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  • Weitere Quellen  (12)
  • 1
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    Linking the 8.2 ka Event and its Freshwater Forcing in the Labrador Sea (2012)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The 8.2 ka event was the last deglacial abrupt climate event. A reduction in the Atlantic meridional overturning circulation (AMOC) attributed to the drainage of glacial Lake Agassiz may have caused the event, but the freshwater signature of Lake Agassiz discharge has yet to be identified in (delta)18O of foraminiferal calcite records from the Labrador Sea, calling into question the connection between freshwater discharge to the North Atlantic and AMOC strength. Using Mg/Ca-paleothermometry, we demonstrate that approx. 3 C of near-surface ocean cooling masked an 1.0 % decrease in western Labrador Sea (delta)18O of seawater concurrent with Lake Agassiz drainage. Comparison with North Atlantic (delta)18O of seawater records shows that the freshwater discharge was transported to regions of deep-water formation where it could perturb AMOC and force the 8.2 ka event.
    Schlagwort(e): Oceanography
    Materialart: GSFC-E-DAA-TN8981 , Geophysical Research Letters; 39; 10; L18703; L18703
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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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
    Publikationsdatum: 2017-04-06
    Beschreibung: 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.
    Materialart: Article , PeerReviewed
    Format: text
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    ARTIKEL (OCEANREP)
  • 3
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    Variations in the provenance of sediment from ice sheets surrounding Baffin Bay during MIS 2 and 3 and export to the Labrador Shelf Sea: site HU2008029-0008 Davis Strait (2013)
    Wiley
    In:  Journal of Quaternary Science, 29 (1). pp. 3-13.
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    Publikationsdatum: 2020-07-20
    Beschreibung: Based on quantitative X-ray diffraction mineralogical analysis of cores HU2008029-0006/0008 (857-m water depth) located south of the Davis Strait sill, we seek answers to two questions: (i) the temporal correlation of NW Labrador Shelf Sea Heinrich (H-) and Baffin Bay detrital carbonate (BBDC) events, and (ii) the provenance of the sediments? A sediment-unmixing model (SedUnMix) is used to determine provenance variations. Although 12 radiocarbon dates were obtained there were many age reversals and we favour a depth/age model for HU2008029-0008PC based on correlations to well-dated neighbouring cores north and south of Davis Strait. We find no correlation between H- and BBDC events except for H-0, which appears to be a broadly synchronous event along the NE Canadian margin and is correlative with an episode of major moraine building along this flank of the Laurentide Ice Sheet. Unmixing of the sediment composition based on six potential glacial source regions indicates that the bulk of the sediment in 0008PC is derived from glacial erosion of West Greenland, but is punctuated by intervals when dolomite-rich sediments, derived from outcrops north of Baffin Bay, dominate the composition. Estimated dates on these BBDC events are -13, 25 and 30–38 cal ka BP.
    Materialart: Article , PeerReviewed
    Format: text
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    ARTIKEL (OCEANREP)
  • 4
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    Interaction between warm Atlantic-sourced waters and the East Greenland Current in northern Denmark Strait (68°N) during the last 10 600 cal a BP (2016)
    Wiley
    In:  Journal of Quaternary Science, 31 (5). pp. 472-483.
    Details
    Publikationsdatum: 2020-07-20
    Beschreibung: Changes in the Holocene interaction of the (i) cold/fresh East Greenland Current (EGC) and (ii) warm/saline Irminger Current (IC) in northern Denmark Strait have been reconstructed from benthic and planktic foraminifera assemblages, ice-rafted debris, grain-size analyses and quantitative X-ray diffraction. During the time from c. 10 600 to 8000 cal a BP, palaeoceanographic reconstructions reveal waning deglacial influence from the receding Greenland Ice Sheet and presence of a strong EGC caused low surface water productivity. From c. 8000 cal a BP, a predominant influence of Atlantic-sourced IC waters on subsurface water conditions became established in northern Denmark Strait, which accompanied low surface water productivity. Relatively warm surface and subsurface water conditions, i.e. reduced EGC and strong IC influence, are found from c. 6500 to 4500 cal a BP, representing Holocene optimum-like conditions. A mid- to late Holocene EGC strengthening caused increased stratification and formation of a distinct halocline. However, we recognize millennial-scale periods of reduced stratification by an enhanced influence of Atlantic-sourced IC Water on surface water conditions: (i) at c. 2500–1400 cal a BP the time of the Roman Warm Period and (ii) at c. 300 cal a BP the later part of the Little Ice Age. These periods of oceanic warming probably relate to changes in the Subpolar Gyre dynamics that led to enhanced entrainment of Atlantic-sourced IC Water into northern Denmark Strait.
    Materialart: Article , PeerReviewed
    Format: text
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    ARTIKEL (OCEANREP)
  • 5
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    Glaciers, Oceans, Atmosphere and Climate (2006)
    Blackwell
    In:  In: Glacier Science and Environmental Change. , ed. by Knight, P. G. Blackwell, Malden, Mass., pp. 95-113.
    Details
    Publikationsdatum: 2018-01-31
    Materialart: Book chapter , NonPeerReviewed
    Format: text
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    ARTIKEL (OCEANREP)
  • 6
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    Late Quaternary marine sediment accumulation in fiord-shelf-deep-sea transects, Baffin Island to Baffin Bay (1987)
    Elsevier
    In:  Quaternary Science Reviews, 6 (3-4). pp. 231-243.
