Dynamical response of the southwestern Laurentide Ice Sheet to rapid Bølling–Allerød warming
<p>The shift in climate that occurred between the Last Glacial Maximum (LGM) and the Early Holocene (ca. 18–12 kyr BP) displayed rates of temperature increase similar to present-day warming trends. The most rapid recorded changes in temperature occurred during the abrupt climate oscillations k...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2024-04-01
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| Series: | The Cryosphere |
| Online Access: | https://tc.copernicus.org/articles/18/1533/2024/tc-18-1533-2024.pdf |
| _version_ | 1797221567273369600 |
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| author | S. L. Norris S. L. Norris M. Margold D. J. A. Evans N. Atkinson D. G. Froese |
| author_facet | S. L. Norris S. L. Norris M. Margold D. J. A. Evans N. Atkinson D. G. Froese |
| author_sort | S. L. Norris |
| collection | DOAJ |
| description | <p>The shift in climate that occurred between the Last Glacial Maximum (LGM) and the Early Holocene (ca. 18–12 kyr BP) displayed rates of temperature increase similar to present-day warming trends. The most rapid recorded changes in temperature occurred during the abrupt climate oscillations known as the Bølling–Allerød interstadial (14.7–12.9 kyr BP) and the Younger Dryas stadial (12.9–11.7 kyr BP). Reconstructing ice sheet dynamics during these climate oscillations provides the opportunity to assess long-term ice sheet evolution in reaction to a rapidly changing climate. Here, we use glacial geomorphological inversion methods (flowsets) to reconstruct the ice flow dynamics and the marginal retreat pattern of the southwestern sector of the Laurentide Ice Sheet (SWLIS). We combine our reconstruction with a recently compiled regional deglaciation chronology to depict ice flow dynamics that encompass the time period from pre-LGM to the Early Holocene. Our reconstruction portrays three macroscale reorganizations in the orientation and dynamics of ice streaming followed by regional deglaciation associated with rapid warming during the Bølling–Allerød interstadial. Initial westward flow is documented, likely associated with an early set of ice streams that formed during the advance to the LGM. During the LGM ice streaming displays a dominant north to south orientation. Ice sheet thinning at <span class="inline-formula">∼15</span> ka is associated with a macroscale reorganization in ice stream flow, with a complex of ice streams recording south-eastward flow. A second macroscale reorganization in ice flow is then observed at <span class="inline-formula">∼14</span> ka, in which southwestern ice flow is restricted to the Hay, Peace, Athabasca, and Churchill river lowlands. Rates of ice sheet retreat then slowed considerably during the Younger Dryas stadial; at this time, the ice margin was situated north of the Canadian Shield boundary and ice flow continued to be sourced from the northeast. Resulting from these changes in ice sheet dynamics, we recognize a three-part pattern of deglacial landform zonation within the SWLIS characterized by active ice margin recession, stagnation and downwasting punctuated by local surging (terrestrial ice sheet collapse): the outer deglacial zone contains large recessional moraines aligned with the direction of active ice margin retreat; the intermediate deglacial zone contains large regions of hummocky and stagnation terrain, in some areas crosscut by the signature of local surges, reflecting punctuated stagnation and downwasting; and the inner deglacial zone contains inset recessional moraines demarcating progressive regional ice margin retreat. We attribute these macroscale changes in ice flow geometry and associated deglacial behaviour to external climatic controls during the Bølling–Allerød and Younger Dryas but also recognize the role of internal (glaciological, lithological and topographic) controls in SWLIS dynamics.</p> |
| first_indexed | 2024-04-24T13:07:29Z |
| format | Article |
| id | doaj.art-88941b1a88a14845a193d5c100d85319 |
| institution | Directory Open Access Journal |
| issn | 1994-0416 1994-0424 |
| language | English |
| last_indexed | 2024-04-24T13:07:29Z |
| publishDate | 2024-04-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | The Cryosphere |
