scholarly journals GIS analyses of ice-sheet erosional impacts on the exposed shield of Baffin Island, eastern Canadian Arctic

2015 ◽  
Vol 52 (11) ◽  
pp. 966-979 ◽  
Author(s):  
Karin Ebert
Keyword(s):  
Ice Sheet ◽  
Canadian Arctic ◽  
Laurentide Ice Sheet ◽  
Baffin Island ◽  
Glacial Erosion ◽  
Ice Sheet Erosion ◽  
The Impact ◽  
Exposure Ages ◽  
Eastern Canadian Arctic ◽  
Sheet Erosion

The erosional impacts of former ice sheets on the low-relief bedrock surfaces of Northern Hemisphere shields are not well understood. This paper assesses the variable impacts of glacial erosion on a portion of Baffin Island, eastern Canadian Arctic, between 68° and 72°N and 66° and 80°W. This tilted shield block was covered repeatedly by the Laurentide Ice Sheet during the late Cenozoic. The impact of ice-sheet erosion is examined with GIS analyses using two geomorphic parameters: lake density and terrain ruggedness. The resulting patterns generally conform to published data from other remote sensing studies, geological observations, cosmogenic exposure ages, and the distribution of the chemical index of alteration for tills. Lake density and terrain ruggedness are thereby demonstrated to be useful quantitative indicators of variable ice-sheet erosional impacts across Baffin Island. Ice-sheet erosion was most effective in the lower western parts of the lowlands, in a west–east-oriented band at around 350–400 m a.s.l., and in fjord-onset zones in the uplifted eastern region. Above the 350–400 m a.s.l. band and between the fjord-onset zones, ice-sheet erosion was not sufficient to create extensive ice-roughened or streamlined bedrock surfaces. The exception — where lake density and terrain ruggedness indicate that ice-sheet erosion had a scouring effect all across the study area — was in an area from Foxe Basin to Home Bay with elevations <400 m a.s.l. These morphological contrasts link to former ice-sheet basal thermal regimes during the Pleistocene. The zone of low glacial erosion surrounding the cold-based Barnes Ice Cap probably represents the ice cap’s greater extent during successive Pleistocene cold stages. Inter-fjord plateaus with few ice-sheet bedforms remained cold-based throughout multiple Pleistocene glaciations. In contrast, zones of high lake density and high terrain ruggedness are a result of the repeated development of fast-flowing, erosive ice in warm-based zones beneath the Laurentide Ice Sheet. These zones are linked to greater ice thickness over western lowland Baffin Island. However, adjacent lowland surfaces with similar elevations of non-eroded, weakly eroded, and ice-scoured shield bedrock indicate that—even in areas of high lake density and terrain ruggedness—the total depth of ice sheet erosion did not exceed 50 m.

scholarly journals Ice-Sheet Erosion—A Result of Maximum Conditions?

1979 ◽  
Vol 23 (89) ◽  
pp. 402-404 ◽  
Author(s):  
D. E. Sugden
Keyword(s):  
Steady State ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Gradual Transition ◽  
Glacial Erosion ◽  
Mountain Glaciers ◽  
State Models ◽  
Ice Sheet Erosion ◽  
The Relationship ◽  
Sheet Erosion

Abstract Understanding the relationship between the morphology of former ice-sheet beds and glaciological processes is handicapped by the difficulty of establishing which stage of a cycle of ice-sheet growth and decay is responsible for most erosion. Discussions at this conference and in the literature display a variety of opinions, some favouring periods of ice-sheet build up, others periods of fluctuations, and still others steady-state maximum conditions. Here it is suggested that there is geomorphological evidence which points to the dominance of maximum conditions. Along the eastern margins of the Laurentide and Greenland ice sheets there is a sharp discontinuity between Alpine relief which stood above the ice-sheet surface at the maximum and plateau scenery which was covered by the ice sheet. Often the two types of relief are adjacent and yet separated by an altitudinal difference of only 100–200 m. The existence of an abrupt rather than gradual transition from one relief type to the other suggests that most glacial sculpture must have taken place while the ice sheet was at its maximum extent. In other geomorphological situations where high mountains were submerged by ice sheets, the major erosional landforms are frequently found to relate to ice sheets rather than to local mountain glaciers, again suggesting the dominance of erosion during full ice-sheet conditions. Finally, the identification of patterns of glacial erosion on an ice-sheet scale in North America and Greenland points to erosion when the ice sheets were fully expanded, rather than to the variable flow conditions associated with growth or decay. If ice-sheet erosion is accepted as being a result of maximum conditions, then it places certain constraints on glacial theory, for example the need to develop theories of glacial erosion which apply beneath ice thicknesses of several thousand metres. It also suggests that the use of steady-state models of ice sheets is likely to be a profitable way of relating glaciological processes to the morphology of former ice-sheet beds.

scholarly journals Ice-Sheet Erosion—A Result of Maximum Conditions?

