scholarly journals Regional subglacial quarrying and abrasion below hard‐bedded palaeo‐ice streams crossing the Shield–Palaeozoic boundary of central Canada: the importance of substrate control

Boreas ◽  
2021 ◽  
Author(s):  
Syed Bukhari ◽  
Nick Eyles ◽  
Shane Sookhan ◽  
Riley Mulligan ◽  
Roger Paulen ◽  
...  
Keyword(s):  
Ice Streams ◽  
Central Canada

scholarly journals Laurentide Ice Sheet basal temperatures during the last glacial cycle as inferred from borehole data

2016 ◽  
Vol 12 (1) ◽  
pp. 115-127 ◽  
Author(s):  
C. Pickler ◽  
H. Beltrami ◽  
J.-C. Mareschal
Keyword(s):  
Ice Sheet ◽  
Internal Heat ◽  
Ground Surface ◽  
Laurentide Ice Sheet ◽  
Glacial Cycle ◽  
Ice Streams ◽  
Borehole Data ◽  
Last Glacial ◽  
Central Canada ◽  
The Last Glacial

Abstract. Thirteen temperature–depth profiles ( ≥  1500 m) measured in boreholes in eastern and central Canada were inverted to determine the ground surface temperature histories during and after the last glacial cycle. The sites are located in the southern part of the region that was covered by the Laurentide Ice Sheet. The inversions yield ground surface temperatures ranging from −1.4 to 3.0 °C throughout the last glacial cycle. These temperatures, near the pressure melting point of ice, allowed basal flow and fast flowing ice streams at the base of the Laurentide Ice Sheet. Despite such conditions, which have been inferred from geomorphological data, the ice sheet persisted throughout the last glacial cycle. Our results suggest some regional trends in basal temperatures with possible control by internal heat flow.

scholarly journals Laurentide Ice Sheet basal temperatures at the Last Glacial Cycle as inferred from borehole data

2015 ◽  
Vol 11 (4) ◽  
pp. 3937-3971
Author(s):  
C. Pickler ◽  
H. Beltrami ◽  
J.-C. Mareschal
Keyword(s):  
Ice Sheet ◽  
Internal Heat ◽  
Ground Surface ◽  
Laurentide Ice Sheet ◽  
Glacial Cycle ◽  
Ice Streams ◽  
Borehole Data ◽  
Last Glacial ◽  
Central Canada ◽  
The Last Glacial

Abstract. Thirteen temperature-depth profiles (≥ 1500 m) measured in boreholes in eastern and central Canada were inverted to determine the ground surface temperature histories during and after the last glacial cycle. The sites are located in the southern part of the region covered by the Laurentide Ice Sheet. The inversions yield ground surface temperatures ranging from −1.4 to 3.0 °C throughout the last glacial cycle. These temperatures, near the pressure melting point of ice, allowed basal flow and fast flowing ice streams at the base of the Laurentide Ice Sheet. Despite such conditions, which have been inferred from geomorphological data, the ice sheet persisted throughout the last glacial cycle. Our results suggest some regional trends in basal temperatures with possible control by internal heat flow.

Interannual Variability of North American Winter Temperature Extremes and Its Associated Circulation Anomalies in Observations and CMIP5 Simulations

2020 ◽  
Vol 33 (3) ◽  
pp. 847-865 ◽  
Author(s):  
B. Yu ◽  
H. Lin ◽  
V. V. Kharin ◽  
X. L. Wang
Keyword(s):  
North America ◽  
Surface Temperature ◽  
Atmospheric Circulation ◽  
North American ◽  
North Pacific ◽  
Large Scale ◽  
Temperature Extremes ◽  
Temperature Extreme ◽  
Central Canada ◽  
Leading Mode

