skip to main content


Title: Retreat of the Smith Sound Ice Stream in the Early Holocene

Nares Strait, a major connection between the Arctic Ocean and Baffin Bay, was blocked by coalescent Innuitian and Greenland ice sheets during the last glaciation. This paper focuses on the events and processes leading to the opening of the strait and the environmental response to establishment of the Arctic‐Atlantic throughflow. The study is based on sedimentological, mineralogical and foraminiferal analyses of radiocarbon‐dated cores 2001LSSL‐0014PCandTCfrom northern Baffin Bay. Radiocarbon dates on benthic foraminifera were calibrated with ΔR = 220±20 years. Basal compact pebbly mud is interpreted as a subglacial deposit formed by glacial overriding of unconsolidated marine sediments. It is overlain by ice‐proximal (red/grey laminated, ice‐proximal glaciomarine unit barren of foraminifera and containing >2 mm clasts interpreted as ice‐rafted debris) to ice‐distal (calcareous, grey pebbly mud with foraminifera indicative of a stratified water column with chilled Atlantic Water fauna and species associated with perennial and then seasonal sea ice cover) glacial marine sediment units. The age model indicates ice retreat into Smith Sound as early asc. 11.7 and as late asc. 11.2 cal. kaBPfollowed by progressively more distal glaciomarine conditions as the ice margin retreated toward the Kennedy Channel. We hypothesize that a distinctIRDlayer deposited between 9.3 and 9 (9.4–8.9 1σ) cal. kaBPmarks the break‐up of ice in Kennedy Channel resulting in the opening of Nares Strait as an Arctic‐Atlantic throughflow. Overlying foraminiferal assemblages indicate enhanced marine productivity consistent with entry of nutrient‐rich Arctic Surface Water. A pronounced rise in agglutinated foraminifers and sand‐sized diatoms, and loss of detrital calcite characterize the uppermost bioturbated mud, which was deposited after 4.8 (3.67–5.55 1σ) cal. kaBP. The timing of the transition is poorly resolved as it coincides with the slow sedimentation rates that ensued after the ice margins retreated onto land.

 
more » « less
Award ID(s):
1804504
NSF-PAR ID:
10371282
Author(s) / Creator(s):
 ;  ;  ;  ;  
Publisher / Repository:
Wiley-Blackwell
Date Published:
Journal Name:
Boreas
Volume:
48
Issue:
4
ISSN:
0300-9483
Page Range / eLocation ID:
p. 825-840
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. In order to document changes in Holocene glacier extent and activity inNEGreenland (~73° N) we study marine sediment records that extend from the fjords (PS2631 andPS2640), across the shelf (PS2623 andPS2641), to the Greenland Sea (JM07‐174GC). The primary bedrock geology of the source areas is the Caledonian sediment outcrop, including Devonian red beds, plus early Neoproterozoic gneisses and early Tertiary volcanics. We examine the variations in colour (CIE*), grain size, and bulk mineralogy (from X‐ray diffraction of the <2 mm sediment fraction). Fjord corePS2640 in Sofia Sund, with a marked red hue, is distinct in grain size, colour and mineralogy from the other fjord and shelf cores. Five distinct grain‐size modes are distinguished of which only one is associated with a coarse ice‐rafting signal – this mode is rare in the mid‐ and late Holocene. A sediment unmixing program (SedUnMixMC) is used to characterize down‐core changes in sediment composition based on the upper late Holocene sediments from coresPS2640 (Sofia Sund),PS2631 (Kaiser Franz Joseph Fjord) andPS2623 (south of Shannon Is), and surface samples from the Kara Sea (as an indicator of transport from the Russian Arctic shelves). Major changes in mineral composition are noted in all cores with possible coeval shifts centredc. 2.5, 4.5 and 7.5 cal. kaBP(±0.5 ka) but are rarely linked with changes in the grain‐size spectra. CoarseIRD(>2 mm) andIRD‐grain‐size spectra are rare in the last 9–10 cal. kaBPand, in contrast with areas farther south (~68° N), there is no distinctIRDsignal at the onset of neoglaciation. Our paper demonstrates the importance of the quantitative analysis of sediment properties in clarifying source to sink changes in glacial marine environments.

     
    more » « less
  2. Palaeomagnetic investigation of three sediment cores from the Chukchi and Beaufort Sea margins was performed to better constrain the regional chronostratigraphy and to gain insights into sediment magnetic properties at the North American Arctic margin during the Holocene and the preceding deglaciation. Palaeomagnetic analyses reveal that the sediments under study are characterized by low‐coercivity ferrimagnetic minerals (magnetite), mostly in the pseudo‐single domain grain‐size range, and by a strong, stable, well‐defined remanent magnetization (MAD<5°). Age models for these sediment cores were constrained by comparing their palaeomagnetic secular variations (inclination, declination and relative palaeointensity) with previously published and independently dated sedimentary marine records from the study area. The magnetostratigraphical age models were verified byAMSradiocarbon dating tie points, tephrochronology and210Pb‐based sedimentation rate estimate. The analysed cores 01JPC, 03PCand 02PCspanc. 6000, 10 500 and 13 500 cal. aBP, respectively. The estimated sedimentation rates were stable and relatively high since the deglaciation in cores 01JPC(60 cm ka−1) and 03PC(40–70 cm ka−1). Core 02PCshows much lower Holocene sedimentation rates with a strong decrease after the deglaciation from ~60 to 10–20 cm ka−1. Overall, this study illustrates the usefulness of palaeomagnetism to improve the dating of late Quaternary sedimentary records in the Arctic Ocean.

