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  • 1
    Keywords: Kongreßschrift
    Type of Medium: Book
    Pages: 88 S , Graph. Darst , 1 Beil. : 9 Bl.
    Language: Undetermined
    Note: Beil. u.d.T.: Sea ice in the climate system: lessons from the North Atlantic Arctic / Miller, Geirsdottir and Koerner , Enth. 40 Beitr.
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  • 2
    ISSN: 1751-8369
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography , Geosciences
    Notes: Evidence from north-west Iceland's shelf and fjords is used to develop a scenario for environmental change during the last 36 cal Ky. The retreat history of the Iceland Ice Cap during the last deglaciation is delineated through lithofacies studies, carbon analyses and magnetic susceptibility, and studies of ice-rafted debris (IRD) in sediment cores. Sedimentological data from lake Efstadalsvatn, Vestfirdir peninsula, trace the glacier retreat on land. In two of the high resolution shelf cores we detect near continuous IRD accumulation from 36 to 11 cal Kya. However, IRD is absent in the cores from ca. 22 to 19 cal Kya, possibly indicating more extensive landfast sea ice conditions. All cores show intensified IRD during the Younger Dryas chronozone; the fjord cores show a continuous IRD record until 10 cal Kya. Magnetic susceptibility and carbon analyses from Efstadalsvatn reveal the disappearance of local ice in the basin just before 10.5 cal Kya. No IRD was detected in the sediment cores during 10 to Ø4 cal Kya. Some indication of cooling occurs between 4 and 3 cal Kya, with a fresh input of IRD in fjord cores after 1 cal Kya.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1751-8369
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography , Geosciences
    Notes: Djúpáll is a Ø90 km long by 15 km wide trough which extends from Ísafjardardjúp to the shelf break above Blosseville Basin, north of the Denmark Strait. We present 3.5 kHz seismic profiles from this trough and data from cores collected in 1996 (JM96-1232 and −1234) and five cores collected on cruise B997. We pay particular attention to B997-338 as this core recovered sediments ranging in age between 12 and 36 cal. Ky BP. This is the first such record from the Iceland continental shelf. Dating control is provided by AMS 14C dates and the occurrence of the Saksunarvatn tephra. X-radiographs of the cores enable us to quantify the input of iceberg-rafted detritus (IRD) and to describe the lithofacies. The sediment matrix is fine-grained and might represent either rain-out of suspended sediment plumes or distal turbidites. IRD is present from ca. 12 cal. Ky BP throughout the next 24 cal. Ky with some IRD-free intervals. Using sediment magnetic properties, sampled at 1 cm (ø100 yrs/sample) resolution, we provide a stacked environmental record which includes marine isotope stages 1, 2 and part of 3. The sediment magnetic properties kARM and IRM(60), and carbonate and TOC, show multi-millennia quasi-periodic cycles, but there are no obvious events coeval with the North Atlantic Heinrich events. Our data indicate that at the Last Glacial Maximum on the Vestfirdir peninsula (VP), north-west Iceland, ice did not reach the shelf break, but was probably grounded near the mouth of Ísafjardardjúp. A rapid increase in the rate of sediment accumulation suggests that deglaciation of the VP occurred mainly between 11 and 15 cal. Ky BP.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The oceanographic Polar Front separates the East Greenland and Iceland margins. Surface water temperatures across Denmark Strait vary by 8–12 °C and represent one of the steepest oceanographic gradients on earth. The East Greenland margin is a polar environment, with extensive sea-ice cover and calving glacier margins; in contrast, the Iceland shelf is much more temperate, and freshwater run-off is a key component in land–ocean sediment transfers. Average sediment properties from these two contrasting climate and oceanographic continental shelf environments are compared in the spatial domain at 13 sites; the data represent the last 10 000 radiocarbon years of `normal' marine sedimentation for the two regions. The two regions have similar average rates of sediment accumulation (around 43·5 cm kyr−1), so that this key variable is factored out in explaining any differences in sediment properties. Dry sediment density, moisture content, hygroscopic moisture, total organic carbon and carbonate contents, mass magnetic susceptibility and the percentages of sand and silt are compared focusing on: (1) median values for sediment properties; and (2) downcore