| Summary: | This thesis examines the spatial and temporal expression of Holocene glacier fluctuations in southeast Iceland. The study uses geomorphological evidence to reconstruct the former extent of Lambatungnajökull -a non-surging, valley glacier flowing from the eastern flank of the Vatnajökull ice-cap. Lichenometry is used to date recent glacial landforms and decode the pattern of glacier fluctuations over the last 300 years. Tephrochronology is used to date older features (<10,000 yr). The results show a pattern of fluctuations driven by climatic change. During the Lateglacial-Early Holocene Period the glacier terminus was situated at the present-day coastline. The ice-margin has retreated c. 20 km during the last 10,000 years. At least four periods of glacier re-advance have been identified, at c. 5000,3000,1600 and 170 years BP. Overall, the cumulative ice recession since c. 10 ka BP represents an ELA rise of c. 400 m which equates to an increase in mean air temperature of at least 2°C, assuming constant precipitation levels. Since the late 181" century, Lambatungnajökull has been in overall retreat. Moraines dated using two different lichenometric techniques indicate that the most extensive period of glacier expansion during historical time culminated shortly before c. AD 1795, probably in the 1780s. Recession over the last 200 years has been interrupted by re-advances in the 1850s, 1870s, and c. AD 1890. In the 20`h century, most notably in the 1930s and 1940s, Lambatungnajökull receded more rapidly than at any time during the previous 150 years. However, brief cold spells (-5 yrs), centred around the years AD 1918 and AD 1964, temporarily halted glacier recession. Lambatungnajökull has only retreated slightly over the last 20 years. The degree and nature of glacier retreat since 1930 compares well with similar-sized glaciers in southern Iceland. Furthermore, the pattern of glacier fluctuations over the last 150 years reflects the temperature oscillations recorded at nearby meteorological stations. Much of ...
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