Reconstructing the Cordilleran Ice Sheet in northern British Columbia during the Late Pleistocene climate reversals

2020 ◽  
Author(s):  
Helen Dulfer ◽  
Martin Margold
Keyword(s):  
British Columbia ◽  
Late Pleistocene ◽  
Regional Scale ◽  
Ice Sheet ◽  
Younger Dryas ◽  
Western Canada ◽  
Alpine Glaciers ◽  
Pleistocene Climate ◽  
Cordilleran Ice Sheet ◽  
Exposure Ages

<p>The Cordilleran Ice Sheet (CIS) repeatedly covered western Canada during the Pleistocene and attained a volume and area similar to that of the present-day Greenland Ice Sheet. Deglaciation of the CIS following the Last Glacial Maximum (LGM) directly affected atmosphere and ocean circulation, eustatic sea level, and human migration from Asia to North America. It has recently been shown that the rapid climate oscillations at the end of the Pleistocene had a dramatic effect on the CIS. Data on glacial isostatic adjustment and cosmogenic nuclide exposure ages indicate that abrupt warming at the onset of the Bølling-Allerød caused significant thinning of the ice sheet, resulting in a fifty percent reduction in mass, while the Younger Dryas cooling caused the expansion of alpine glaciers across the mountains of western Canada. However, the mountainous subglacial terrain makes it challenging to reconstruct the regional-scale deglaciation dynamics of the ice sheet, and its configuration during this period of rapid change remains poorly constrained. </p><p>Here we use the glacial landform record to reconstruct the ice sheet configuration for the central sector of the CIS, over the Cassiar and Omineca Mountains in northern British Columbia, during the Late Pleistocene climate reversals. We present the first regional-scale reconstruction of the CIS following the Bølling-Allerød warming, whereby the ice sheet was reduced to a labyrinth of valley glaciers fed by ice dispersal centres located over the Skeena Mountains in the south and Coast Mountains in the west. Additionally, numerous lateral and terminal late glacial moraines delineate the extent of alpine glaciers, ice caps and ice fields that regrew on mountain peaks above the CIS during the Younger Dryas. Cross-cutting relationships indicate that the valley glaciers of the CIS were slower to respond to the Younger Dryas cooling than the mountain glaciers.</p>

Pre-Younger Dryas resurgence of the southwestern margin of the Cordilleran ice sheet, British Columbia, Canada

Boreas ◽  
2008 ◽  
Vol 26 (3) ◽  
pp. 261-278 ◽  
Author(s):  
JOHN J. CLAGUE ◽  
R. W. MATHEWES ◽  
J.-P. GUILBAULT ◽  
I. HUTCHINSON ◽  
B. D. RICKETTS
Keyword(s):  
British Columbia ◽  
Ice Sheet ◽  
Younger Dryas ◽  
Southwestern Margin ◽  
Cordilleran Ice Sheet

scholarly journals Deglaciation of the Cordillera of Western Canada at the end of the Pleistocene

2017 ◽  
Vol 43 (2) ◽  
pp. 449 ◽  
Author(s):  
J.J. Clague
Keyword(s):  
British Columbia ◽  
Ice Sheet ◽  
Ice Cover ◽  
High Elevation ◽  
Coast Mountains ◽  
Western Margin ◽  
Warming Climate ◽  
Glacier Ice ◽  
Cordilleran Ice Sheet ◽  
Exposure Ages