variability, measured by the coefficient of variation (CV). There are significant differences in all but one (hygroscopic moisture) of the sediment properties between Iceland and East Greenland; in four cases, the sense of the differences was not as predicted. In terms of downcore variation (CV), no difference was found between the two regions, nor between the 13 sites, whereas there are some significant differences between the variables. Carbonate and mass magnetic susceptibility have the largest spreads, and moisture content and dry sediment density are the least variable. Protocols are developed to identify the `type core' in a regional series of sites. The results indicate a need to develop a regional perspective on sediment properties, both as inputs to models of sedimentary processes in different polar/arctic environments, and as an indication of which sediment properties might be best suited for palaeoenvironmental downcore time series.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Terra nova 8 (1996), S. 0 
    ISSN: 1365-3121
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Glaciers and volcanoes have been the trademark of Iceland for centuries. The glaciers now cover ≅10% of the country and the volcanic regions are covered by lava flows every 5–10 kyr on average. Naturalists have concentrated on these two aspects, making notes on volcanic eruptions and traveling along the glacier margins ever since the first settlement of Iceland in the ninth century in some of the earliest episodes of geological research. Systematic studies of the glaciers began in the latter half of the 18th century. Even earlier, features such as striations and moraines were discovered and described in locations remote from the contemporary glacier margins. These features were interpreted as the effect of a much more extensive ice sheet on the island. At the beginning of the 20th century the discussion of the origin of sediments was unseparable from the age problem. From 1910 to 1950 very few new data were presented on the glaciation history of Iceland. A few sporadic publications either accepted or rejected previous conclusions. Systematic geological mapping of the country started in the wake of World War II encouraged by the acceptance of the plate tectonic theory in the late sixties. One of the most important results of this revived mapping effort was the identification of interbedded sediments interpreted as glacial deposits. Around 1975 Iceland was known in the geological literature for preserving more numerous glacial deposits than found elsewhere on land in the northern hemisphere. Over the last few years, systematic lithofacies analysis of sediments interbedded within lava flows has been conducted with the aim of delineating the earliest glaciation of Iceland and the periodicity of glaciation through the Tertiary and Quaternary. The results show a gradual growth of ice from south-east towards the north and west during the Pliocene-Pleistocene transition interrupted by periods of recessions and intermittent ice-free conditions.
    Type of Medium: Electronic Resource
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  • 6
    Publication Date: 2016-04-08
    Description: Clay- and silt-size mineral assemblages are described from eight piston cores from the fiords and shelf on the western margin of Baffin Bay, Arctic Canada. Radiocarbon dates indicate that all the cores extend back in time to the last local glacial/interglacial transition (i.e. 8–10 ka); four extend back to between 10 and 12 ka, and HU77-021-156, located on the Southeast Baffin Island shelf, includes the entire late Foxe glacial stage. Silt- and clay-size particles constitute ca 40 and 55%, respectively, by weight of the bulk sediment. The clay-size fraction is dominated by mica; feldspars and quartz are the main constituents of the silt fraction. The fiord sediments are mainly composed of local mineralogies, but on the shelf, and at times in the fiords, exotic mineral species occur. The most important of these are detrital carbonates, derived from erosion of the Paleozoic basins in Arctic Canada and/or northwest Greenland. Both calcite and dolomite occur; calcite is the major carbonate mineral in the “southern” cores, whereas dolomite is the most abundant in cores north of 66°N. Higher inputs of carbonate species occur during regional deglaciation, 7–10 ka, and during the last 5 ka (probably reflecting increased iceberg production from northwest Greenland). Thus variations in the precentages of the carbonate minerals indicate significant shifts in Late Quaternary glacial-sediment source areas and oceanographic regimes.
