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Duanne A White - One of the best experts on this subject based on the ideXlab platform.
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late quaternary Glacial History constrains glacio isostatic rebound in enderby land east antarctica
Journal of Geophysical Research, 2014Co-Authors: Duanne A White, David FinkAbstract:Measurements of the loss or gain of ice mass from large ice sheets are presently achieved through satellite-based techniques such as GRACE (Gravity Recovery and Climate Experiment). The accuracy of these satellite-based measurements to changes in modern ice sheet mass depends on our knowledge of present-day glacio-isostatic crustal uplift rates caused by past ice sheet changes. To improve models of glacio-isostatic rebound in East Antarctica, we investigated ice histories along Rayner Glacier, Enderby Land, and a little explored sector of the ice sheet where GRACE data had suggested significant mass gain during the last decade. Observations from a recent Glacial geomorphic reconnaissance coupled with cosmogenic nuclide dating indicate that in the lower part of the Rayner Glacier, Enderby Land, ice heights lowered by at least 300 m and the calving margin retreated by at least 10 km in the early Holocene (~6 to 9 ka B.P.). The magnitude and timing of deglaciation are consistent with ice histories used to model the postGlacial rebound corrections for present-day GRACE mass trends. These observations strengthen the body of evidence that suggests ice mass gain in Enderby Land is presently partly offsetting mass loss in other parts of Antarctica.
Brenda L Hall - One of the best experts on this subject based on the ideXlab platform.
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holocene Glacial History of renland ice cap east greenland reconstructed from lake sediments
Quaternary Science Reviews, 2021Co-Authors: Aaron Medford, Brenda L Hall, Thomas V Lowell, Meredith A Kelly, Laura B Levy, Paul S Wilcox, Yarrow AxfordAbstract:Abstract Shrinking glaciers, melting permafrost, and reduced sea ice all indicate rapid contraction of the Arctic cryosphere in response to present-day climate warming, a trajectory that is expected to continue, if not accelerate. The reaction of the Arctic cryosphere to past periods of climate variation can afford insight into its present and future behavior. Here, we examine a ∼12,000 year record of glacier fluctuations and meltwater variation associated with the Renland Ice Cap, East Greenland, that extends from the early Holocene thermal optimum through the cooling of the Little Ice Age to present. Sediment records from Glacially fed lakes indicate rapid early Holocene deglaciation, with ice extent likely slightly smaller than at present by ∼9500 yr BP. Glacial activity resulted in occasional deposition of rock flour in the studied lakes in the early Holocene until at least ∼7500 yr BP. Rock flour is absent for much of the period ∼7000-4000 yr BP, suggesting ice extent generally was smaller than at present. However, thin layers of blue-gray clay throughout this period may indicate millennial-scale ice expansions, with Renland Ice Cap briefly reaching extents during cold phases that may have been similar to today. Glacial sediment deposition occurred again in the late Holocene at ∼3200–3400 yr BP and was followed by a brief Glacial episode at ∼1340 yr BP and then a major event beginning shortly after ∼1050 yr BP. We infer that rock flour deposition in the lakes in the last millennium corresponds with advance of Renland glaciers to their Little Ice Age positions, marked by a fresh, gray drift limit. Radiocarbon dates of in situ plant remains adjacent to the present ice cap indicate a short relatively warm period ∼500 yr ago, when ice was within its AD 2011 limit, followed by glacier readvance. The general pattern of ice fluctuations in Renland is similar to that at other ice caps in the region, but also has important differences, including the preservation of a possible mid-Holocene record at times when lower-elevation ice caps in the Scoresby Sund region may have been absent. This finding reinforces the concept that examination of multiple geographic and geomorphologic settings is necessary for a full understanding of ice variations in a region.
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holocene Glacial History of antarctica and the sub antarctic islands
Quaternary Science Reviews, 2009Co-Authors: Brenda L HallAbstract:Abstract A History of Holocene glaciation in the Antarctic and sub-Antarctic affords insight into questions concerning present and future ice-sheet and mountain-glacier behavior and global climate and sea-level change. Existing records permit broad correlation of Holocene ice fluctuations within the region. In several areas, ice extent was less than at present in mid-Holocene time. An important exception to this is the West Antarctic Ice Sheet, which has undergone continued recession throughout the Holocene, probably in response to internal dynamics. The first NeoGlacial ice advances occurred at ∼5.0 ka, although some sites (e.g., western Ross Sea) lack firm evidence for Glacial expansion at that time. Glaciers in all areas underwent renewed growth in the past millennium, and most have subsequently undergone recession in the past 50 years, ranging from near-catastrophic in parts of the Antarctic Peninsula to minor in the western Ross Sea region and sections of East Antarctica. This magnitude difference likely reflects the much greater warming that is taking place in the Antarctic Peninsula region today as compared to East Antarctica.
