Geomorphic and sedimentary signatures of early Holocene deglaciation in High Arctic fiords, Ellesmere Island, Canada: implications for deglacial ice dynamics and thermal regime

1998 ◽  
Vol 35 (4) ◽  
pp. 437-452 ◽  
Author(s):  
Colm Ó Cofaigh
Keyword(s):  
Thermal Regime ◽  
High Arctic ◽  
Ellesmere Island ◽  
Early Holocene ◽  
Ice Dynamics ◽  
Discrete Location ◽  
Radiocarbon Dates ◽  
Fine Grained ◽  
Subsequent Stabilization

Integrated studies of glacial geomorphology, sedimentology, marine-limit elevations, and radiocarbon dating in two adjacent fiords on southwestern Ellesmere Island indicate that early Holocene regional deglaciation was characterized by a two-step retreat pattern, where initial rapid breakup of marine-based ice preceded slower, terrestrial retreat. These data also indicate interfiord variations in early Holocene deglacial thermal regime, and illustrate the role of fiord topography as a control on glacier retreat. In Starfish Bay, deglacial landform-sediment associations are preferentially located at fiord-side topographic irregularities, and record ice-proximal glaciomarine sedimentation during stillstands at pinning points. Abundant fine-grained subaquatic outwash indicates that the retreating trunk glacier was characterized by a warm-based thermal regime. The discrete location of these deposits and associated radiocarbon dates suggest rapid early Holocene deglaciation of the outer and middle fiord, interrupted by brief stillstands at pinning points, and subsequent stabilization and slower retreat in the inner fiord. Similar rapid early Holocene deglaciation occurred in Blind Fiord. However, the dominance of lateral meltwater channels and lack of fine-grained subaquatic outwash in this fiord suggest that trunk ice was predominantly cold-based during retreat. Initial rapid deglaciation was succeeded by stabilization and slower, terrestrial retreat when the trunk glacier reached the inner fiord. A prominent belt of glaciogenic landforms at the heads of both fiords is inferred to mark this stabilization.

scholarly journals Glacial landform-sediment assemblages in the Canadian High Arctic and their implications for late Quaternary glaciations

1999 ◽  
Vol 28 ◽  
pp. 195-201 ◽  
Author(s):  
C. Ó Cofaigh ◽  
D.S. Lemman ◽  
D.J.A. Evans ◽  
J. Bednarski
Keyword(s):  
Thermal Regime ◽  
Late Quaternary ◽  
Thermal Conditions ◽  
High Arctic ◽  
Early Holocene ◽  
Canadian High Arctic ◽  
Fine Grained ◽  
Quaternary Glaciation ◽  
The Last Glacial Maximum ◽  
The Last Glacial

AbstractModern terrestrial glaciers in the Canadian High Arctic range from polythermal to cold-based. Where polythermal glaciers override thick unconsolidated sediment, longitudinal compression and glaciotectonic thrusting produce thrust-block moraines. In contrast, the dominant geomorphic record of cold-based glaciers consists of lateral and proglacial meltwater channels. Geomorphic and sedimentary evidence indicates that late Quaternary fiord glaciers were also characterized by variations in basal thermal regime. Erratic dispersal trains and striated bedrock record the flow of warm- based ice during the Last Glacial Maximum. Emergent grounding-line fans and morainal banks, deposited during deglaciation, consist of heterogeneous glaciomarine deposits that record well-developed subglacial drainage and high sedimentation rates. However, in other fiords, subaqueous outwash and fine-grained glaciomarine deposits are absent and deglaciation is recorded by lateral meltwater channels graded to raised glaciomarine deltas, suggesting these glaciers were predominantly cold-based during retreat. Regionally, deglacial depocentres are located at pinning points within fiords and a prominent belt of glaciogenic landforms at fiord heads records stabilization of ice margins during early Holocene retreat, rather than the limit of late Quaternary glaciation. Collectively, these observations refute previous reconstructions which inferred a climatically controlled switch from cold- to warm-based thermal conditions in fiord glaciers during early Holocene deglaciation, and indicate that the dominant controls on thermal regime were glaciological.