    Type: Article , PeerReviewed
    Format: text
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  • 7
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    PANGAEA
    In:  Supplement to: Andrews, John T; Cabedo-Sanz, Patricia; Jennings, Anne E; Olafasdottir, Saedis; Belt, Simon T; Geirsdóttir, Áslaug (2017): Sea ice, ice-rafting, and ocean climate across Denmark Strait during rapid deglaciation (~16 to 12 cal ka BP) of the Iceland and East Greenland shelves. Journal of Quaternary Science, https://doi.org/10.1002/jqs.3007
    Publication Date: 2023-01-13
    Description: Geophysical data from the Kangerlussuaq Trough, E Greenland (Dowdeswell et al., 2010; Stein, 1996), and from the West Iceland shelf (Syvitski et al., 1999) indicate that there are sites where pre Last Glacial Maximum (LGM) sediments exist, but no such sites have been successfully cored. However, a significant number of cores have been recovered that penetrate a basal diamicton, sometimes containing shells and foraminifera, and which are overlain by glacial marine sediments rich in ice rafted debris (IRD) (Jennings et al., 2000; Olafsdottir, 2004). At the LGM, reconstructions and marine field data (Andrews, 2008; Andrews et al., 1998, 2000; Dunhill, 2005; Funder et al., 2004; Hubbard et al., 2006; Vasskog et al., 2015) indicate that the Iceland and Greenland ice sheets were terminating at their shelf breaks with deposition on the slopes above the Denmark Strait. Active sediment deposition ceased on the Kangerlussuaq Trough Mouth Fan (KTMF) ca. 15.3 ka 14C BP (Andrews et al., 1998; Dunhill, 2005) and retreat to the present coastline occurred prior to deposition of the Vedde tephra (Jennings et al., 2006). There is strong evidence that a major change in deep-water circulation at ~15 cal ka BP resulted in abrupt warming at the onset of the Bølling/Allerød (B/A) interstadial (Thiagarajan et al., 2014; Thornalley et al., 2011). Syvitski et al (1999) and Norddahl and Ingolfsson (2015) argued that the Iceland Ice Sheet retreated rapidly during this time, driven by a rapid rise in relative sea level. Jennings et al. (2006) also presented radiocarbon evidence from marine cores for a rapid retreat of the Greenland Ice Sheet along Kangerlussuaq Trough (KT, Fig. 1).
    Type: Dataset
    Format: application/zip, 9 datasets
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  • 8
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    PANGAEA
    In:  Supplement to: Pendleton, Simon; Miller, Gifford H; Anderson, Robert A; Crump, Sarah E; Zhong, Yafang; Jahn, Alexandra; Geirsdóttir, Áslaug (2017): Episodic Neoglacial expansion and rapid 20th Century retreat of a small ice cap on Baffin Island, Arctic Canada and modeled temperature change. Climate of the Past Discussions, 1-15, https://doi.org/10.5194/cp-2017-27
    Publication Date: 2023-01-13
    Description: Records of Neoglacial glacier activity in the Arctic constructed from moraines are often incomplete due to a preservation bias toward the most extensive advance, usually the Little Ice Age. Recent warming in the Arctic has caused extensive retreat of glaciers over the past several decades, exposing preserved landscapes complete with in situ tundra plants previously entombed by ice. The radiocarbon ages of these plants define the timing of snowline depression and glacier advance across the site, in response to local summer cooling. Although most dead plants recently exposed by ice retreat are rapidly removed from the landscape by erosion, where erosive processes are unusually weak, dead plants may remain preserved on the landscape for decades. In such settings, a transect of plant radiocarbon ages can be used to construct a near-continuous chronology of past ice margin advance. Here we present radiocarbon dates from the first such transect on Baffin Island, which directly dates the advance of a small ice cap over the past two millennia. The nature of ice expansion between 20 BCE and ~1000 CE is still uncertain, but episodic advances at ~1000, ~1200, and ~1500 CE led to the maximum Neoglacial dimensions ~1900 CE. We employ a two-dimensional numerical glacier model to reconstruct the pattern of ice expansion inferred from the radiocarbon ages and to explore the sensitivity of the ice cap to temperature change. Model experiments show that at least ~0.44 °C of cooling over the past 2 ka is required for the ice cap to reach its 1900 margin, and that the period from ~1000 to 1900 CE must have been at least 0.25 °C cooler than the previous millennium; results that agree with regional climate model simulations. However, ~3 °C of warming since 1900 CE is required to explain retreat to its present position, and, at the same rate of warming, the ice cap will disappear before 2100 CE.
