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  • 1
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    Polar Soils - John C. F. Tedrow Soils of the polar landscapes. New Brunswick, New Jersey, Rutgers University Press, xxvi, 638 p, illus. $60. (1977)
    Cambridge University Press
    Details
    Publication Date: 1977-09-01
    Print ISSN: 0032-2474
    Electronic ISSN: 1475-3057
    Topics: Ethnic Sciences , Geography
    Published by Cambridge University Press
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  • 2
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    Eigenvector Analysis of Reconstructed Holocene July Temperature Departures over Northern Canada (1981)
    Cambridge University Press
    Details
    Publication Date: 1981-11-01
    Description: July temperatures for the past 6000 yr at 11 sites in northern Canada have been predicted by transfer-function equations. Normalized departures from the mean of each time series at 250-yr intervals are analyzed by principal component (eigenvector) analysis. An initial analysis included 9 sites and the first three principal components accounted for 85.7% of the variance. Maps of the loadings on the principal components show broad spatial coherence on all three components. Temporal coefficients (principal component scores) illustrate major regional and local midsummer temperature variations. An additional 2 sites were then included but the spatial pattern of the loadings remained essentially unchanged. A further test of this approach, with a view toward predicting paleoclimates of northern regions, was to use the spatial coefficients (loadings) to estimate the July temperature departures at an “unknown” site (Long Lake, Keewatin). This reconstruction compares favorably with an independent transfer-function reconstruction (Kay, 1979). Power spectrum analysis of the significant principal component scores (temperature departures) over the 6000 yr showed that the temporal fluctuations associated with the first three principal components follow a “red noise” spectrum, indicative of strong persistence in the reconstructed climatic records. The scores on the fourth principal component approximate a “white noise” spectrum. A peak in power between 2000 and 3000 yr occurs in the variance spectrum of the second principal component (significance 10%). We conclude that eigenvector analysis of Holocene paleoclimatic data has considerable power and may be useful for identifying regional and local climatic variations.
    Print ISSN: 0033-5894
    Electronic ISSN: 1096-0287
    Topics: Geography , Geosciences
    Published by Cambridge University Press
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  • 3
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    Problems and Possible Solutions Concerning Radiocarbon Dating of Surface Marine Sediments, Ross Sea, Antarctica (1999)
    Cambridge University Press
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    Publication Date: 1999-09-01
    Description: Radiocarbon accelerator mass spectrometric (AMS) dates on the acid-insoluble fraction from 38 core tops from the western Ross Sea, Antarctica, are used to address these questions: (1) What are the apparent ages of sediments at or close to the present sediment/water interface? (2) Is there a statistically significant pattern to the spatial distribution of core top ages? and (3) Is there a “correction factor” that can be applied to these age determinations to obtain the best possible Holocene (downcore) chronologies? Ages of core top sediments range from 2000 to 21,000 14C yr B.P. Some “old” core top dates are from piston cores and probably represent the loss of sediment during the coring process, but some core top samples 〉6000 14C yr B.P. may represent little or no Holocene deposition. Four possible sources of variability in dates ≤6000 14C yr B.P. (n = 28) are associated with (1) different sample preparation methods, (2) different sediment recovery systems, (3) different geographic regions, and (4) within-sample lateral age variability. Statistical analysis on an a posteriori design indicates that geographic area is the major cause of variability; there is a difference in mean surface sediment age of nearly 2000 yr between sites in the western Ross Sea and sites east of Ross Bank in south-central Ross Sea. The systematic variability in surface age between areas may be attributed to: (a) variable sediment accumulation rates (SAR) (surface age is inversely related to SAR), (b) differences in the percentage of reworked (dead) carbon between each area, and/or (c) differences in the CO2 exchange between the ocean and the atmosphere.
    Print ISSN: 0033-5894
    Electronic ISSN: 1096-0287
    Topics: Geography , Geosciences
    Published by Cambridge University Press
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  • 4
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    Subglacially precipitated carbonates record geochemical interactions and pollen preservation at the base of the Laurentide Ice Sheet on central Baffin Island, eastern Canadian Arctic (2014)
    Cambridge University Press
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    Publication Date: 2014-01-01
    Description: The mineralogy and isotopic compositions of subglacially precipitated carbonate crusts (SPCCs) provide information on conditions and processes beneath former glaciers and ice sheets. Here we describe SPCCs formed on gneissic bedrock at the bed of the Laurentide Ice Sheet (LIS) during the last glacial maximum on central Baffin Island. Geochemical data indicate that the Ca in the crusts was likely derived from the subglacial chemical weathering Ca-bearing minerals in the local bedrock. C and Sr isotopic analyses reveal that the C in the calcite was derived predominantly from older plant debris. The δ18O values of the SPCCs suggest that these crusts formed in isotopic equilibrium with basal ice LIS preserved in the Barnes Ice Cap (BIC). Columnar crystal fabric and the predominance of sparite over micrite in the SPCCs are indicative of carbonate precipitation under open-system conditions. However, the mean δ18O value of the calcite crusts is ~ 10‰ higher than those of primary LIS ice preserved in the BIC, demonstrating that SPCCs record the isotopic composition of only basal ice. Palynomorph assemblages preserved within the calcite and basal BIC ice include species last endemic to the Arctic in the early Tertiary. The source of these palynomorphs remains enigmatic.