1979 ◽  
Vol 23 (89) ◽  
pp. 402-404
Author(s):  
D. E. Sugden
Keyword(s):  
Steady State ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Gradual Transition ◽  
Glacial Erosion ◽  
Mountain Glaciers ◽  
State Models ◽  
Ice Sheet Erosion ◽  
The Relationship ◽  
Sheet Erosion

AbstractUnderstanding the relationship between the morphology of former ice-sheet beds and glaciological processes is handicapped by the difficulty of establishing which stage of a cycle of ice-sheet growth and decay is responsible for most erosion. Discussions at this conference and in the literature display a variety of opinions, some favouring periods of ice-sheet build up, others periods of fluctuations, and still others steady-state maximum conditions. Here it is suggested that there is geomorphological evidence which points to the dominance of maximum conditions.Along the eastern margins of the Laurentide and Greenland ice sheets there is a sharp discontinuity between Alpine relief which stood above the ice-sheet surface at the maximum and plateau scenery which was covered by the ice sheet. Often the two types of relief are adjacent and yet separated by an altitudinal difference of only 100–200 m. The existence of an abrupt rather than gradual transition from one relief type to the other suggests that most glacial sculpture must have taken place while the ice sheet was at its maximum extent. In other geomorphological situations where high mountains were submerged by ice sheets, the major erosional landforms are frequently found to relate to ice sheets rather than to local mountain glaciers, again suggesting the dominance of erosion during full ice-sheet conditions. Finally, the identification of patterns of glacial erosion on an ice-sheet scale in North America and Greenland points to erosion when the ice sheets were fully expanded, rather than to the variable flow conditions associated with growth or decay.If ice-sheet erosion is accepted as being a result of maximum conditions, then it places certain constraints on glacial theory, for example the need to develop theories of glacial erosion which apply beneath ice thicknesses of several thousand metres. It also suggests that the use of steady-state models of ice sheets is likely to be a profitable way of relating glaciological processes to the morphology of former ice-sheet beds.

Deglaciation of the Greenland and Laurentide ice sheets interrupted by glacier advance during abrupt coolings

2020 ◽  
Author(s):  
Nicolas Young ◽  
Jason Briner ◽  
Gifford Miller ◽  
Alia Lesnek ◽  
Sarah Crump ◽  
...  
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Holocene ◽  
Laurentide Ice Sheet ◽  
Baffin Island ◽  
Alpine Glacier ◽  
Baffin Bay ◽  
Warming World ◽  
Exposure Ages

&lt;p&gt;The early Holocene (11.7 ka to 8.2 ka) represents the most recent period when the Laurentide and Greenland ice sheets underwent large-scale recession. Moreover, this ice-sheet recession occurred under the backdrop of regional temperatures that were similar to or warmer than today, and comparable to those projected for the upcoming centuries. Reconstructing Laurentide and Greenland ice sheet behavior during the early Holocene, and elucidating the mechanisms dictating this behavior may serve as a partial analog for future Greenland ice-sheet change in a warming world. Here, we use 123 new &lt;sup&gt;10&lt;/sup&gt;Be surface exposure ages from two sites on Baffin Island and southwestern Greenland that constrain the behavior of the Laurentide and Greenland ice sheets, and an independent alpine glacier during the early Holocene. On Baffin Island, sixty-one &lt;sup&gt;10&lt;/sup&gt;Be ages reveal that advances and/or stillstands of the Laurentide Ice Sheet and an alpine glacier occurred in unison around 11.8 ka, 10.3 ka, and 9.2 ka. Sixty-two &lt;sup&gt;10&lt;/sup&gt;Be ages from southwestern Greenland indicate that the GrIS margin experienced re-advances or stillstands around 11.6 ka, 10.4 ka, 9.1 ka, 8.1 ka, and 7.3 ka. Our results reveal that alpine glaciers and the Laurentide and Greenland ice sheets responded in unison to abrupt early Holocene climate perturbations in the Baffin Bay region. We suggest that during the warming climate of the early Holocene, freshening of the North Atlantic Ocean induced by a melting Laurentide Ice Sheet resulted in regional abrupt cooling and brief periods of ice-sheet stabilization superimposed on net glacier recession. These observations point to a negative feedback mechanism inherent to melting ice sheets in the Baffin Bay region that slows ice-sheet recession during intervals of otherwise rapid deglaciation.&lt;/p&gt;

Conodont paleontology and biostratigraphy of Ordovician carbonates and petroliferous carbonates on Southampton, Baffin, and Akpatok islands in the eastern Canadian Arctic

1989 ◽  
Vol 26 (10) ◽  
pp. 1880-1903 ◽  
Author(s):  
Alexander D. McCracken ◽  
Godfrey S. Nowlan
Keyword(s):  
Canadian Arctic ◽  
Bedding Plane ◽  
Baffin Island ◽  
Jordan River ◽  
Oil Shales ◽  
Age Range ◽  
Eastern Canadian Arctic

