@article {2529, title = {Holocene climate and environmental history of East Greenland inferred from lake sediments}, journal = {Journal of Paleolimnology}, volume = {57}, year = {2017}, month = {Jan-04-2017}, pages = {321 - 341}, abstract = {Prediction of future Arctic climate and environmental changes, as well as associated ice-sheet behavior, requires placing present-day warming and reduced ice extent into a long-term context. Here we present a record of Holocene climate and glacier fluctuations inferred from the paleolimnology of small lakes near Istorvet ice cap in East Greenland. Calibrated radiocarbon dates of organic remains indicate deglaciation of the region before ~10,500 years BP, after which time the ice cap receded rapidly to a position similar to or less extensive than present, and lake sediments shifted from glacio-lacustrine clay to relatively organic-rich gyttja. The lack of glacio-lacustrine sediments throughout most of the record suggests that the ice cap was similar to or smaller than present throughout most of the Holocene. This restricted ice extent suggests that climate was similar to or warmer than present, in keeping with other records from Greenland that indicate a warm early and middle Holocene. Middle Holocene magnetic susceptibility oscillations, with a ~200-year frequency in one of the lakes, may relate to solar influence on local catchment processes. Following thousands of years of restricted extent, Istorvet ice cap advanced to within 365 m of its late Holocene limit at ~AD 1150. Variability in the timing of glacial and climate fluctuations, as well as of sediment organic content changes among East Greenland lacustrine records, may be a consequence of local factors, such as elevation, continentality, water depth, turbidity, and seabirds, and highlights the need for a detailed spatial array of datasets to address questions about Holocene climate change.}, keywords = {De Vries cycle, Glacially fed lakes, Greenland, Holocene, Paleoclimate}, issn = {0921-2728}, doi = {10.1007/s10933-017-9951-5}, url = {http://link.springer.com/10.1007/s10933-017-9951-5}, author = {Lusas, Amanda R. and Hall, Brenda L. and Lowell, Thomas V. and Kelly, Meredith A. and Bennike, Ole and Levy, Laura B. and Honsaker, William} } @article {54, title = {Holocene fluctuations of Bregne ice cap, Scoresby Sund, east Greenland: a proxy for climate along the Greenland Ice Sheet margin}, journal = {APEX II: Arctic Palaeoclimate and its Extremes}, volume = {92}, year = {2014}, pages = {357-368}, abstract = {The Greenland Ice Sheet is a major component of the Arctic cryosphere and the magnitude of its response to future climate changes remains uncertain. Longer-term records of climate near the ice sheet margin provide information about natural climate variability and can be used to understand the causes of past changes in the Greenland Ice Sheet. As a proxy for Holocene climate near the ice sheet margin, we reconstruct the fluctuations of Bregne ice cap in the Scoresby Sund region of central east Greenland. Bregne is a small ice cap (2.5 km2 in area) and responds sensitively to summer temperatures. We employ a multi-proxy approach to reconstruct the ice cap fluctuations using geomorphic mapping, 10Be ages of boulders and bedrock and lake sediment records. Past extents of Bregne ice cap are marked by moraines and registered by sediments in downvalley lakes. 10Be ages of bedrock and boulders outboard of the moraines indicate that Bregne ice cap was within \~{}250 m of its present-day limit by at least 10.7 ka. Multi-proxy data from sediments in Two Move lake, located downvalley from Bregne ice cap, indicate that the ice cap likely completely disappeared during early and middle Holocene time. Increasing magnetic susceptibility and percent clastic material from \~{}6.5 to \~{}1.9 cal ka BP in Two Move lake sediments suggest progressively colder conditions and increased snow accumulation on the highlands west of the lake. Laminated silt deposited at \~{}2.6 cal ka BP and \~{}1.9 cal ka BP to present registers the onset and persistence of Bregne ice cap during the late Holocene. 10Be ages of boulders on an unweathered, unvegetated moraine in the Bregne ice cap forefield range from 0.74 to 9.60 ka. The youngest 10Be age (0.74 ka) likely represents the age of the moraine whereas older ages may be due to 10Be inherited from prior periods of exposure. This late Holocene moraine marks the second largest advance of the ice cap since deglaciation of the region at the end of the last ice age. The oldest moraine in the forefield dates to <=2.6 cal ka BP. The fluctuations of Bregne ice cap were likely influenced by Northern Hemisphere summer insolation throughout the Holocene and abrupt late Holocene cold events.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2013.06.024}, url = {http://www.sciencedirect.com/science/article/pii/S0277379113002448}, author = {Levy, Laura B. and Kelly, Meredith A. and Lowell, Thomas V. and Hall, Brenda L. and Hempel, Laura A. and Honsaker, William M. and Lusas, Amanda R. and Howley, Jennifer A. and Axford, Yarrow L.} } @article {92, title = {Late Holocene expansion of Istorvet ice cap, Liverpool Land, east Greenland}, journal = {Quaternary Science Reviews}, volume = {63}, year = {2013}, note = {id: 2290}, pages = {128-140}, abstract = {The Greenland Ice Sheet is undergoing dynamic changes that will have global implications if they continue into the future. In this regard, an understanding of how the ice sheet responded to past climate changes affords a baseline for anticipating future behavior. Small, independent ice caps adjacent to the Greenland Ice Sheet (hereinafter called {\textquotedblleft}local ice caps{\textquotedblright}) are sensitive indicators of the response of Greenland ice-marginal zones to climate change. Therefore, we reconstructed late Holocene ice-marginal fluctuations of the local Istorvet ice cap in east Greenland, using radiocarbon dates of subfossil plants, 10Be dates of surface boulders, and analyses of sediment cores from both threshold and control lakes. During the last termination, the Istorvet ice cap had retreated close to its maximum Holocene position by \~{}11,730 cal yr BP. Radiocarbon dates of subfossil plants exposed by recent recession of the ice margin indicate that the Istorvet cap was smaller than at present from AD 200 to AD 1025. Sediments from a threshold lake show no glacial input until the ice cap advanced to within 365 m of its Holocene maximum position by \~{}AD 1150. Thereafter the ice cap remained at or close to this position until at least AD 1660. The timing of this, the most extensive of the Holocene, expansion is similar to that recorded at some glaciers in the Alps and in southern Alaska. However, in contrast to these other regions, the expansion in east Greenland at AD 1150 appears to have been very close to, if not at, a maximum Holocene value. Comparison of the Istorvet ice-cap fluctuations with Holocene glacier extents in Southern Hemisphere middle-to-high latitude locations on the Antarctic Peninsula and in the Andes and the Southern Alps suggests an out-of-phase relationship. If correct, this pattern supports the hypothesis that a bipolar see-saw of oceanic and/or atmospheric circulation during the Holocene produced asynchronous glacier response at some localities in the two polar hemispheres.}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2012.11.012}, url = {http://www.sciencedirect.com/science/article/pii/S0277379112004830}, author = {Lowell, Thomas V. and Hall, Brenda L. and Kelly, Meredith A. and Bennike, Ole and Lusas, Amanda R. and Honsaker, William and Smith, Colby A. and Levy, Laura B. and Travis, Scott and Denton, George H.} }