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lake ice conveyor deposits geomorphology sedimentology and importance in reconstructing the Glacial History of the dry valleys
Geomorphology, 2006Co-Authors: Brenda L Hall, Chris H Hendy, George H DentonAbstract:During the last Glacial maximum (LGM), lake-ice conveyors transported Glacial debris across the surface of large proGlacial lakes in the Dry Valleys region of Antarctica. The resulting sediments and landform assemblages are keys to interpreting the Glacial History of the Dry Valleys and, potentially, other areas of Antarctica. Paleoconveyor deposits occur in Taylor, Miers, Wright, and Victoria Valleys, as well as in many other parts of the region. Sediments typically consist of stratified to massive sand and/or silt grading upward into poorly sorted gravel, cobbles, and boulders. These sediments make up a variety of landforms, including mounds and moat line, cross-valley, and longitudinal ridges. The classic landform assemblage also displays an associated moraine bank, as well as deltas and shorelines.
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antarctic Glacial History since the last Glacial maximum an overview of the record on land
Antarctic Science, 1998Co-Authors: Ólafur Ingólfsson, Brenda L Hall, Christian Hjort, Paul Arthur Berkman, Svante Bjorck, Eric A Colhoun, I Goodwin, Kazuomi Hirakawa, Martin Melles, Per MollerAbstract:This overview examines available circum-Antarctic Glacial History archives on land, related to developments after the Last Glacial Maximum (LGM). It considers the Glacial-stratigraphic and morphologic records and also biostratigraphical information from moss banks, lake sediments and penguin rookeries, with some reference to relevant Glacial marine records. It is concluded that Holocene environmental development in Antarctica differed from that in the Northern Hemisphere. The initial deglaciation of the shelf areas surrounding Antarctica took place before 10 000 14C yrs before present(BP), and was controlled by rising global sea level. This was followed by the deglaciation of some presently ice-free inner shelf and land areas between 10 000 and 8000 yr BP. Continued deglaciation occurred gradually between 8000 yr BP and 5000 yr BP. Mid-Holocene Glacial readvances are recorded from various sites around Antarctica. There are strong indications of a circum-Antarctic climate warmer than today 4700–2000 yr BP. The best dated records from the Antarctic Peninsula and coastal Victoria Land suggest climatic optimums there from 4000–3000 yr BP and 3600–2600 yr BP, respectively. Thereafter NeoGlacial readvances are recorded. Relatively limited Glacial expansions in Antarctica during the past few hundred years correlate with the Little Ice Age in the Northern Hemisphere.
Nicolaj K Larsen - One of the best experts on this subject based on the ideXlab platform.
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Glacial History of inglefield land north greenland from combined in situ 10 be and 14 c exposure dating
Climate of The Past, 2020Co-Authors: Anne Sofie Sondergaard, Svend Funder, Nicolaj K Larsen, Jesper V Olsen, Olivia Steinemann, David L Egholm, Kurt H KjaerAbstract:Abstract. Determining the sensitivity of the Greenland Ice Sheet (GrIS) to Holocene climate changes is a key prerequisite for understanding the future response of the ice sheet to global warming. In this study, we present new information on the Holocene Glacial History of the GrIS in Inglefield Land, north Greenland. We use 10 Be and in situ 14 C exposure dating to constrain the timing of deglaciation in the area and radiocarbon dating of reworked molluscs and wood fragments to constrain when the ice sheet retreated behind its present-day extent. The 10 Be ages are scattered ranging from ca. 92.7 to 6.8 ka, whereas the in situ 14 C ages range from ca. 14.2 to 6.7 ka. Almost half of the apparent 10 Be ages predate the Last Glacial Maximum and up to 89 % are to some degree affected by nuclide inheritance. Based on the few reliable 10 Be ages, the in situ 14 C ages and existing radiocarbon ages from Inglefield Land, we find that the deglaciation along the coast commenced at ca. 8.6–8.3 ka cal BP in the western part and ca. 7.9 ka in the central part, following the opening of Nares Strait and arrival of warm waters. The ice margin reached its present-day position at ca. 8.2 ka at the Humboldt Glacier and ca. 6.7 ka in the central part of Inglefield Land. Radiocarbon ages of reworked molluscs and wood fragments show that the ice margin was behind its present-day extent from ca. 5.8 to 0.5 ka cal BP. After 0.5 ka cal BP, the ice advanced towards its Little Ice Age position. Our results emphasize that the slowly eroding and possibly cold-based ice in north Greenland makes it difficult to constrain the deglaciation History based on 10 Be ages alone unless they are paired with in situ 14 C ages. Further, combining our findings with those of recently published studies reveals distinct differences between deglaciation patterns of northwest and north Greenland. Deglaciation of the land areas in northwest Greenland occurred earlier than in north Greenland, and periods of restricted ice extent were longer, spanning the Middle and Late Holocene. Overall, this highlights past ice sheet sensitivity to Holocene climate changes in an area where little information was available just a few years ago.