     
    more » « less
  3. ABSTRACT A new calcareous Arctic foraminiferal species, Glomulina oculus n. sp., belonging to the suborder Miliolina has been observed in surface samples from northern Nares Strait and Petermann Fjord, NW Greenland, and off Zachariae Isbrae, NE Greenland, as well as in early Holocene sediments from the northern Baffin Bay region and on the NE Greenland shelf. In some samples, this new porcelaneous species makes up a significant fraction of the foraminiferal assemblage, particularly in samples with a relatively large sand content, and we suggest that this species is indicative of an Arctic environment with marine-terminating glaciers. Yet, further studies are needed to ascertain its full habitat range. 
    more » « less
  4. Background

    Dysregulation of the corticotropin‐releasing factor (CRF) system has been observed in rodent models of binge drinking, with a large focus onCRFreceptor 1 (CRF‐R1). The role ofCRF‐binding protein (CRFBP), a key regulator ofCRFactivity, in binge drinking is less well understood. In humans, single‐nucleotide polymorphisms inCRHBPare associated with alcohol use disorder and stress‐induced alcohol craving, suggesting a role forCRFBPin vulnerability to alcohol addiction.

    Methods

    The role and regulation ofCRFBPin binge drinking were examined in mice exposed to the drinking in the dark (DID) paradigm. Using in situ hybridization, the regulation ofCRFBP,CRF‐R1, andCRFmRNAexpression was determined in the stress and reward systems of C57BL/6J mice after repeated cycles ofDID. To determine the functional role ofCRFBPin binge drinking,CRFBPknockout (CRFBP KO) mice were exposed to 6 cycles ofDID, during which alcohol consumption was measured and compared to wild‐type mice.

    Results

    CRFBPmRNAexpression was significantly decreased in the prelimbic (PL) and infralimbic medial prefrontal cortex (mPFC) of C57BL/6J mice after 3 cycles and in thePLmPFCafter 6 cycles ofDID. No significant changes inCRForCRF‐R1 mRNAlevels were observed in mPFC, ventral tegmental area, bed nucleus of the stria terminalis, or amygdala after 3 cycles ofDID.CRFBP KOmice do not show significant alterations in drinking compared to wild‐type mice across 6 cycles of DID.

    Conclusions

    These results reveal that repeated cycles of binge drinking alterCRFBPmRNAexpression in the mPFC, a region responsible for executive function and regulation of emotion and behavior, including responses to stress. We observed a persistent decrease inCRFBPmRNAexpression in the mPFCafter 3 and 6DIDcycles, which may allow for increasedCRFsignaling atCRF‐R1 and contribute to excessive binge‐like ethanol consumption.

     
    more » « less
  5. Lake El'gygytgyn, located in central Chukotka, Russian Arctic, was the subject of an international drilling project that resulted in the recovery of the longest continuous palaeoclimatic and palaeoenvironmental record for the terrestrial Arctic covering the last 3.6 million years. Here, we present the reconstruction of the lake‐level fluctuations of Lake El'gygytgyn since Marine Isotope Stage (MIS) 7 based on lithological and palynological as well as chronological studies of shallow‐water sediment cores and subaerial lake terraces. Reconstructed lake levels show an abrupt rise during glacial–interglacial terminations (MIS6/5 andMIS2/1) and during theMIS4/3 stadial–interstadial transition. The most prominent lowstands occurred during glacial periods associated with a permanent lake‐ice cover (namelyMIS6,MIS4 andMIS2). Major triggering mechanisms of the lake‐level fluctuations at Lake El'gygytgyn are predominantly changes in air temperature and precipitation. Regional summer temperatures control the volume of meltwater supply as well as the duration of the lake‐ice cover (permanent or seasonal). The duration of the lake‐ice cover, in turn, enables or hampers near‐shore sediment transport, thus leading to long‐term lake‐level oscillations on glacial–interglacial time scales by blocking or opening the lake outflow, respectively. During periods of seasonal ice cover the lake level was additionally influenced by changes in precipitation. The discovered mechanism of climatologically driven level fluctuations of Lake El'gygytgyn are probably valid for large hydrologically open lakes in the Arctic in general, thus helping to understand arctic palaeohydrology and providing missing information for climate modelling.

     
    more » « less