Carbonate and petroliferous carbonate units ("oil shales") on Southampton, Baffin, and Akpatok islands have yielded a total of 2277 conodonts, the more biostratigraphically useful of which indicate not all units are correlative. The Boas River "shale", the lower of the two petroliferous units on Southampton Island, overlies the Bad Cache Rapids Group and contains a diverse fauna, including elements of Amorphognathus ordovicicus Branson and Mehl. Previous reports have indicated the presence of Culumbodina penna Sweet, a species whose range only barely overlaps that of A. ordovicicus in the middle Maysvillian. Carbonate beds and bedding-plane surfaces of the higher Red Head Rapids Formation at Sixteen Mile Brook yielded A. ordovicicus faunas containing Aphelognathus cf. A. divergens Sweet. These beds are likely Richmondian, since A. divergens is known elsewhere only from Richmondian strata. A metasicula of "Glyptograptus" hudsoni Jackson, several natural conodont assemblages, and fused enigmatic coniform elements were also found at Sixteen Mile Brook.The petroliferous unit in unnamed strata at Amadjuak Lake on Baffin Island contains Belodina area Sweet, which is indicative of a late Edenian to early Maysvillian age. Conodonts from the petroliferous strata at Jordan River on Baffin Island suggest a Trentonian to early Maysvillian age. The conodonts recovered from unnamed strata on Akpatok Island are not very diagnostic but indicate an age range from Shermanian to Gamachian.

Improved reconstruction of the southeastern Laurentide Ice Sheet deglaciation: constraining ice thinning using in-situ cosmogenic 10Be and 14C and critically evaluating different retreat rate chronometers

2020 ◽  
Author(s):  
Christopher Halsted ◽  
Jeremy Shakun ◽  
Lee Corbett ◽  
Paul Bierman ◽  
P. Thompson Davis ◽  
...  
Keyword(s):  
United States ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Ice Thickness ◽  
Northeastern United States ◽  
Terminal Moraine ◽  
Ice Volume ◽  
Ice Retreat ◽  
Exposure Ages

&lt;p&gt;In the northeastern United States, there are extensive geochronologic and geomorphic constraints on the deglaciation of the southeastern Laurentide Ice Sheet; thus, it is an ideal area for large-scale ice volume reconstructions and comparison between different ice retreat chronometers. Varve chronologies, lake and bog-bottom radiocarbon ages, and cosmogenic nuclide exposure ages constrain the timing of ice retreat, but the inferred ages exhibit considerable noise and sometimes disagree. Additionally, there are few empirical constraints on ice thinning, forcing ice volume reconstructions to rely on geophysically-based ice thickness models. Here, we aim to improve the understanding of the southeastern Laurentide Ice Sheet recession by (1) adding extensive ice thickness constraints and (2) compiling all available deglacial chronology data in the region to investigate discrepancies between different chronometers.&lt;/p&gt;&lt;p&gt;To provide insight about ice sheet thinning history, we collected 120 samples for in-situ &lt;sup&gt;10&lt;/sup&gt;Be and 10 samples for in-situ &lt;sup&gt;14&lt;/sup&gt;C cosmogenic exposure dating from various elevations at 13 mountains in the northeastern United States. By calculating ages of exposure at different elevations across this region, we reconstruct paleo-ice surface lowering of the southeastern Laurentide Ice Sheet during deglaciation. Where we suspect that &lt;sup&gt;10&lt;/sup&gt;Be remains from pre-Last Glacial Maximum periods of exposure, in-situ &lt;sup&gt;14&lt;/sup&gt;C is used to infer the erosional history and minimum exposure age of samples.&lt;/p&gt;&lt;p&gt;Presently, we have measured &lt;sup&gt;10&lt;/sup&gt;Be in 73 samples. Mountain-top exposure ages located within 150 km of the southeastern Laurentide Ice Sheet terminal moraine indicate that near-margin thinning began early in the deglacial period (~19.5 to 17.5 ka), coincident with the slow initial margin retreat indicated by varve records. Exposure ages from several mountains further inland (&gt;400 km north of terminal moraine) collected over ~1000 m of elevation range record rapid ice thinning between 14.5 and 13 ka. Ages within each of these vertical transects are similar within 1&amp;#963; internal uncertainty, indicating that ice thinned quickly, less than a few hundred years at most. This rapid thinning occurred at about the same time that varve records indicate accelerated ice margin retreat (14.6&amp;#8211;12.9 ka), providing evidence of substantial ice volume loss during the B&amp;#248;lling-Aller&amp;#248;d warm period.&lt;/p&gt;&lt;p&gt;Our critical evaluation of deglacial chronometers, including valley-bottom &lt;sup&gt;10&lt;/sup&gt;Be ages from this project, is intended to constrain ice margin retreat rates and timing in the region. Ultimately, we will integrate our ice thickness over time constraints with the existing network of deglacial ages to create a probabilistic reconstructions of the southeastern Laurentide Ice Sheet volume during its recession through the northeastern United States.&lt;/p&gt;

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