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Larsen, Darren ¹ ; Miller, Gifford ² ; Geirsdottir, Aslaug ³

¹ Dept. of Geological Sciences/INSTAAR
² Dept. of Geological Sciences/INSTAAR
³ Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland

Records of past glacier fluctuations are an important source of paleoclimate data and provide context for future changes in global ice volume. In the North Atlantic region, glacier chronologies can be used to track the response of terrestrial environments to variations in marine conditions including circulation patterns and sea ice cover. However, the majority of glacier records are discontinuous and temporally restricted, owing in part to the extensive advance of Northern Hemisphere glaciers during the Little Ice Age, the most recent and severe climate anomaly of the Neoglacial period. We present an absolutely dated and continuous record of Icelandic ice cap and outlet glacier fluctuations through the past 1.2 ka using varved sediments from Hvítárvatn, a proglacial lake adjacent to Langjökull ice cap (~925 km2). Large spatial and temporal variations in sediment flux are related to changing ice cap dimensions and are reconstructed from six sediment cores and seismic reflection profiles. Sediment data reveal two discrete phases of ice expansion occurring ca. 1400 to 1550 AD and ca. 1680 to 1890 AD. These advances are separated by a persistent interval of retreat or glacier stillstand, suggesting that a substantial period of warming interrupted LIA cooling. The pattern of Icelandic glacier activity contrasts with that of European glaciers but shows strong similarities to reconstructed changes in North Atlantic oceanographic conditions, indicating differing regional responses to coupled ocean-atmosphere-sea ice variations.