Glacial geology and Quaternary marine stratigraphy of the Robeson Channel area, northeastern Ellesmere Island, Northwest Territories

1986 ◽  
Vol 23 (7) ◽  
pp. 1001-1012 ◽  
Author(s):  
Michael J. Retelle
Keyword(s):  
Greenland Ice Sheet ◽  
Free Fraction ◽  
High Arctic ◽  
Ellesmere Island ◽  
Major Advance ◽  
Total Acid ◽  
Radiocarbon Dates ◽  
The Holocene ◽  
Acid Hydrolysate ◽  
Field Area

Glacial and marine deposits associated with two phases of glaciation are exposed along a 60 km corridor on Ellesmere Island that borders Robeson Channel. The oldest sediments, tentatively dated at ≥ 70 000 BP, were deposited during a major advance of the northwest Greenland ice sheet across Robeson Channel. During subsequent retreat of this ice mass, glaciomarine sediments containing a High Arctic macro- and microfauna were deposited in the isostatic downwarp on Ellesmere Island. This marine unit was radiocarbon dated at 31 300 ± 900 and > 32 000 BP; mean aIle/Ile ratios are 0.218 ± 0.03 for the free fraction and 0.063 ± 0.011 for the total acid hydrolysate.The last ice advance (late Wisconsin – early Holocene) did not extend into the field area from either interior Ellesmere Island or northwest Greenland. The ice-marginal sea transgressed to the marine limit (~116 m) and overlapped the deposits of the previous maximum Greenland advance. Local plateau ice caps did, however, spill over into one major valley and delayed the establishment of the marine limit in this location. Radiocarbon dates on the Holocene marine limit shorelines indicate initial emergence between 8000 and 8600 BP. A mean aIle/Ile ratio of 0.037 was found for the total acid hydrolysate; aIle was undetectable in the free fraction of the Holocene shells.The Holocene and pre-Holocene glacial and marine chronologies in the Robeson Channel area are similar to chronologies demonstrated from other locations in Arctic regions. Tentative correlations based upon aminostratigraphy suggest that the field area has remained, for the most part, ice free since at least 70 000 BP.

The last glaciation of Marvin Peninsula, northern Ellesmere Island, High Arctic, Canada

1989 ◽  
Vol 26 (12) ◽  
pp. 2578-2590 ◽  
Author(s):  
Donald S. Lemmen
Keyword(s):  
High Arctic ◽  
Ellesmere Island ◽  
North Coast ◽  
Radiocarbon Dates ◽  
The North ◽  
Last Glaciation ◽  
Ice Retreat ◽  
Late Wisconsinan ◽  
Glaciomarine Sediments ◽  
North And South

The limit of the last glaciation on Marvin Peninsula, northernmost Ellesmere Island, is recorded by extensive ice-marginal landforms and early Holocene glaciomarine sediments. While glaciers occupied most valleys on the peninsula, other areas remained ice free, as did most of the adjacent fiords. Beyond the ice limit, sparse erratics and degraded meltwater channels within weathered bedrock are evidence of older, more extensive glaciation(s). Shorelines and marine shells 50 m above the limit of the Holocene sea along the north coast relate to these older glacial events.Thirty-four new radiocarbon dates provide a chronology of ice buildup and retreat. Glaciers reached their limit after 23 ka, and locally as late as 11 ka. This was achieved by both expansion of existing glaciers and accumulation on plateau and lowland sites, which are presently ice free. Late Wisconsinan climate was characterized by cold and extreme aridity. Five dates ranging from 11 to 31 ka BP on subfossil bryophytes suggest that ice-free areas were biologically productive throughout the last glaciation. Ice retreat and postglacial emergence had begun by 9.5 ka and was associated with a marked climatic amelioration. The deglacial chronology confirms a pronounced disparity in the timing of ice retreat on the north and south sides of the Grant Land Mountains.