    Keywords: Baffin Island; Divide_Ice_Cap; ICEM; Ice measurement
    Type: Dataset
    Format: application/zip, 754.2 kBytes
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  • 9
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    PANGAEA
    In:  Supplement to: Harning, David J; Andrews, John T; Belt, Simon T; Cabedo-Sanz, Patricia; Geirsdóttir, Áslaug; Dildar, Nadia; Miller, Gifford H; Sepúlveda, Julio (2019): Sea Ice Control on Winter Subsurface Temperatures of the North Iceland Shelf During the Little Ice Age: A TEX86 Calibration Case Study. Paleoceanography and Paleoclimatology, 34(6), 1006-1021, https://doi.org/10.1029/2018PA003523
    Publication Date: 2023-02-12
    Description: Holocene paleoceanographic reconstructions along the North Iceland Shelf have employed a variety of sea surface temperature and sea ice proxies. However, these surface proxies tend to have a seasonal bias toward spring/summer and thus only provide a discrete snapshot of surface conditions during one season. Furthermore, sea surface temperature proxies can be influenced by additional confounding variables resulting in markedly different Holocene temperature reconstructions. Here, we expand Iceland's marine paleoclimate toolkit with TEX86 L: a temperature proxy based on the distribution of archaeal glycerol dibiphytanyl glycerol tetraether (GDGT) lipids. We develop a local Icelandic calibration from 21 surface sediment samples covering a wide environmental gradient across Iceland's insular shelves. Locally calibrated GDGT results demonstrate that (1) TEX86 L reflects winter subsurface (0-200 m) temperatures on the North Iceland Shelf and (2) our calibration produces more realistic temperature estimates with substantially lower uncertainty (S.E. ±4 °C) over global calibrations. We then apply this new calibration to a high‐resolution marine sediment core (last millennium) collected from the central NIS with age control constrained by 14C‐dated mollusks. To test the veracity of the GDGT subsurface temperatures, we analyze quartz and calcite wt% and a series of highly branched isoprenoid alkenes, including the sea ice biomarker IP25, from the same core. The sediment records demonstrate that the development of thick sea ice during the Little Ice Age warmed the subsurface due to winter insulation. Importantly, this observation reflects a seasonal component of the sea ice/ocean feedback to be considered for the nonlinear cooling of the Little Ice Age in and around Iceland.
    Keywords: (9Z)-2,6,10,14-Tetramethyl-7-(3-methylpent-4-enyliden)pentadeca-9-ene per unit sediment mass; 2,6,10,14-Tetramethyl-7-(3-methylpent-4-enyl)pentadecane per unit sediment mass; Acyclic glycerol dialkyl glycerol tetraether; Age; AGE; B997-316; Crenarchaeol; Crenarchaeol regio-isomer; DEPTH, sediment/rock; Dicyclic glycerol dialkyl glycerol tetraether; Diene II per unit sediment mass; GGC; Giant gravity corer; Glycerol dialkyl glycerol tetraethers; Monocyclic glycerol dialkyl glycerol tetraether; North Icelandic Shelf; Sample ID; Temperature, water, winter; Tetraether index of 86 carbon atoms, low-temperature region; Tricyclic glycerol dialkyl glycerol tetraether
    Type: Dataset
    Format: text/tab-separated-values, 490 data points
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  • 10
    Publication Date: 2023-06-09
    Keywords: Astrononion gallowayi; B997-338; Buccella frigida; Buccella frigida var. calida; Calcite; Calendar age; Carbon, organic, total; Carbonates; Cassidulina neoteretis; Cassidulina obtusa; Cassidulina reniforme; Cibicides lobatulus; Cibicides lobatulus, δ13C; Cibicides lobatulus, δ13C standard deviation; Cibicides lobatulus, δ18O; Cibicides lobatulus, δ18O standard deviation; Confusion Index; DEPTH, sediment/rock; Diene II per unit sediment mass; Dry unit; Elphidium excavatum; Ice rafted debris; Islandiella norcrossi; Kalifeldspar; Magnetic susceptibility, mass; Median, grain size; Mode, grain size, description; Neogloboquadrina pachyderma sinistral; Nonion labradoricum; PC; Piston corer; Quartz; Sediment type; Size fraction 〈 0.002 mm, clay; Size fraction 0.004-0.002 mm, 8.0-9.0 phi, very fine silt; Size fraction 0.008-0.004 mm, 7.0-8.0 phi, fine silt; Size fraction 0.016-0.008 mm, 6.0-7.0 phi, medium silt; Size fraction 0.032-0.016 mm, 5.0-6.0 phi, coarse silt; Size fraction 0.063-0.032 mm, 4.0-5.0 phi, very coarse silt; Size fraction 0.125-0.063 mm, 3.0-4.0 phi, very fine sand; Size fraction 0.250-0.125 mm, 2.0-3.0 phi, fine sand; Size fraction 0.500-0.250 mm, 1.0-2.0 phi, medium sand; Size fraction 1.000-0.500 mm, 0.0-1.0 phi, coarse sand; Size fraction 2.000-1.000 mm, (-1.0)-0.0 phi, very coarse sand
    Type: Dataset
    Format: text/tab-separated-values, 1308 data points
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