    Print ISSN: 0033-5894
    Electronic ISSN: 1096-0287
    Topics: Geography , Geosciences
    Published by Cambridge University Press
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  • 5
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    Early to mid-Holocene Atlantic water influx and deglacial meltwater events, Beaufort Sea Slope, Arctic Ocean (2004)
    Cambridge University Press
    Details
    Publication Date: 2004-01-01
    Description: Holocene high-resolution cores from the margin of the Arctic Ocean are rare. Core P189AR-P45 collected in 405-m water depth on the Beaufort Sea slope, west of the Mackenzie River delta (70°33.03′N and 141°52.08′W), is in close vertical proximity to the present-day upper limit of modified Atlantic water. The 5.11-m core spans the interval between ∼6800 and 10,400 14C yr B.P. (with an 800-yr ocean reservoir correction). The sediment is primarily silty clay with an average grain-size of 9 φ. The chronology is constrained by seven radiocarbon dates. The rate of sediment accumulation averaged 1.35 mm/yr. Stable isotopic data (δ18O and δ13C) were obtained on the polar planktonic foraminifera Neogloboquadrina pachyderma (s) and the benthic infaunal species Cassidulina neoteretis. A distinct low-δ18O event is captured in both the benthic and planktonic data at ∼10,000 14C yr B.P.—probably recording the glacial Lake Agassiz outburst flood associated with the North Atlantic preboreal cold event. The benthic foraminifera are dominated in the earliest Holocene by C. neoteretis, a species associated with modified Atlantic water masses. This species decreases toward the core top with a marked environmental reversal occurring ∼7800 14C yr B.P. possibly coincident with the northern hemisphere 8200 cal yr B.P. cold event.
    Print ISSN: 0033-5894
    Electronic ISSN: 1096-0287
    Topics: Geography , Geosciences
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  • 6
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    Late Quaternary (Stage 2 and 3) Meltwater and Heinrich Events, Northwest Labrador Sea (1994)
    Cambridge University Press
    Details
    Publication Date: 1994-01-01
    Description: Two major meltwater events are documented in cores from the NW Labrador Sea. One occurred ca. 20,000 14C yr B.P. in association with deposition of a major detrital carbonate unit. Both prior to and after this event, δ18O values of near-surface planktonic foraminifera were 4.5%, indicating fully enriched glacial values. A younger event (ca. 14,000 14 C yr B.P.) is characterized by a dramatic change in δ18O from 4.5 to 2.0% and coincided with the retreat of ice from the outer SE Baffin Shelf, possibly into Hudson Strait. These meltwater events coincide with Heinrich (H) layers 1 and 2 from North Atlantic sediments. The 14,000 14C yr B.P. meltwater event indicates that the eastern margin of the Laurentide Ice Sheet also underwent rapid retreat at approximately the same time as other ice sheet margins around the NE North Atlantic. A third major detrital carbonate event at the base of HU87-033-009, possibly correlative with Heinrich layer 3, occurred ca. 33,960 ± 675 14 C yr B.P.; however, this is older than the accepted date for H-3 of 27,000 14C yr B.P. and may be H-4.
    Print ISSN: 0033-5894
    Electronic ISSN: 1096-0287
    Topics: Geography , Geosciences
    Published by Cambridge University Press
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  • 7
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    Cooling and freshening at 8.2 ka on the NW Iceland Shelf recorded in paired δ18O and Mg/Ca measurements of the benthic foraminifer Cibicides lobatulus (2012)
    Cambridge University Press
    Details
    Publication Date: 2012-09-04
    Description: A shallow marine sediment core from NW Iceland provides evidence for a brief cooling and freshening at ~ 8200 cal yr BP, consistent with the hypothesis that the catastrophic outburst flood of the proglacial lakes Oijbway and Agassiz caused the 8.2 ka event. This is the first high-resolution record reconstructing near-surface temperatures and δ18Osw by paired measurements of Mg/Ca and δ18Ocalcite of a benthic foraminifer. We developed a new Mg/Ca temperature calibration for Cibicides lobatulus. Our down-core Mg/Ca derived temperature reconstruction dates the 8.2 ka cooling event between ~ 8300 cal yr BP and ~ 8100 cal yr BP, which is similar to the timing and 160-yr duration recorded in the Greenland ice cores. The near-surface temperature drop of ~ 3 to 5°C during the 8.2 ka event was accompanied by lighter δ18Osw values. Synchronously to the changes in the geochemical proxies, the percentages of two Arctic benthic foraminifers increased and the percent calcium carbonate decreased. Our record, combined with several others from the region, suggests that the freshwater outburst spread far from the source into the high-latitude North Atlantic. This freshwater input could have directly caused substantial high-latitude cooling, with reduced North Atlantic Deep Water formation amplifying the climatic impact.