A GIS Database of Submarine Glacial Landforms and Sediments on High-Arctic Continental Shelves

2021 ◽  
Author(s):  
Katharina Streuff ◽  
Colm Ó Cofaigh
Keyword(s):  
Large Scale ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
High Arctic ◽  
Extensive Literature ◽  
Ice Dynamics ◽  
Radiocarbon Dates ◽  
Continental Shelves ◽  
Glacier Dynamics ◽  
Glacial Landforms

<p>A new digital database compiling glacial landforms and sediments in the High Arctic was created in order to facilitate and underpin new research on palaeo-ice sheets and tidewater glacier dynamics. The database is in a geographic information system (GIS) format and will be available for web download when published. It documents evidence of previous glacial activity as visible on the contemporary seafloor of fjords and continental shelves around all of Svalbard, Greenland, and Alaska, and north of 66°30’ N in Russia, Norway, and Canada. Extensive literature research was conducted to create the database, compiling a large number of glacial landforms at a range of scales, sediment cores, and radiocarbon dates. Glacial landforms included in the database are cross-shelf troughs, trough-mouth fans, grounding-zone wedges, overridden moraines, glacial lineations, drumlins, crag-and-tails, medial moraines, terminal moraines, debris-flow lobes (including glacier-contact fans), recessional moraines, De Geer moraines, crevasse-fill ridges, eskers and submarine channels. Sediment core locations are attributed with a description of the sampled lithofacies and sediment accumulation rates where available. Radiocarbon dates were included when thought to be relevant for constraining the timing of large-scale palaeo-ice dynamics. Outlines of bathymetric datasets published before December 2020 were also mapped to give an overview of previously investigated research areas. The database will aid researchers in the reconstruction of ice dynamics during and since the Last Glacial Maximum and in the interpretation of High-Arctic glacial landform-sediment assemblages. Moreover, apart from providing a comprehensive bibliography on Arctic glacial geomorphological and sedimentological research, it is intended to serve as a basis for future ice sheet modelling of High-Arctic glacier dynamics.</p>

Glacier dynamics and paleoclimatic change during the last glaciation of eastern Ellesmere Island, Canada

1996 ◽  
Vol 33 (5) ◽  
pp. 779-799 ◽  
Author(s):  
John England
Keyword(s):  
Late Quaternary ◽  
Ice Core ◽  
Ice Cores ◽  
High Arctic ◽  
Ellesmere Island ◽  
Canadian High Arctic ◽  
Regional Warming ◽  
Ice Dynamics ◽  
The North ◽  
Glacier Dynamics

A 300 km transect along the east coast of Ellesmere Island fills a major gap in the late Quaternary data base of the Canadian High Arctic. The last glacial maximum (LGM) is marked by prominent moraines and meltwater channels that terminate within 30 km of modern ice margins. Shells in glaciomarine deposits, collected beyond the LGM, indicate deglaciation by more extensive ice prior to 35 ka BP. More than 60 14C dates from glaciomarine sediments provide a chronology for past ice dynamics during the LGM. To the north, while many areas remained ice free due to severe aridity, several glaciers remained in contact with the sea until 7.1 ka BP. Farther south, most glaciers reached the coast and significantly infilled several fiords. This southward increase in glacier extent is due to larger glacial catchment basins and increased precipitation towards storm tracks in northern Baffin Bay. The earliest dates on deglaciation along the transect range from 8.1 to 7.7 ka BP. Initial retreat was controlled by the extent of the marine-based ice margins, which were destabilized by calving. Once landward of the sea, many glaciers stabilized until ~6.5 ka BP. Considerable interfiord variability in glacier dynamics is apparent. A paleoclimatic model is proposed linking past glacier activity in the Canadian High Arctic with the available ice core record. Greenland ice cores show that colder intervals, with depleted δ18O, were associated with reduced precipitation and storminess, which may have constrained ice buildup prior to ~15 ka BP. In contrast, the abrupt rise in δ18O after ~15 ka signals the onset of regional warming associated with increased storminess and precipitation (up to 200%). This may have occasioned a late buildup of High Arctic glaciers, which remained close to the last ice limit well into the Holocene.