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Glacial History of the greenland ice sheet and a local ice cap in qaanaaq northwest greenland
Journal of Quaternary Science, 2019Co-Authors: Anne Sofie Sondergaard, Nicolaj K Larsen, Jesper V Olsen, Astrid Strunk, Sarah A WoodroffeAbstract:In this study, we present new information on the Glacial History of the Greenland Ice Sheet (GrIS) and a local ice cap in Qaanaaq, northwest Greenland. We use geomorphological mapping, 10Be exposure dating of boulders, analysis of lake cores, and 14C dating of reworked marine molluscs and subfossil plants to constrain the Glacial History. Our 14C ages of reworked marine molluscs reveal that the ice extent in the area was at or behind its present‐day position from 42.2 ± 0.4 to 30.6 ± 0.3k cal a BP after which the GrIS expanded to its maximum position during the Last Glacial Maximum. We find evidence of early ice retreat in the deep fjord (Inglefield Bredning) at 11.9 ± 0.6 ka whereas the Taserssuit Valley was deglaciated ~4 ka later at 7.8 ± 0.1k cal a BP. A proGlacial lake record suggests that the local ice cap survived the Holocene Thermal Maximum but moss kill‐dates reveal that it was smaller than present for a period of time before 3.3 ± 0.1k until 0.9 ± 0.1k cal a BP, following which the ice in the area expanded towards its Little Ice Age extent.
Ólafur Ingólfsson - One of the best experts on this subject based on the ideXlab platform.
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cosmogenic 36cl exposure ages reveal a 9 3 ka bp glacier advance and the late weichselian early holocene Glacial History of the drangajokull region northwest iceland
Quaternary Science Reviews, 2015Co-Authors: Ólafur Ingólfsson, Skafti Brynjolfsson, Anders Schomacker, Jakob Klove KeidingAbstract:Abstract We present twenty-four new cosmogenic isotope ( 36 Cl) surface exposure ages from erratic boulders, moraine boulders and Glacially eroded bedrock that constrain the late Weichselian to Holocene Glacial History of the Drangajokull region, northwest Iceland. The results suggest a topographically controlled ice sheet over the Vestfirðir (Westfjords) peninsula during the last glaciation. Cold based non-erosive sectors of the ice sheet covered most of the mountains while fjords and valleys were occupied with erosive, warm-based ice. Old 36 Cl exposure ages from highlands and mountain plateaux (L8; 76.5 ka and H1; 41.6 ka) in combination with younger erratic boulders (L7; 26.2 and K1–K4; 15.0–13.8 ka) superimposed on such surfaces suggest the presence of non-erosive ice over uplands and plateaux in the Vestfirðir peninsula during the last glaciation. Glacially scoured terrain and erratic boulders yielding younger exposure ages (L1-L6; 11.3–9.1 ka and R1, R6-R7; 10.6–9.4 ka) in the lowland areas indicate that the valleys and fjords of the Vestfirðir peninsula were occupied by warm-based, dynamic ice during the last glaciation. The deglaciation of mountain Leirufjall by 26.2 ka BP suggests that ice thinning and deglaciation of some mountains and plateaux preceded any significant lateral retreat of the ice sheet. Subsequently this initial ice thinning was followed by break-up of the shelf based ice sheet off Vestfirðir about 15 ka BP. Hence, the new exposure ages suggest a stepwise asynchronous deglaciation on land, following the shelf break-up with some valleys and most of the highlands, ice free by 14–15 ka BP. The outermost moraine at the mouth of Leirufjorður is dated to 9.3 ka BP, and we suggest the moraine to be formed by a glacier re-advance in response to a cooler climate forced by the reduced Atlantic Meridional Overturning Circulation at around 9.3 ka BP. A system of moraines proximal to the 9.3 ka moraine in Leirufjorður as well as a 9.4 ka deglaciation age in the coastal area of Reykjarfjorður suggest that an extensive ice cap persisted over the eastern Vestfirðir peninsula at least until c. 9 ka BP.