Nearly all of what is now British Columbia and adjacent areas were covered by an ice sheet at the maximum of the Last Glaciation (MIS 2) about 18,000 years ago. By 11,000 years ago, the Cordilleran Ice Sheet had disappeared, a victim of warming climate, eustatic sea-level rise along its western margin, and perhaps a reduction in precipitation. Deglaciation proceeded by frontal retreat at the periphery of the ice sheet and by downwasting, complex frontal retreat, and localized stagnation in its interior areas. The chronology of deglaciation is constrained, albeit with inherent dating errors, by AMS radiocarbon and 10Be surface exposure ages. High-elevation sites at the western margin of the British Columbia Interior Plateau, east of the Coast Mountains, became ice-free between about 15,000 and 12,000 years ago. Ice cover in the southern Coast Mountains was sufficiently extensive during the Younger Dryas Chronozone (12,900-11,700 years ago) that glaciers advanced into low-lying areas north and east of Vancouver. At the same time, however, a labyrinth of dead or dying tongues of glacier ice covered some interior valleys. By 11,000 years ago, ice cover in the Canadian Cordillera was no more extensive than it is today.

Vashon Drift: definition of the formation in the Georgia Depression, southwest British Columbia

1985 ◽  
Vol 22 (5) ◽  
pp. 748-757 ◽  
Author(s):  
Stephen R. Hicock ◽  
John E. Armstrong
Keyword(s):  
British Columbia ◽  
Ice Sheet ◽  
Southwestern Part ◽  
Maximum Expansion ◽  
Source Areas ◽  
Alpine Glaciers ◽  
Time Space ◽  
Late Wisconsinan ◽  
Cordilleran Ice Sheet ◽  
Definition Of

Vashon Drift was deposited during the Fraser Glaciation (late Wisconsinan) at the time of maximum expansion of the southwestern part of the Cordilleran ice sheet when it filled the Georgia Depression about 14 500 years ago. The drift is present throughout the depression and comprises till and glaciofluvial and glaciolacustrine sediments derived from source areas surrounding the coastal trough. It is overlain by Capilano Sediments and underlain by Quadra Sand, also of Fraser age. Drift deposition was diachronous and complex, probably caused by alpine glaciers coalescing in the trough with the ice margin repeatedly grounding and floating in seawater. Studies of bedrock striae, till fabrics, and clast provenance reveal that Vashon ice movement was generally southward, although locally controlled by topography. A time–space diagram is presented that confirms the long-held hypothesis that advance and decay of Vashon ice were rapid.

Advance of alpine glaciers during final retreat of the Cordilleran ice sheet in the Finlay River area, northern British Columbia, Canada

2008 ◽  
Vol 69 (2) ◽  
pp. 188-200 ◽  
Author(s):  
Thomas R. Lakeman ◽  
John J. Clague ◽  
Brian Menounos
Keyword(s):  
British Columbia ◽  
Little Ice Age ◽  
Sediment Cores ◽  
Ice Sheet ◽  
Late Glacial ◽  
Plant Macrofossils ◽  
Ice Age ◽  
Last Glaciation ◽  
Alpine Glaciers ◽  
Cordilleran Ice Sheet

Sharp-crested moraines, up to 120 m high and 9 km beyond Little Ice Age glacier limits, record a late Pleistocene advance of alpine glaciers in the Finlay River area in northern British Columbia. The moraines are regional in extent and record climatic deterioration near the end of the last glaciation. Several lateral moraines are crosscut by meltwater channels that record downwasting of trunk valley ice of the northern Cordilleran ice sheet. Other lateral moraines merge with ice-stagnation deposits in trunk valleys. These relationships confirm the interaction of advancing alpine glaciers with the regionally decaying Cordilleran ice sheet and verify a late-glacial age for the moraines. Sediment cores were collected from eight lakes dammed by the moraines. Two tephras occur in basal sediments of five lakes, demonstrating that the moraines are the same age. Plant macrofossils from sediment cores provide a minimum limiting age of 10,550–10,250 cal yr BP (9230±5014C yr BP) for abandonment of the moraines. The advance that left the moraines may date to the Younger Dryas period. The Finlay moraines demonstrate that the timing and style of regional deglaciation was important in determining the magnitude of late-glacial glacier advances.

