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| Titel |
The complex behavior of the Cordilleran Ice Sheet and mountain glaciers to abrupt climate change during the latest Pleistocene |
| VerfasserIn |
Brian Menounos, Brent Goehring, Gerald Osborn, Garry K. C. Clarke, Brent Ward, Martin Margold, Jeff Bond, John J. Clague, Tom Lakeman, Joerg Schaefer, Joe Koch, John Gosse, Arjen P. Stroeven, Julien Seguinot, Jakob Heyman, Robert Fulton |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250099255
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| Publikation (Nr.) |
 EGU/EGU2014-15013.pdf |
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| Zusammenfassung |
| Surficial mapping and more than 70 radiometric ages 10Be, 14C] constrain the evolution of
the Cordilleran Ice Sheet (CIS) and associated mountain glaciers in western Canada during
the latest Pleistocene. Our data suggest that: i) there is widespread evidence for the Younger
Dryas (YD) throughout the mountains of western Canada; ii) late Pleistocene climate
reconstructions based solely on alpine moraines may be misleading in regions with decaying
ice sheets; iii) extensive interfluves in some mountain regions were ice-free between 16 ka
and 13 ka (kilo calibrated yrs BP). Initial decay of the CIS from its maximum extent around
16 ka was likely due to a combination of climatic (surface melting) and dynamical factors.
Climate amelioration during the Bølling-Allerød Warm Period [14.7-12.9 ka], likely
the cause for the major phase of CIS decay, resulted in ice sheet equilibrium line
altitudes (ELAs) ranging from 2500 m asl in southern BC to around 2000 m asl along
the BC-Yukon border. Hence, before the onset of the Younger Dryas (YD) Cold
Period [12.9-11.7 ka], the ice sheet shrank and became a labyrinth of individual and
coalescing valley glaciers fed by major accumulation zones centered on the Coast
Mountains and other high ranges of NW Canada. The response of remnant ice and
cirque glaciers to the YD climate deterioration was highly variable. In some cases,
small glaciers (0.5-2 km2) built YD moraines that were only hundreds of meters
beyond those constructed during the Little Ice Age (LIA) [0.30-0.15 ka]. Our dating
also reveals that much larger glaciers persisted in nearby valleys that lie hundreds
of meters below the cirques. Hence, we infer that many cirques were completely
deglaciated prior the YD, in contrast to low-lying valleys where ice sheet remnants
persisted. Glaciers also advanced in north-central British Columbia during the YD,
but here glaciers constructed large terminal and lateral moraines. In the Cassiar
and northern Coast mountains, for example, 25 10Be [13.10-12.00 ka] and four
minimum-limiting 14C ages from lakes impounded by moraines show that glaciers existed
up to 10 km beyond LIA glacier limits during the YD. These glaciers thus had
ELAs that were 300-500 m lower than contemporary glaciers. We are currently
performing high-resolution ( |
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