| Summary: | Earth`s polar regions are undergoing dramatic changes due to ongoing climate change as demonstrated by increasing temperatures, collapsing ice shelves, Arctic sea ice loss and rapid glacier retreat. Driving an accelerating rise in global sea level, this amplified regional response may have devastating global socio-economic consequences in the foreseeable future. Yet the causes and range of polar climate variability remain poorly understood as observational records are short and fragmentary, while climate proxy timeseries remain scarce and often lack resolution. More detailed and longer paleoclimate archives are urgently needed to allow assessment of the full envelope of natural polar climate variability. This would allow us to contextualise ongoing warming and help improve policy scenarios, in effect using the past as the key to both present and future. Glaciers are sensitive recorders of climate variability as demonstrated by their response to ongoing global change. In addition to changes in size, this response is also captured by variations in glacial erosion in alpine glacier systems. The finest constituent of this process, known as glacial flour, is suspended in meltwater streams and may be deposited in downstream lakes. Hence, the bottom sediments of such glacier-fed lakes are continuous archives of past glacier activity and thus represent prime targets for paleoclimate studies. In this thesis, the paleoclimatic potential of glacier-fed lake sediments is harnessed to improve our understanding of past polar climate change. To this end, sensitive sites on Arctic Svalbard and Antarctic South Georgia, in the pathways of major regional circulation patterns, were targeted. Emphasis is placed on the present Holocene interglacial as it is characterised by climatic boundary conditions that are similar to the present. A targeted multi-proxy approach, concentrating on geomorphological mapping, sediment fingerprinting, paleothermometry and advanced numerical techniques, was employed to enhance the potential of ...
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