Deglaciation of the central sector of the Cordilleran Ice Sheet in northern British Columbia

2021 ◽  
Author(s):  
Helen Dulfer ◽  
Martin Margold
Keyword(s):  
British Columbia ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Late Glacial ◽  
Glacial Period ◽  
Last Glacial ◽  
Late Glacial Period ◽  
Alpine Glaciers ◽  
Cordilleran Ice Sheet ◽  
The Last Glacial

<p>The Cordilleran Ice Sheet (CIS) repeatedly covered western Canada during the Pleistocene and attained a volume and area similar to that of the present-day Greenland Ice Sheet at the Last Glacial Maximum. Numerical modelling studies of the CIS during the last glacial-interglacial cycle indicate the central sector of this ice sheet, located in mountainous northern British Columbia, played an important role during both the advance and retreat phases. Additionally, the models indicate that the rapid climate oscillations at the end of the Pleistocene had a dramatic effect on the CIS. The abrupt warming at the onset of the Bølling-Allerød caused significant thinning of the ice sheet, resulting in a fifty percent reduction in mass, while the subsequent cooling caused the expansion of alpine glaciers across the former central sector of the CIS. However, the mountainous terrain and remote location have thus far impeded our understanding of this important region of the CIS, and the ice sheet configuration during the Late Glacial remains poorly constrained. </p><p>Here we use the glacial landform record to reconstruct the deglaciation dynamics of the central sector of the CIS during the Late Pleistocene climate reversals. Numerous high elevation meltwater channels suggests the early emergence of mountain peaks above the ice sheet and the configuration of ice marginal landforms, particularly lateral meltwater channels, eskers, kame terraces and ice-contact deltas, allows the westward retreat of the ice margin to be traced towards ice dispersal centres in the Skeena and Coast mountains. Hundreds of arcuate, sharp-crested terminal moraines delineate the extent of alpine glaciers, ice caps and ice fields that regrew on mountain peaks above the CIS and numerical dating indicates that this readvance occurred during the Late Glacial period. Additionally, at some locations, cross-cutting relationships preserve the interaction of the local readvance glaciers with the trunk glaciers of the CIS, allowing the extent of the central sector of the CIS during the Late Glacial period to be reconstructed for the first time.  </p>

New constraints on the last deglaciation of the Cordilleran Ice Sheet in coastal Southeast Alaska

2020 ◽  
Vol 96 ◽  
pp. 140-160 ◽  
Author(s):  
Alia J. Lesnek ◽  
Jason P. Briner ◽  
James F. Baichtal ◽  
Alex S. Lyles
Keyword(s):  
Ice Sheet ◽  
Last Deglaciation ◽  
Rapid Phase ◽  
Southeast Alaska ◽  
Alpine Glaciers ◽  
Air Temperatures ◽  
The Last Deglaciation ◽  
Cordilleran Ice Sheet ◽  
Exposure Ages ◽  
Outer Coast

AbstractUnderstanding marine-terminating ice sheet response to past climate transitions provides valuable long-term context for observations of modern ice sheet change. Here, we reconstruct the last deglaciation of marine-terminating Cordilleran Ice Sheet (CIS) margins in Southeast Alaska and explore potential forcings of western CIS retreat. We combine 27 new cosmogenic 10Be exposure ages, 13 recently published 10Be ages, and 25 new 14C ages from raised marine sediments to constrain CIS recession. Retreat from the outer coast was underway by 17 ka, and the inner fjords and sounds were ice-free by 15 ka. After 15 ka, the western margin of the CIS became primarily land-terminating and alpine glaciers disappeared from the outer coast. Isolated alpine glaciers may have persisted in high inland peaks until the early Holocene. Our results suggest that the most rapid phase of CIS retreat along the Pacific coast occurred between ~17 and 15 ka. This retreat was likely driven by processes operating at the ice-ocean interface, including sea level rise and ocean warming. CIS recession after ~15 ka occurred during a time of climatic amelioration in this region, when both ocean and air temperatures increased. These data highlight the sensitivity of marine-terminating CIS regions to deglacial climate change.

Sign in / Sign up

Export Citation Format

Share Document