AbstractThe interannual variability of wintertime North American surface temperature extremes and its generation and maintenance are analyzed in this study. The leading mode of the temperature extreme anomalies, revealed by empirical orthogonal function (EOF) analyses of December–February mean temperature extreme indices over North America, is characterized by an anomalous center of action over western-central Canada. In association with the leading mode of temperature extreme variability, the large-scale atmospheric circulation features an anomalous Pacific–North American (PNA)-like pattern from the preceding fall to winter, which has important implications for seasonal prediction of North American temperature extremes. A positive PNA pattern leads to more warm and fewer cold extremes over western-central Canada. The anomalous circulation over the PNA sector drives thermal advection that contributes to temperature anomalies over North America, as well as a Pacific decadal oscillation (PDO)-like sea surface temperature (SST) anomaly pattern in the midlatitude North Pacific. The PNA-like circulation anomaly tends to be supported by SST warming in the tropical central-eastern Pacific and a positive synoptic-scale eddy vorticity forcing feedback on the large-scale circulation over the PNA sector. The leading extreme mode–associated atmospheric circulation patterns obtained from the observational and reanalysis data, together with the anomalous SST and synoptic eddy activities, are reasonably well simulated in most CMIP5 models and in the multimodel mean. For most models considered, the simulated patterns of atmospheric circulation, SST, and synoptic eddy activities have lower spatial variances than the corresponding observational and reanalysis patterns over the PNA sector, especially over the North Pacific.

Drought signals inferred from ring-width and stable carbon isotope chronologies from Thuja occidentalis trees growing at their northwestern distribution limit, central Canada

2012 ◽  
Vol 42 (3) ◽  
pp. 517-531 ◽  
Author(s):  
Robert Au ◽  
Jacques C. Tardif
Keyword(s):  
Tree Ring ◽  
Tree Rings ◽  
Stable Carbon Isotopes ◽  
Stable Carbon Isotope ◽  
Ring Width ◽  
Ring Formation ◽  
Moisture Regime ◽  
Stable Carbon ◽  
Thuja Occidentalis ◽  
Central Canada

Stable carbon isotopes (δ13C) fixed in tree rings are dependent upon environmental conditions. Old northern white-cedar ( Thuja occidentalis L.) trees were sampled at their northwestern limit of distribution in central Canada. The objectives of the study were (i) to investigate the association between tree-ring δ13C values and radial growth in addition to the response of these variables to climate, (ii) to assess site differences between two sites varying in moisture regime, and (iii) to compare tree-ring δ13C of T. occidentalis with that of other boreal tree species growing at the northern limit of their distribution in central Canada. Over 2500 tree rings comprised of 15 T. occidentalis trees were analyzed for δ13C. Annually resolved δ13C (1650–2006) and ring-width (1542–2006) chronologies were developed. During the year of ring formation, ring width was associated with spring and early-summer conditions, whereas δ13C was more indicative of overall summer conditions. However, compared with δ13C values, ring width was more often associated with climate conditions in the year prior to ring formation. Conditions conducive to moisture stress were important for both parameters. Although ring width and δ13C corresponded to the drought intervals of the 1790s, 1840s, 1890s, 1930s, and 1960–1970, ring width may be more responsive to prolonged drought than δ13C. Tree-ring δ13C could, however, provide important information regarding physiological adaptations to drought.

First records of Chrysodeixis chalcites (Lepidoptera: Noctuidae: Plusiinae) for east-central Canada

2013 ◽  
Vol 145 (3) ◽  
pp. 338-342 ◽  
Author(s):  
Henry Murillo ◽  
David W.A. Hunt ◽  
Sherah L. VanLaerhoven
Keyword(s):  
Insect Pest ◽  
Green Bean ◽  
Nonnative Species ◽  
East Central ◽  
Central Canada ◽  
Chrysodeixis Chalcites ◽  
Lepidoptera Noctuidae

AbstractSpecimens of Chrysodeixis chalcites (Esper) (Lepidoptera: Noctuidae) have been found in different municipalities in southwestern Ontario, Canada since 2008. This nonnative species occurs in tomato and green bean crops where it has the potential of becoming an important insect pest.

scholarly journals Drivers of abrupt Holocene shifts in West Antarctic ice stream direction determined from combined ice sheet modelling and geologic signatures

