m/y. Our results demonstrate that weathering is a more significant cliff retreat factor than hydrodynamic processes on fine sediment shorelines. This statement opposes conventional understanding. In fact, 65% of the annual cliff retreat took place through the winter season when the waves could not reach the foot of the cliff because of an ice foot. This erosion is caused by cryogenic processes in winter, particularly through freeze–thaw cycles, whereas desiccation and wave undercutting contributed respectively for 20% and 15% of the total annual retreat. The field measurements conducted before and after major storms, especially on October 29, 2000, illustrated that wave undercutting was negligible for the clay cliff. These results do not corroborate with previous studies showing that cliff erosion is mostly controlled by wave undercutting with negligible winter erosion. In a context of global warming, the intensity of cryogenic processes can become more important due to milder winters, an increase in the number of freeze–thaw cycles, and the reduction of the ice foot and snow cover (especially on south-facing cliffs directly exposed to solar radiation). This study demonstrates that the evaluation of sensitivity of coastal systems to climatic change should not be done just for sea-level rise and increased storminess, but also for other climatic parameters. Future research should also take into account approaches combining the studies of marine and terrestrial erosion processes.

Characteristics of late-glacial ice-dammed lakes reconstructed in the Appalachians of southern Québec

Abstract During deglaciation, several valleys of the Appalachians of southern Quebec were affected by the pounding of ice-dammed lakes. More than 300 water planes were reconstructed in the southeastern part of the region with the methodology presented elsewhere in this volume (Quat. Int. (2002) this volume). Their characteristics during deglaciation gradually changed, following four main steps: (1) ice-dammed ponds; (2) ice-dammed lakelets; (3) intermediate lakes; and (4) large ice-dammed lake. These various lake types differed by the size, the shape, the position of the spillway and the depth of the former ice-dammed lake as well as by the relative duration and by the stability degree of each lake level. In this study, a relative duration of each reconstructed lake level was determined using the distance covered by the retreating ice margin during the former existence of the water body. The stability of the water level also explained the difference in the degree of development of shoreline features among water bodies with relatively similar sizes.

Does AVHRR-sea surface temperature fronts in the Beaufort Sea reveal biological hotspots?

Eleven years of NOAA (AVHRR) images of sea surface temperature (SST) have been used to detect ocean thermal fronts in the southeastern Beaufort Sea. As expected, front detection is easier in the summer season. Location of major known fronts (Shelf Break Front, Mackenzie River Plume Front) was confirmed and new frontal regions (Cape Bathurst, Mackenzie Trough, Amundsen Gulf coastal zones) were identified. These fronts appear mostly driven by wind and tidal mixing along steep shelf slopes and may be playing an important role in the biological processes.

A methodology to reconstruct small and short-lived ice-dammed lakes in the Appalachians of Southern Québec

Abstract Previous studies on the deglaciation of the Appalachians of southern Quebec reconstructed only the most extensive ice-dammed lakes and the most stable glaciolacustrine water levels. They only used the best developed shoreline features, and thus were not able to reconstruct small or short-lived ice-dammed lakes, both being characterized by a weak development of their features. We propose a methodology to reconstruct glacial lakes which follows three main steps: (1) the mapping of shoreline features, generally the best developed ones, as in previous studies; (2) the delineation of the former shoreline for each water level, by also considering the less well-developed shoreline features which were found during field surveys designed as a function of the presumed shoreline position; and (3) the mapping of the maximum extension of the water plane, which includes the location of the former ice dam and of the former glacial lake spillway. In southern Quebec, small ice-dammed lakes were numerous and important because they shaped the geomorphology of the region during the deglaciation. They are thus among the key components of a deglaciation model for this area.

Technical note Empirical algorithm using SeaWiFS hyperspectral bands: A simple test

The aim of this note is to test an empirical algorithm using spectral curvature theory at selected SeaWiFS hyerspectral bands, in order to estimate the chlorophyll pigment concentrations in the coastal waters of Baie des Chaleurs (Gulf of St. Lawrence). Simulated SeaWiFS algorithms require the measurement of reflectances with a high sensitive spectroradiometer as well as the responsitivity of SeaWiFS sensor at each band. Volume reflectances were taken using a hand held spectroradiometer simultaneously to measurements of in situ chlorophyll pigment concentrations. An empirical algorithm of the form: log (chlorophyll pigments) 0.92-0.46 Delta2 log R0sea(555) yields an estimate of chlorophyll pigment concentrations within a mean deltaC / C of 23%.

Technical Note Simulation of MEIS-II data on 5S code to quantify algal concentration in an intertidal area

Abstract An atmospheric correction algorithm due to Deschamps et al. (1981) has been applied to MEIS-II data. Some atmospheric conditions such as continental and maritime aerosol models have been used in this work. Simulation on 5S code was made with Thematic Mapper Band 4 and Spot band 3. All these pieces of the puzzle permitted the qualification of algal concentration in an intertidal area, which was the aim of this work. Continental or maritime aerosol models gave a similar result due probably to the specific area, located between land and nearshore. Apparent radiance is smaller than corrected radiance because absorption process takes place in this part of the spectrum (0.8 to 0.9μm). When apparent radiance is higher than 30 Wm−2 sr−1 μm−1 algal concentration is overestimated by up to 60 per cent.

Recreational uses of Québec coastlines

Estimated at the scale of 1:1 000 000, Quebec benefits from 9000 km of coastlines (Gaudreau et Gauthier, 1981). The coastlines of tourist region 18 (Figure 1), or the region that encompasses all of northern Quebec, is not equipped with any recreational installation whatsoever. Docks and small ports represent the only form of shelter available to hardy boaters. On the other hand, the 7000 km of coastlines of the St. Lawrence River system, corresponding to all southern Quebec, are relatively well equipped. By the St. Lawrence River system, we refer to the gulf (tourist region 01, 17 and five-sixth of region 02), the maritime and briny water estuaries affected by saltwater tides (tourist region 04, 07 and two-third of region 06), the limnetic estuary affected by fresh water (tourist regions 03, 05, 16, one-sixth of region 02 and one-third of region 06) and part of the river itself up to the province of Ontario border (tourist regions 09, 10, 11 and 12) (Figure 2). 5.