Multiphase flow of the late Wisconsinan Cordilleran ice sheet in western Canada

Stumpf, Andrew J.; Broster, Bruce E.; Levson, Victor M.

doi:10.1130/0016-7606(2000)112<1850:mfotlw>2.0.co;2

Cited by 58 publications

(76 citation statements)

References 40 publications

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“…We consider it likely that this pattern characterized both stages and have therefore included it as a constraint for stage 5b. Regarding the Cordilleran Ice Sheet, Kleman et al (2010) concluded that there was flow-trace evidence for "old" configurations with more easterly dispersal centers (Stumpf et al, 2000) than the ones that prevailed in near-LGM time, but constraints on age and outline are lacking. Hence, the Cordilleran Ice Sheet is one element of the missing ice sheet problem, and it appears very likely that this region was at least partly glaciated during MIS 5d, 5b, and 4, but there is simply not enough geological and geomorphological data to suggest an outline.…”

Section: North Americamentioning

confidence: 99%

Pre-LGM Northern Hemisphere ice sheet topography

et al. 2013

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Abstract. We here reconstruct the paleotopography of Northern Hemisphere ice sheets during the glacial maxima of marine isotope stages (MIS) 5b and 4.We employ a combined approach, blending geologically based reconstruction and numerical modeling, to arrive at probable ice sheet extents and topographies for each of these two time slices. For a physically based 3-D calculation based on geologically derived 2-D constraints, we use the University of Maine Ice Sheet Model (UMISM) to calculate ice sheet thickness and topography. The approach and ice sheet modeling strategy is designed to provide robust data sets of sufficient resolution for atmospheric circulation experiments for these previously elusive time periods. Two tunable parameters, a temperature scaling function applied to a spliced Vostok-GRIP record, and spatial adjustment of the climatic pole position, were employed iteratively to achieve a good fit to geological constraints where such were available. The model credibly reproduces the first-order pattern of size and location of geologically indicated ice sheets during marine isotope stages (MIS) 5b (86.2 kyr model age) and 4 (64 kyr model age). From the interglacial state of two north-south obstacles to atmospheric circulation (Rocky Mountains and Greenland), by MIS 5b the emergence of combined Quebec-central Arctic and Scandinavian-Barents-Kara ice sheets had increased the number of such highland obstacles to four. The number of major ice sheets remained constant through MIS 4, but the merging of the Cordilleran and the proto-Laurentide Ice Sheet produced a single continent-wide North American ice sheet at the LGM.

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Section: North Americamentioning

confidence: 99%

Pre-LGM Northern Hemisphere ice sheet topography

et al. 2013

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“…The impressive life cycle of sockeye salmon has been repeated in this watershed since the retreat of the last glaciers 9-13 ka ago (Ricker 1940, Stumpf et al 2000. However, the trend over the last two decades has been a precipitous decline in numbers of returning adult Fraser River sockeye salmon from several large populations and general declines in productivity to levels below replacement.…”

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confidence: 99%

Tracking wild sockeye salmon smolts to the ocean reveals distinct regions of nocturnal movement and high mortality

et al. 2016

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Abstract. Few estimates of migration rates or descriptions of behavior or survival exist for wild populations of out-migrating Pacific salmon smolts from natal freshwater rearing areas to the ocean. Using acoustic transmitters and fixed receiver arrays across four years (2010-2013), we tracked the migration of >1850 wild sockeye salmon (Oncorhynchus nerka) smolts from Chilko Lake, British Columbia, to the coastal Pacific Ocean (>1000 km distance). Cumulative survival to the ocean ranged 3-10% among years, although this may be slightly underestimated due to technical limitations at the final receiver array. Distinct spatial patterns in both behavior and survival were observed through all years. In small, clear, upper-river reaches, downstream migration largely occurred at night at speeds up to 50 km/d and coincided with poor survival. Among years, only 57-78% of smolts survived the first 80 km. Parallel laboratory experiments revealed excellent short-term survival and unhindered swimming performance of dummy-tagged smolts, suggesting that predators rather than tagging effects were responsible for the initial high mortality of acoustic-tagged smolts. Migration speeds increased in the Fraser River mainstem (~220 km/d in some years), diel movement patterns ceased, and smolt survival generally exceeded 90% in this segment. Marine movement rates and survival were variable across years, with among-year segment-specific survival being the most variable and lowest (19-61%) during the final (and longest, 240 km) marine migration segment. Osmoregulatory preparedness was not expected to influence marine survival, as smolts could maintain normal levels of plasma chloride when experimentally exposed to saltwater (30 ppt) immediately upon commencing their migration from Chilko Lake. Transportation of smolts downstream generally increased survival to the farthest marine array. The act of tagging may have affected smolts in the marine environment in some years as dummy-tagged fish had poorer survival than control fish when transitioned to saltwater in laboratory-based experiments. Current fisheries models for forecasting the number of adult sockeye returning to spawn have been inaccurate in recent years and generally do not incorporate juvenile or smolt survival information. Our results highlight significant potential for early migration conditions to influence adult recruitment.

