Retreat pattern of the Cordilleran Ice Sheet in central British Columbia at the end of the last glaciation reconstructed from glacial meltwater landforms

Abstract

2013 (October): Retreat pattern of the Cordilleran Ice Sheet in central British Columbia at the end of the last glaciation reconstructed from glacial meltwater landforms.The Cordilleran Ice Sheet (CIS) covered much of the mountainous northwestern part of North America at least several times during the Pleistocene. The pattern and timing of its growth and decay are, however, poorly understood. Here, we present a reconstruction of the pattern of ice-sheet retreat in central British Columbia at the end of the last glaciation based on a palaeoglaciological interpretation of ice-marginal meltwater channels, eskers and deltas mapped from satellite imagery and digital elevation models. A consistent spatial pattern of highelevation (1600-2400 m a.s.l.), ice-marginal meltwater channels is evident across central British Columbia. These landforms indicate the presence of ice domes over the Skeena Mountains and the central Coast Mountains early during deglaciation. Ice sourced in the Coast Mountains remained dominant over the southern and east-central parts of the Interior Plateau during deglaciation. Our reconstruction shows a successive westward retreat of the ice margin from the western foot of the Rocky Mountains, accompanied by the formation and rapid evolution of a glacial lake in the upper Fraser River basin. The final stage of deglaciation is characterized by the frontal retreat of ice lobes through the valleys of the Skeena and Omineca Mountains and by the formation of large esker systems in the most prominent topographic lows of the Interior Plateau. We conclude that the CIS underwent a large-scale reconfiguration early during deglaciation and was subsequently diminished by thinning and complex frontal retreat towards the Coast Mountains.

Deglacial ocean warming and marine margin retreat of the Cordilleran Ice Sheet in the North Pacific Ocean

“…Modern temperate tidewater glaciers that lose volume during thinning retreat rapidly from their marine margins (Hunter and Powell, 1998;Motyka et al, 2003), yet the CIS maintained a marine margin for nearly 2 ka from ∼19 to 17 ka. We argue that there were two important features of the CIS that prevented substantial retreat before 17.2 ka: the presence of morainal shoals (Herzer and Bornhold, 1982) and a significant supply of ice from the Coast Mountains (Margold et al, 2013b).…”

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

“…5;Fulton, 1967); and in eastcentral British Columbia, it retreated west and west-southwest back towards the Coast Mountains ( Fig. 6; Margold et al, 2013).…”

Subglacial drainage patterns of Devon Island, Canada: detailed comparison of rivers and subglacial meltwater channels

“…Along with the distinction from river systems, it is relevant to distinguish subglacial channels from channels formed by meltwater accumulated and released at the ice margins, i.e., lateral meltwater channels (e.g., Greenwood et al, 2007;Syverson and Mickelson, 2009;Margold et al, 2013), which have also been identified in the area (Dyke, 1999). We follow the criteria presented in Table 1, Greenwood et al (2007), to this end.…”

“…Although subglacial channels have been described in detail in the field in northern Europe (e.g., Kleman, 1992;Clark et al, 2004;Piotrowski et al, 2006), the Antarctica Dry Valleys (e.g., Denton et al, 1984;Sugden et al, 1991), Canada (e.g., Kor et al, 1991;Beaney and Shaw, 2000;Shaw, 2002), and the United States (e.g., Walder and Hallet, 1979;Booth and Hallet, 1993), the number of studies addressing their identification from other systems from remote sensing data is limited (Greenwood et al, 2007). Field identification of subglacial channels consists of (1) identification from fluvial runoff (proglacial channels or river systems) and (2) distinction from other meltwater features, primarily lateral meltwater channels (e.g., Beaney and Shaw, 2000;Greenwood et al, 2007;Syverson and Mickelson, 2009;Margold et al, 2013). A set of subglacial channel identification criteria is presented by Greenwood et al (2007) and summarized in Table 1.…”