Fluctuations des fronts glaciaires dans le sud de la Passe d'Akshayuk, parc National d'Auyuittuq, Nunavut (French text).

摘要

This thesis discusses the actual and modern ice margin fluctuations of valley and cirque glaciers in South Akshayuk Pass, Auyuittuq National Park (Baffin Island, NU). The fluctuation of the ice margins of the Tete de Cirque, Glacier 12, Windy Lake, Niflheim and Glacier 20A glaciers were analysed using geometrically rectified aerial photographs taken between 1948 and 1977. IKONOS and LANDSAT 7 ETM+ satellite imagery covering the 1977 to 2003 period were also used. The results indicate a mean annual ice margin retreat of 8.9 m per year during the 1948 to 2003 period. Compared to south and west-facing glaciers, the ones facing north are characterize by a smaller annual retreat rate. Ice margin fluctuations since the Little Ice Age were evaluated using lichenometric measurements of Rhizocarpon geographicum found on the moraines of the Turnweather, Tete de Cirques, Glacier 12, Windy Lake, Niflheim, Glacier 20A and Sivingavuk glaciers. Moraine ages were determined by measuring the 10 largest-diameter R. geographicum thalli in the sampling area (100 m2) and converting these measurements to ages using the regional growth curve of R. geographicum . The maximum extent of the ice margins of the valley and cirques glaciers was reached between AD 800 to 1860, mainly between 1840 and 1860 at the end of the Little Ice Age period. Size-frequency distribution, an analysis of variance, and multiple comparisons showed that some moraines were subjected to local environmental variations, which affected the growth of R. geographicum, with subsequent implications in the interpretation of the lichenometric ages of the moraines and the ice margin fluctuations.