    Print ISSN: 0033-5894
    Electronic ISSN: 1096-0287
    Topics: Geography , Geosciences
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  • 8
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    Circum-Antarctic coastal environmental shifts during the Late Quaternary reflected by emerged marine deposits (1998)
    Cambridge University Press
    Details
    Publication Date: 1998-09-01
    Description: This review assesses the circumpolar occurrence of emerged marine macrofossils and sediments from Antarctic coastal areas in relation to Late Quaternary climate changes. Radiocarbon ages of the macrofossils, which are interpreted in view of the complexities of the Antarctic marine radiocarbon reservoir and resolution of this dating technique, show a bimodal distribution. The data indicate that marine species inhabited coastal environments from at least 35 000 to 20 000 yr BP, during Marine Isotope Stage 3 when extensive iceberg calving created a ‘meltwater lid’ over the Southern Ocean. The general absence of these marine species from 20 000 to 8500 yr BP coincides with the subsequent advance of the Antarctic ice sheets during the Last Glacial Maximum. Synchronous re-appearance of the Antarctic marine fossils in emerged beaches around the continent, all of which have Holocene marine-limit elevations an order of magnitude lower than those in the Arctic, reflect minimal isostatic rebound as relative sea-level rise decelerated. Antarctic coastal marine habitat changes around the continent also coincided with increasing sea-ice extent and outlet glacial advances during the mid-Holocene. In view of the diverse environmental changes that occurred around the Earth during this period, it is suggested that Antarctic coastal areas were responding to a mid-Holocene climatic shift associated with the hydrological cycle. This synthesis of Late Quaternary emerged marine deposits demonstrates the application of evaluating circum-Antarctic phenomena from the glacial-terrestrial-marine transition zone.
    Print ISSN: 0954-1020
    Electronic ISSN: 1365-2079
    Topics: Biology , Geography , Geosciences
    Published by Cambridge University Press
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  • 9
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    The role of the Iceland Ice Sheet in the North Atlantic during the late Quaternary: a review and evidence from Denmark Strait (2008)
    Wiley-Blackwell
    In:  Journal of Quaternary Science, 23 (1). pp. 3-20.
    Details
    Publication Date: 2017-04-06
    Description: Investigations indicate that the Iceland Ice Sheet was reduced in size during MIS 3 but readvanced to the shelf break at the LGM. Retreat occurred very rapidly around 15 k–16 k cal. yr BP. By contrast, the margin of the ice sheet on the East Greenland shelf, north of the Denmark Strait, was at or close to the shelf break during MIS 3 and 2 and retreat starting ∼17 k cal. yr BP. Quantitative X-ray diffraction analysis of the 〈2 mm sediment fraction was undertaken on 161 samples from Iceland and East Greenland diamictons, and from cores on the slopes and margins of the Denmark Strait. Weight% mineralogical data are used in a principal component analysis to differentiate sediments derived from the two margins. The first two PC axes explain 52% of the variance. These associations are used to characterise sediments as being affiliated with (a) Iceland, (b) East Greenland or (c) mixed. The contribution from Iceland becomes prominent during MIS 2. The extensive outcrop of early Tertiary basalts on East Greenland between 68° and 71° N is an alternative source for basaltic clasts and North Atlantic sediments with εNd(0) values close to ±0.
    Type: Article , PeerReviewed
    Format: text
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  • 10
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    Seeking a Holocene drift ice proxy: non-clay mineral variations from the SW to N-central Iceland shelf: trends, regime shifts, and periodicities (2009)
    Wiley-Blackwell
    In:  Journal of Quaternary Science, 24 (7). pp. 664-676.
    Details
    Publication Date: 2016-06-29
    Description: Quantitative X-ray diffraction analysis of the 〈2mm sediment fraction was carried out on 1257 samples (from the seafloor and 16 cores) from the Iceland shelf west of 188 W. All but one core (B997-347PC) were from transects along troughs on theNW to N-central shelf, an area that in modern and historic times has been affected by drift ice. The paper focuses on the non-clay mineralogy of the sediments (excluding calcite and volcanic glass). Quartz and potassium feldspars occupy similar positions in an R-mode principal component analysis, and oligoclase feldspar tracks quartz; these minerals are used as a proxy for ice-rafted detritus (IRD). Accordingly, the sum of these largely foreign minerals (Q&K) (to Icelandic bedrock) is used as a proxy for drift ice. A stacked, equi-spaced 100 a record is developed which shows both low-frequency trends and higher-frequency events. The detrended stacked record compares well with the flux of quartz (mg cm-2 a-1) at MD99-2269 off N Iceland. The multi-taper method indicated that there are three significant frequencies at the 95% confidence level with periods of ca. 2500, 445 and 304 a. Regime shift analysis pinpoints intervals when there was a statistically significant shift in the average Q&K weight %, and identifies four IRDrich events separated by intervals with lower inputs. There is some association between peaks of IRD input, less dense surface waters (from d18O data on planktonic foraminifera) and intervals of moraine building.
    Type: Article , PeerReviewed
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