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Arctic Ocean Glacial History
Quaternary Science Reviews, 2014Co-Authors: Martin Jakobsson, Dayton Dove, Karin Andreassen, Lilja Rún Bjarnadóttir, Julian A. Dowdeswell, John England, Svend Funder, K. Hogan, Ólafur Ingólfsson, Anne E. JenningsAbstract:While there are numerous hypotheses concerning Glacial interGlacial environmental and climatic regime shifts in the Arctic Ocean, a holistic view on the Northern Hemisphere's late Quaternary ice-sh ...
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4 deglaciation and holocene Glacial History of iceland
Developments in Quaternary Science, 2010Co-Authors: Ólafur Ingólfsson, Hreggviður Norðdahl, Anders SchomackerAbstract:Abstract Iceland was heavily glaciated at the Last Glacial Maximum – glaciers extended towards the shelf break. Ice thickness reached 1,500±500 m. The rapid deglaciation, starting 17.5–15.4 cal. kyr BP, was controlled by rising global sea level. The marine part of the ice sheet collapsed 15.4–14.6 cal. kyr BP and glaciers retreated inside the present coastline. In Younger Dryas, 12.6–12.0 cal. kyr BP, the ice sheet readvanced and terminated near the present coastline. After 11.2 cal. kyr BP the ice sheet retreated rapidly and relative sea level fell towards and eventually below present sea level at 10.7 cal. kyr BP. At 8.7 cal. kyr BP glaciers terminated proximal to their present margins. During the mid-Holocene climate optimum some of the present-day ice caps were probably absent. Ice caps expanded after 6.0–5.0 cal. kyr BP, and most glaciers reached their Holocene maxima during the Little Ice Age (AD 1300–1900).
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antarctic Glacial History since the last Glacial maximum an overview of the record on land
Antarctic Science, 1998Co-Authors: Ólafur Ingólfsson, Brenda L Hall, Christian Hjort, Paul Arthur Berkman, Svante Bjorck, Eric A Colhoun, I Goodwin, Kazuomi Hirakawa, Martin Melles, Per MollerAbstract:This overview examines available circum-Antarctic Glacial History archives on land, related to developments after the Last Glacial Maximum (LGM). It considers the Glacial-stratigraphic and morphologic records and also biostratigraphical information from moss banks, lake sediments and penguin rookeries, with some reference to relevant Glacial marine records. It is concluded that Holocene environmental development in Antarctica differed from that in the Northern Hemisphere. The initial deglaciation of the shelf areas surrounding Antarctica took place before 10 000 14C yrs before present(BP), and was controlled by rising global sea level. This was followed by the deglaciation of some presently ice-free inner shelf and land areas between 10 000 and 8000 yr BP. Continued deglaciation occurred gradually between 8000 yr BP and 5000 yr BP. Mid-Holocene Glacial readvances are recorded from various sites around Antarctica. There are strong indications of a circum-Antarctic climate warmer than today 4700–2000 yr BP. The best dated records from the Antarctic Peninsula and coastal Victoria Land suggest climatic optimums there from 4000–3000 yr BP and 3600–2600 yr BP, respectively. Thereafter NeoGlacial readvances are recorded. Relatively limited Glacial expansions in Antarctica during the past few hundred years correlate with the Little Ice Age in the Northern Hemisphere.
David Fink - One of the best experts on this subject based on the ideXlab platform.
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late quaternary Glacial History constrains glacio isostatic rebound in enderby land east antarctica
Journal of Geophysical Research, 2014Co-Authors: Duanne A White, David FinkAbstract:Measurements of the loss or gain of ice mass from large ice sheets are presently achieved through satellite-based techniques such as GRACE (Gravity Recovery and Climate Experiment). The accuracy of these satellite-based measurements to changes in modern ice sheet mass depends on our knowledge of present-day glacio-isostatic crustal uplift rates caused by past ice sheet changes. To improve models of glacio-isostatic rebound in East Antarctica, we investigated ice histories along Rayner Glacier, Enderby Land, and a little explored sector of the ice sheet where GRACE data had suggested significant mass gain during the last decade. Observations from a recent Glacial geomorphic reconnaissance coupled with cosmogenic nuclide dating indicate that in the lower part of the Rayner Glacier, Enderby Land, ice heights lowered by at least 300 m and the calving margin retreated by at least 10 km in the early Holocene (~6 to 9 ka B.P.). The magnitude and timing of deglaciation are consistent with ice histories used to model the postGlacial rebound corrections for present-day GRACE mass trends. These observations strengthen the body of evidence that suggests ice mass gain in Enderby Land is presently partly offsetting mass loss in other parts of Antarctica.