scholarly journals Role of snow in the hydrology of a High Arctic riparian wetland

2008 ◽  
Vol 39 (4) ◽  
pp. 277-286 ◽  
Author(s):  
Kathy L. Young
Keyword(s):  
Weather Conditions ◽  
Growing Season ◽  
High Arctic ◽  
Ellesmere Island ◽  
Riparian Wetlands ◽  
Stream Channel ◽  
Riparian Wetland ◽  
Critical Links

Riparian wetlands are narrow strips of saturated and vegetated ground forming critical links between dry ground and waterways. The hydrology of a riparian wetland situated within a polar oasis landscape near Eastwind Lake, Ellesmere Island, Nunavut (80°80′N, 85°35′W) was investigated in 2006 using a combination of fieldwork and modelling. Supplemental information from 2005 was also employed. This study showed that deep snow in the nearby stream channel does not promote a period of extended over-bank flooding but instead initially serves as a dam blocking most streamwater from entering and flooding the wetland. It was not until the snow dam melts and disintegrates in response to favourable weather conditions that the wetland becomes flooded and fully recharged. This was a delay of three weeks from the previous year. For the remainder of the 2006 growing season, contributions of meltwater from late-lying snow beds located within and adjacent to the stream channel and near the headwaters were essential for maintaining saturated conditions in the wetland.

Tongues of Fire

2018 ◽  
Author(s):  
Nancy Farriss
Keyword(s):  
Cultural Difference ◽  
Language Contact ◽  
Social Contexts ◽  
Culture Contact ◽  
Rhetorical Strategies ◽  
Southern Mexico ◽  
Fine Grained ◽  
Indigenous Church ◽  
Cultural Gaps

Language and translation governed the creation of Mexican Christianity during the first centuries of colonial rule. Spanish missionaries collaborated with indigenous intellectuals to communicate the gospel in dozens of local languages that had previously lacked grammars, dictionaries, or alphabetic script. The major challenge to translators, more serious than the absence of written aids or the great diversity of languages and their phonetic and syntactical complexity, was the vast cultural difference between the two worlds. The lexical gaps that frustrated the search for equivalence in conveying fundamental Christian doctrines derived from cultural gaps that separated European experiences and concepts from those of the Indians. This study focuses on the Otomangue languages of Oaxaca in southern Mexico, especially Zapotec, and relates their role in the Dominican evangelizing program to the larger frame of culture contact in postconquest Mesoamerica. Fine-grained analysis of translated texts is used to reveal the rhetorical strategies of missionary discourse and combines with an examination of language contact in different social contexts. A major aim is to spotlight the role of the native elites in shaping what emerged as a new form of Christianity. As translators, chief catechists, and parish administrators they made evangelization in many respects an indigenous enterprise and the Mexican church it created an indigenous church.

How Artefacts Do Leadership: A Ventriloquial Analysis

2021 ◽  
pp. 089331892199807
Author(s):  
Jonathan Clifton ◽  
Fernando Fachin ◽  
François Cooren
Keyword(s):  
Organizational Communication ◽  
Recent Work ◽  
Distributed Leadership ◽  
Network Theory ◽  
Actor Network Theory ◽  
Fine Grained ◽  
Naturally Occurring ◽  
Human Actors