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“…Stea and Finck 2001) and palimpsest dispersal trains modifi ed by the later event (Parent et al 1996). It may be that till was not deposited and re-eroded by the subsequent movements, but that the drift was retained in the ice mass while ice fl ow was redirected, possibly due to a change in the location of ice-growth or ice drawdown (Stumpf et al 2000). However, the overall result is general eastward and northward dispersal patterns, albeit of different magnitudes for different areas.…”

Section: Discussionmentioning

confidence: 52%

Comparison of clast and matrix dispersal in till: Charlo-Atholville area, north-central New Brunswick

Dickson

Broster

Parkhill³

2004

atgeol

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Striations and dispersal patterns for till clasts and matrix geochemistry are used to defi ne fl ow directions of glacial transport across an area of about 800km 2 in the Charlo-Atholville area of north-central New Brunswick. A total of 170 clast samples and 328 till matrix samples collected for geochemical analysis across the region, were analyzed for a total of 39 elements. Major lithologic contacts used here to delineate till clast provenance were based on recent bedrock mapping. Eleven known mineral occurrences and a gossan are used to defi ne point source targets for matrix geochemical dispersal trains and to estimate probable distance and direction of transport from unknown sources. Clast trains are traceable for distances of approximately 10 km, whereas till geochemical dispersal patterns are commonly lost within 5 km of transport. Most dispersal patterns refl ect more than a single direction of glacial transport.These data indicate that a single till sheet, 1-4 m thick, was deposited as the dominant ice-fl ow direction fl uctuated between southeastward, eastward, and northward over the study area. Directions of early fl ow represent changes in ice sheet dominance, fi rst from the northwest and then from the west. Locally, eastward and northward fl ow represent the maximum erosive phases. The last directions of fl ow are likely due to late glacial ice sheet drawdown towards the valley outlet at Baie des Chaleurs. RÉSUMÉL'équipe utilise les striures et les tracés de dispersion des clastes de till ainsi que les caractéristiques géochimiques de la gangue pour défi nir les orientations d'écoulement du transport glaciaire dans un secteur d'environ 800 kilomètres carrés de la région de Charlo-Atholville, dans le centre-nord du Nouveau-Brunswick. On a prélevé dans la région au total 170 échantillons de clastes et 328 échantillons de gangue du till en vue d'analyses géochimiques, et on a analysé leur teneur en 39 éléments particuliers. Les principales zones de contact lithologique utilisées dans le cadre de cet exercice pour délimiter la provenance des clastes de till ont été basées sur de récents travaux de cartographie du substrat rocheux. Onze venues minérales reconnues et un chapeau ferrugineux servent à défi nir les objectifs des sources ponctuelles des tracés de dispersion géochimique de la gangue de même qu'à estimer l'orientation et la distance probables du transport à partir des sources inconnues. Il est possible de retracer les traînées de clastes sur des distances d'une dizaine de kilomètres, tandis que les tracés de dispersion géochimique du till s'effacent généralement avant moins de cinq kilomètres. La majorité des tracés de dispersion évoquent plus d'une direction de transport glaciaire.Ces données révèlent qu'une nappe de till particulière d'une épaisseur d'un à quatre mètres s'est déposée pendant que l'orientation prédominante des écoulements de glaces a varié entre le sud-est, l'est et le nord à l'intérieur du secteur d'étude. Les orientations de l'écoulement primitif représentent les ch...

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Multiphase flow of the late Wisconsinan Cordilleran ice sheet in western Canada

Cited by 58 publications

References 40 publications

Pre-LGM Northern Hemisphere ice sheet topography

Pre-LGM Northern Hemisphere ice sheet topography

Tracking wild sockeye salmon smolts to the ocean reveals distinct regions of nocturnal movement and high mortality

Comparison of clast and matrix dispersal in till: Charlo-Atholville area, north-central New Brunswick

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