U.S. Department of Energy Office of Scientific and Technical Information
The collapse of the Cordilleran–Laurentide ice saddle and early opening of the Mackenzie Valley, Northwest Territories, Canada, constrained by 10Be exposure dating
Deglaciation of the northwestern Laurentide Ice Sheet in the central Mackenzie Valley opened the northern portion of the deglacial Ice-Free Corridor between the Laurentide and Cordilleran ice sheets and a drainage route to the Arctic Ocean. In addition, ice sheet saddle collapse in this section of the Laurentide Ice Sheet has been implicated as a mechanism for delivering substantial freshwater influx into the Arctic Ocean on centennial timescales. However, there is little empirical data to constrain the deglaciation chronology in the central Mackenzie Valley where the northern slopes of the ice saddle were located. Here, we present 30 new 10Be cosmogenic nuclide exposure dates across six sites, including two elevation transects, which constrain the timing and rate of thinning and retreat of the Laurentide Ice Sheet in the area. Our new 10Be dates indicate that the initial deglaciation of the eastern summits of the central Mackenzie Mountains began at ~15.8 ka (17.1–14.6 ka), ~1000 years earlier than in previous reconstructions. The main phase of ice saddle collapse occurred between ~14.9 and 13.6 ka, consistent with numerical modelling simulations, placing this event within the Bølling–Allerød interval (14.6–12.9 ka). Our new dates require a revision of ice margin retreat dynamics, with ice retreating more easterly rather than southward along the Mackenzie Valley. In addition, we quantify a total sea level rise contribution from the Cordilleran–Laurentide ice saddle region of ~11.2 m between 16 and 13 ka.
Stoker, Benjamin J., et al. "The collapse of the Cordilleran–Laurentide ice saddle and early opening of the Mackenzie Valley, Northwest Territories, Canada, constrained by <sup>10</sup>Be exposure dating." The Cryosphere (Online), vol. 16, no. 12, Dec. 2022. https://doi.org/10.5194/tc-16-4865-2022
Stoker, Benjamin J., Margold, Martin, Gosse, John C., Hidy, Alan J., Monteath, Alistair J., Young, Joseph M., Gandy, Niall, Gregoire, Lauren J., Norris, Sophie L., & Froese, Duane (2022). The collapse of the Cordilleran–Laurentide ice saddle and early opening of the Mackenzie Valley, Northwest Territories, Canada, constrained by <sup>10</sup>Be exposure dating. The Cryosphere (Online), 16(12). https://doi.org/10.5194/tc-16-4865-2022
Stoker, Benjamin J., Margold, Martin, Gosse, John C., et al., "The collapse of the Cordilleran–Laurentide ice saddle and early opening of the Mackenzie Valley, Northwest Territories, Canada, constrained by <sup>10</sup>Be exposure dating," The Cryosphere (Online) 16, no. 12 (2022), https://doi.org/10.5194/tc-16-4865-2022
@article{osti_1902605,
author = {Stoker, Benjamin J. and Margold, Martin and Gosse, John C. and Hidy, Alan J. and Monteath, Alistair J. and Young, Joseph M. and Gandy, Niall and Gregoire, Lauren J. and Norris, Sophie L. and Froese, Duane},
title = {The collapse of the Cordilleran–Laurentide ice saddle and early opening of the Mackenzie Valley, Northwest Territories, Canada, constrained by <sup>10</sup>Be exposure dating},
annote = {Deglaciation of the northwestern Laurentide Ice Sheet in the central Mackenzie Valley opened the northern portion of the deglacial Ice-Free Corridor between the Laurentide and Cordilleran ice sheets and a drainage route to the Arctic Ocean. In addition, ice sheet saddle collapse in this section of the Laurentide Ice Sheet has been implicated as a mechanism for delivering substantial freshwater influx into the Arctic Ocean on centennial timescales. However, there is little empirical data to constrain the deglaciation chronology in the central Mackenzie Valley where the northern slopes of the ice saddle were located. Here, we present 30 new 10Be cosmogenic nuclide exposure dates across six sites, including two elevation transects, which constrain the timing and rate of thinning and retreat of the Laurentide Ice Sheet in the area. Our new 10Be dates indicate that the initial deglaciation of the eastern summits of the central Mackenzie Mountains began at ~15.8 ka (17.1–14.6 ka), ~1000 years earlier than in previous reconstructions. The main phase of ice saddle collapse occurred between ~14.9 and 13.6 ka, consistent with numerical modelling simulations, placing this event within the Bølling–Allerød interval (14.6–12.9 ka). Our new dates require a revision of ice margin retreat dynamics, with ice retreating more easterly rather than southward along the Mackenzie Valley. In addition, we quantify a total sea level rise contribution from the Cordilleran–Laurentide ice saddle region of ~11.2 m between 16 and 13 ka.},
doi = {10.5194/tc-16-4865-2022},
url = {https://www.osti.gov/biblio/1902605},
journal = {The Cryosphere (Online)},
issn = {ISSN 1994-0424},
number = {12},
volume = {16},
place = {United States},
publisher = {Copernicus Publications, EGU},
year = {2022},
month = {12}}
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Organization:
Charles University Grant Agency; Czech Science Foundation; NRCan Polar Continental Shelf Program; National Science Foundation (NSF); Natural Science and Engineering Research Council; Swedish Research Council; USDOE National Nuclear Security Administration (NNSA); University of Alberta
Grant/Contract Number:
AC52-07NA27344
OSTI ID:
1902605
Report Number(s):
LLNL-JRNL-778009; 972084
Journal Information:
The Cryosphere (Online), Journal Name: The Cryosphere (Online) Journal Issue: 12 Vol. 16; ISSN 1994-0424