To date there has been little work that uses fine-grained interactional analyses of the in situ doing of leadership to make visible the role of non-human as well as human actants in this process. Using transcripts of naturally-occurring interaction as data, this study seeks to show how leadership is co-achieved by artefacts as an in-situ accomplishment. To do this we situate this study within recent work on distributed leadership and argue that it is not only distributed across human actors, but also across networks that include both human and non-human actors. Taking a discursive approach to leadership, we draw on Actor Network Theory and adopt a ventriloquial approach to sociomateriality as inspired by the Montreal School of organizational communication. Findings indicate that artefacts “do” leadership when a hybrid presence is made relevant to the interaction and when this presence provides authoritative grounds for influencing others to achieve the group’s goals.

scholarly journals Delta band activity contributes to the identification of command following in disorder of consciousness

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Gonzalo Rivera-Lillo ◽  
Emmanuel A. Stamatakis ◽  
Tristan A. Bekinschtein ◽  
David K. Menon ◽  
Srivas Chennu
Keyword(s):  
Functional Neuroimaging ◽  
Brain Activity ◽  
Disorder Of Consciousness ◽  
Fine Grained ◽  
Electrical Brain Activity ◽  
Delta Band ◽  
Delta Modulation ◽  
Command Following ◽  
Band Activity

AbstractThe overt or covert ability to follow commands in patients with disorders of consciousness is considered a sign of awareness and has recently been defined as cortically mediated behaviour. Despite its clinical relevance, the brain signatures of the perceptual processing supporting command following have been elusive. This multimodal study investigates the temporal spectral pattern of electrical brain activity to identify features that differentiated healthy controls from patients both able and unable to follow commands. We combined evidence from behavioural assessment, functional neuroimaging during mental imagery and high-density electroencephalography collected during auditory prediction, from 21 patients and 10 controls. We used a penalised regression model to identify command following using features from electroencephalography. We identified seven well-defined spatiotemporal signatures in the delta, theta and alpha bands that together contribute to identify DoC subjects with and without the ability to follow command, and further distinguished these groups of patients from controls. A fine-grained analysis of these seven signatures enabled us to determine that increased delta modulation at the frontal sensors was the main feature in command following patients. In contrast, higher frequency theta and alpha modulations differentiated controls from both groups of patients. Our findings highlight a key role of spatiotemporally specific delta modulation in supporting cortically mediated behaviour including the ability to follow command. However, patients able to follow commands nevertheless have marked differences in brain activity in comparison with healthy volunteers.

Job Resources and Strengths Use in Relation to Employee Performance: A Contextualized View

2021 ◽  
pp. 003329412199778
Author(s):  
Luca Tisu ◽  
Andrei Rusu ◽  
Coralia Sulea ◽  
Delia Vîrgă
Keyword(s):  
Employee Performance ◽  
Job Demands ◽  
Job Resources ◽  
Conservation Of Resources ◽  
Role Clarity ◽  
Fine Grained ◽  
Strengths Use ◽  
Individual Strategies ◽  
Moderator Role

Job resources play a prominent role in employee performance literature, yet a fine-grained understanding of how resources are relevant for several performance types is still needed. Relying on the Job Demands-Resources and Conservation of Resources theories, the present study addresses this call in two ways. First, it examines the predictive effect of four job resources (i.e., role clarity, feedback, autonomy, and opportunities for development) on nine types of performance (i.e., proficiency, adaptivity, and proactivity as an individual, team, and organization member). Second, it tests the moderator role of strengths use in these relationships. Data was gathered from a sample of Romanian employees (N = 332) and analyzed via hierarchical multiple linear regression. The results indicate that the selected job resources are, indeed, predictors of different types of employee performance and not in a unitary manner. Role clarity and feedback appear to be the most relevant predictors for various performance types, while autonomy seems to be the least important. Also, strengths use moderates these relationships, but in a reinforcing manner only regarding opportunities for development. The interaction of strengths use with role clarity and feedback renders the latter two obsolete, indicating that individual strategies may act as substitutes for job resources. These findings add to the Job Demands-Resources theory's versatile nature and provide more clarity to practitioners who plan interventions to enhance specific performance types, taking individual strategies into account.

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