2014 ◽  
Vol 26 (6) ◽  
pp. 674-686 ◽  
Author(s):  
C.J. Fogwill ◽  
C.S.M. Turney ◽  
N.R. Golledge ◽  
D.H. Rood ◽  
K. Hippe ◽  
...  
Keyword(s):  
Flow Direction ◽  
Ice Sheet ◽  
Weddell Sea ◽  
Last Deglaciation ◽  
Ice Streams ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Ice Stream ◽  
Ice Sheet Modelling

AbstractDetermining the millennial-scale behaviour of marine-based sectors of the West Antarctic Ice Sheet (WAIS) is critical to improve predictions of the future contribution of Antarctica to sea level rise. Here high-resolution ice sheet modelling was combined with new terrestrial geological constraints (in situ14C and 10Be analysis) to reconstruct the evolution of two major ice streams entering the Weddell Sea over 20 000 years. The results demonstrate how marked differences in ice flux at the marine margin of the expanded Antarctic ice sheet led to a major reorganization of ice streams in the Weddell Sea during the last deglaciation, resulting in the eastward migration of the Institute Ice Stream, triggering a significant regional change in ice sheet mass balance during the early to mid Holocene. The findings highlight how spatial variability in ice flow can cause marked changes in the pattern, flux and flow direction of ice streams on millennial timescales in this marine ice sheet setting. Given that this sector of the WAIS is assumed to be sensitive to ocean-forced instability and may be influenced by predicted twenty-first century ocean warming, our ability to model and predict abrupt and extensive ice stream diversions is key to a realistic assessment of future ice sheet sensitivity.

Structural development of the Snow Lake Allochthon and its role in the evolution of the southeastern Trans-Hudson Orogen in Manitoba, central Canada

1999 ◽  
Vol 36 (11) ◽  
pp. 1881-1899 ◽  
Author(s):  
Jürgen Kraus ◽  
Paul F Williams
Keyword(s):  
Structural Development ◽  
Southeastern Part ◽  
External Zone ◽  
Local Boundary ◽  
Tectonic Model ◽  
Adjacent Part ◽  
Central Canada ◽  
Tectonic Transport ◽  
The One ◽  
Superior Craton

The Snow Lake Allochthon is a zone of tectonic interleaving of sedimentary rocks of an inverted marginal basin (Kisseynew Domain) with island-arc and oceanic rocks. It is located in the southeastern part of the exposed internal zone of the Paleoproterozoic Trans-Hudson Orogen in Manitoba, Canada, near the external zone (Superior collision zone or Thompson Belt), which constitutes the local boundary between the Trans-Hudson Orogen and the Archean Superior Craton. The Snow Lake Allochthon formed, was deformed, and was metamorphosed up to high grade at low to medium pressure during the Hudsonian orogeny as a result of the collision of Archean cratons ~1.84-1.77 Ga. Four generations of folds (F1-F4) that formed in at least three successive kinematic frames over a period of more than 30 Ma are described. Isoclinal to transposed southerly verging F1-2 structures are refolded by large, open to tight F3 folds and, locally, by open to tight F4 folds. The axes of the F1-2 folds are parallel or near parallel to the axes of F3 folds, owing to progressive reorientation of the F1-2 axes during south- to southwest-directed tectonic transport, followed by F3 refolding around the previous linear anisotropy. A tectonic model is presented that reconciles the distinct tectono-metamorphic developments in the Snow Lake Allochthon and the adjacent part of the Kisseynew Domain on the one hand, and in the Thompson Belt on the other, during final collision of the Trans-Hudson Orogen with the Superior Craton.

scholarly journals Hydrological Impacts of Warmer and Wetter Climate in Troutlake and Sturgeon River Basins in Central Canada

2014 ◽  
Vol 28 (15) ◽  
pp. 5319-5333 ◽  
Author(s):  
Woonsup Choi ◽  
Sung Joon Kim ◽  
Mark Lee ◽  
Kristina Koenig ◽  
Peter Rasmussen
Keyword(s):  
River Basins ◽  
Hydrological Impacts ◽  
Central Canada
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