The status of Icelandic ice caps during the early Holocene provides important constraints on North Atlantic climate and the mechanisms behind natural climate variability. A recent study postulates that Drangajökull on Vestfirðir, Iceland, persisted through the Holocene Thermal Maximum (HTM, 7.9–5.5 ka) and may be a relic from the last glacial period. We test this hypothesis with a suite of sediment cores from threshold lakes both proximal and distal to the ice cap's modern margin. Distal lakes document rapid early Holocene deglaciation from the coast and across the highlands south of the glacier. Sediment from Skorarvatn, a lake to the north of Drangajökull, shows that the northern margin of the ice cap reached a size comparable to its contemporary limit by ∼10.3 ka. Two southeastern lakes with catchments extending well beneath modern Drangajökull confirm that by ∼9.2 ka, the ice cap was reduced to ∼20% of its current area. A continuous 10.3ka record of biological productivity from Skorarvatn's sediment indicates local peak warmth occurred between 9 and 6.9 ka. The combination of warm and dry summers on Vestfirðir suggests that Drangajökull very likely melted completely shortly after 9.2 ka, similar to most other Icelandic ice caps.
Bibliographical noteFunding Information:
This project was supported by RANNIS (grant # 130775051 ) and the RANNIS Grant-of-Excellence (grant # 141573-052 ) awarded by the Icelandic Center for Research to Á. Geirsdóttir and G.H. Miller and a University of Iceland PhD grant awarded to K. Zalzal from 2010 to 2012. We thank þorsteinn Jónsson, Sveinbjörn Steinþórsson, Chris Florian and Celene Blair for lake coring assistance. Sydney Gunnarson and Brynja Berndsen (UoI) helped analyze Gjögurvatn′s sediment and tephra record and Eric Gunderson (UCB) assisted in developing the BSi record, for which all of their help is greatly appreciated. Finally, we thank the editor and one anonymous reviewer for constructive reviews which helped strengthen the manuscript.
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- Threshold lakes
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