| spelling | doaj.art-88941b1a88a14845a193d5c100d853192024-04-05T07:15:05ZengCopernicus PublicationsThe Cryosphere1994-04161994-04242024-04-01181533155910.5194/tc-18-1533-2024Dynamical response of the southwestern Laurentide Ice Sheet to rapid Bølling–Allerød warmingS. L. Norris0S. L. Norris1M. Margold2D. J. A. Evans3N. Atkinson4D. G. Froese5Department of Geography, University of Victoria, David Turpin Building, 3800 Finnerty Road, Victoria, BC, V9P 5C2, CanadaDepartment of Earth and Atmospheric Sciences, 1–26 Earth Sciences Building, University of Alberta, Edmonton, AB, T6G 2E3, CanadaDepartment of Physical Geography and Geoecology, Charles University, Albertov 6, 128 43 Prague 2, Czech RepublicDepartment of Geography, Durham University, South Road, Durham, DH1 3LE, United KingdomAlberta Geological Survey, Alberta Energy Regulator, 402 Twin Atria Building, 4 4999-98 Avenue, Edmonton, AB, T6B 2X3, CanadaDepartment of Earth and Atmospheric Sciences, 1–26 Earth Sciences Building, University of Alberta, Edmonton, AB, T6G 2E3, Canada<p>The shift in climate that occurred between the Last Glacial Maximum (LGM) and the Early Holocene (ca. 18–12 kyr BP) displayed rates of temperature increase similar to present-day warming trends. The most rapid recorded changes in temperature occurred during the abrupt climate oscillations known as the Bølling–Allerød interstadial (14.7–12.9 kyr BP) and the Younger Dryas stadial (12.9–11.7 kyr BP). Reconstructing ice sheet dynamics during these climate oscillations provides the opportunity to assess long-term ice sheet evolution in reaction to a rapidly changing climate. Here, we use glacial geomorphological inversion methods (flowsets) to reconstruct the ice flow dynamics and the marginal retreat pattern of the southwestern sector of the Laurentide Ice Sheet (SWLIS). We combine our reconstruction with a recently compiled regional deglaciation chronology to depict ice flow dynamics that encompass the time period from pre-LGM to the Early Holocene. Our reconstruction portrays three macroscale reorganizations in the orientation and dynamics of ice streaming followed by regional deglaciation associated with rapid warming during the Bølling–Allerød interstadial. Initial westward flow is documented, likely associated with an early set of ice streams that formed during the advance to the LGM. During the LGM ice streaming displays a dominant north to south orientation. Ice sheet thinning at <span class="inline-formula">∼15</span> ka is associated with a macroscale reorganization in ice stream flow, with a complex of ice streams recording south-eastward flow. A second macroscale reorganization in ice flow is then observed at <span class="inline-formula">∼14</span> ka, in which southwestern ice flow is restricted to the Hay, Peace, Athabasca, and Churchill river lowlands. Rates of ice sheet retreat then slowed considerably during the Younger Dryas stadial; at this time, the ice margin was situated north of the Canadian Shield boundary and ice flow continued to be sourced from the northeast. Resulting from these changes in ice sheet dynamics, we recognize a three-part pattern of deglacial landform zonation within the SWLIS characterized by active ice margin recession, stagnation and downwasting punctuated by local surging (terrestrial ice sheet collapse): the outer deglacial zone contains large recessional moraines aligned with the direction of active ice margin retreat; the intermediate deglacial zone contains large regions of hummocky and stagnation terrain, in some areas crosscut by the signature of local surges, reflecting punctuated stagnation and downwasting; and the inner deglacial zone contains inset recessional moraines demarcating progressive regional ice margin retreat. We attribute these macroscale changes in ice flow geometry and associated deglacial behaviour to external climatic controls during the Bølling–Allerød and Younger Dryas but also recognize the role of internal (glaciological, lithological and topographic) controls in SWLIS dynamics.</p>https://tc.copernicus.org/articles/18/1533/2024/tc-18-1533-2024.pdf |
| spellingShingle | S. L. Norris S. L. Norris M. Margold D. J. A. Evans N. Atkinson D. G. Froese Dynamical response of the southwestern Laurentide Ice Sheet to rapid Bølling–Allerød warming The Cryosphere |
| title | Dynamical response of the southwestern Laurentide Ice Sheet to rapid Bølling–Allerød warming |
| title_full | Dynamical response of the southwestern Laurentide Ice Sheet to rapid Bølling–Allerød warming |
| title_fullStr | Dynamical response of the southwestern Laurentide Ice Sheet to rapid Bølling–Allerød warming |
| title_full_unstemmed | Dynamical response of the southwestern Laurentide Ice Sheet to rapid Bølling–Allerød warming |
| title_short | Dynamical response of the southwestern Laurentide Ice Sheet to rapid Bølling–Allerød warming |
| title_sort | dynamical response of the southwestern laurentide ice sheet to rapid bolling allerod warming |
| url | https://tc.copernicus.org/articles/18/1533/2024/tc-18-1533-2024.pdf |
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