    Details
    Publikationsdatum: 2016-04-08
    Beschreibung: Piston cores from fiords, shelf troughs, and the deep-sea off eastern Baffin Island, N.W.T., Canada, have been sampled for texture and detrital carbonate in the 〈2 mm fraction. The sediments consist primarily of silty clays usually containing 〈5% sand. Estimates are made for sediment accumulation (kg/m**2/ka) over the last ca. 10 ka. Three sets, of two cores each, lie on a fiord-shelf transect and thus define variations in sediment accumulation gradients. These continental margin data are compared with cruder estimates of Holocene sediment accumulation at three sites farther offshore in Baffin Bay, Davis Strait and the northern Labrador Sea. Minimum accumulation in a 2 ka interval was 200 kg/m2 with a maximum estimate of 8,800 kg/m2. Detrital carbonate accumulation varies between 0 and 1,300 kg/m**2. Median accumulation for a typical fiord-shelf-deep-sea transect over the last 10 ka have been 10,340, 3493 and 820 kg/m**2. At DSDP Leg, site 645 in central Baffin Bay, the sedimentation rate ranged between 40 and 130 m/Ma (ca. 400 and 1200 kg/m**2/2ka); that is, comparable with the Late Quaternary input into Baffin Bay.
    Materialart: Article , PeerReviewed
    Format: text
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    ARTIKEL (OCEANREP)
  • 7
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    Late Quaternary (Stage 2 and 3) Meltwater and Heinrich Events, Northwest Labrador Sea (1994)
    Elsevier
    In:  Quaternary Research, 41 (1). pp. 26-34.
    Details
    Publikationsdatum: 2016-04-08
    Beschreibung: 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.
    Materialart: Article , PeerReviewed
    Format: text
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  • 8
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    Fiord to Deep Sea Sediment Transfers along the Northeastern Canadian Continental Margin: Models and Data (1990)
    Presses de l'Université de Montréal
    In:  Géographie Physique et Quaternaire, 44 (1). pp. 55-70.
    Details
    Publikationsdatum: 2020-07-30
    Beschreibung: In Alaskan fiords, sedimentation rates are high; during a glacial advance fiord-basin sediments are transported to the ice front to form a shoal which reduces the calving rate. Thus, during successive glacial cycles, sediment is initially stored and then removed from fiord basins. In the fiords of eastern Baffin Island sedimentation rates are, and were, much lower (〈 1000 Kg/m2 ka). and fiord-basin fills may span several glacial cycles. This hypothesis is in keeping with the relatively low sedimentation rates on the adjacent shelf (50 to 500 kg/m2 ka) and deep-sea plain (〈 = 50 kg/m2 ka). The advance of outlet glaciers through these arctic fiords may be explained by the in situ growth of a floating ice-shelf, grounded at the mouth of the fiord. The extent of late Foxe Glaciation in McBeth and ltirbilung fiords can be delimited by raised marine deltas (50-85 m asl) with 14C dates on in situ shells and whalebone of 〉54 ka. Holocene raised beaches are lower and date 〈10 ka. These data, plus the absence of tills in raised marine sections along the outer coast, make it difficult to extend grounded ice onto the shelf during the 18 ka global maximum. Piston cores from Tingin. ltirbilung and McBeth fiords vary between 4 and 11 m in length, but only sample a proportion of the total basin-fills.
    Materialart: Article , PeerReviewed
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  • 9
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    Late quaternary spatial and temporal changes in clay- and silt-size mineral assemblages of fiord and shelf cores, western Baffin Bay, northwest North Atlantic (1989)
    Elsevier
    In:  Continental Shelf Research, 9 (5). pp. 445-463.
    Details
    Publikationsdatum: 2016-04-08
    Beschreibung: 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.
    Materialart: Article , PeerReviewed
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  • 10
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    Temporal changes in Holocene δ18O records from the northwest and central North Iceland Shelf (2004)
    Wiley
    In:  Journal of Quaternary Science, 19 (4). pp. 321-334.
    Details
    Publikationsdatum: 2020-07-20
    Beschreibung: The region of north Iceland is highly sensitive climatically owing to its location with respect to atmospheric and oceanographic fronts. In this study we present total carbonate and δ18O records of benthic and planktic Foraminifera from nine sediment cores from the North Iceland Shelf. The results of this work indicate that the deglaciation of the Vestfirdir Peninsula was completed by 10 200 cal. yr BP. The 8200 cal. yr BP cold event is present only as a minor isotopic event, and seems not to have had much of a cooling effect on the bottom waters of the northwest Iceland shelf. The Holocene maximum warmth, attributed to a stronger North Icelandic Irminger Current, occurred between ca. 7800 and 6200 cal. yr BP. Over the past 4500 cal. yr BP a general cooling trend has occurred on the North Iceland Shelf, and superimposed on this overall cooling trend are a number of oscillations between periods when relatively warmer and cooler waters occupied the shelf. Relatively cooler waters were present at 4200–4000 cal. yr BP, 3200–2900 cal. yr BP, 2500–2350 cal. yr BP and 600–200 cal. yr BP, whereas relatively warmer waters were present on the shelf at 3750–3450 cal. yr BP, 2800–2600 cal. yr BP and 1700–1000 cal. yr BP.
    Materialart: Article , PeerReviewed
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