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6. Dynamical response of the southwestern Laurentide Ice Sheet to rapid Bølling–Allerød warming.

Author

Norris, Sophie L., Margold, Martin, Evans, David J. A., Atkinson, Nigel, and Froese, Duane G.

Abstract

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 ∼15 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 ∼14 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. [ABSTRACT FROM AUTHOR]

Published
2024
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11. The Empress Group in Alberta, Canada.

Author

Hartman, Gregory M.D., Pawley, Steven M., Utting, Daniel J., Atkinson, Nigel, and Liggett, Jessica E.

Subjects
CANADIAN history, BEDROCK, MACHINE learning, GRAVEL, GLACIATION, TILLAGE
Abstract

Basal gravel and sand mantling the bedrock floors of buried valleys throughout the Canadian Interior Plains, and conformably overlying proglacial lacustrine sediment, comprise the Empress Group. While previously conceptualized as stratigraphically equivalent deposits of preglacial rivers prior to the first and most extensive continental and montane glaciations, subsequent stratigraphic studies indicated that buried valley basal gravel must have been deposited between, or during, progressively more extensive continental glaciations and could not be stratigraphically equivalent throughout the buried valley network. However, in the general absence of formation-rank stratigraphic description of basal gravel units that might better inform the geologic history of the deposits, most workers simply consider Empress Group sediments time-transgressive. In this paper, we examine basal gravel at provincial and regional scales to understand its genesis and geologic history. At the provincial scale, we map basal gravel in three dimensions using a novel machine learning approach. At the regional scale, we formally define basal gravel formations at either end of the largest buried valley system in Alberta, which informs its glacial history and physiographic development and shows the importance of formation-rank stratigraphic description. Our results indicate that the buried valley network across Alberta is palimpsest in genesis and basal gravel units within it are chronostratigraphically intercalated between tills. We advocate that the Empress Group definition be extended across Alberta with modifications to improve its clarity and utility, and formally define the Old Fort, Unchaga, Ipiatik, and Winefred formations as part of the Empress Group. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Alcohol‐induced aggression in Drosophila

Author

Park, Annie, primary, Tran, Tracy, additional, Gutierrez, Linda, additional, Stojanik, Christopher J., additional, Plyler, Julian, additional, Thompson, Grace A., additional, Bohm, Rudolf A., additional, Scheuerman, Elizabeth A., additional, Smith, Dean P., additional, and Atkinson, Nigel S., additional

Published
2021
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17. Supplementary material to "Ribbed bedforms in palaeo-ice streams reveal shear margin positions, lobe shutdown and the interaction of meltwater drainage and ice velocity patterns"

Author

Vérité, Jean, primary, Ravier, Édouard, additional, Bourgeois, Olivier, additional, Pochat, Stéphane, additional, Lelandais, Thomas, additional, Mourgues, Régis, additional, Clark, Christopher D., additional, Bessin, Paul, additional, Peigné, David, additional, and Atkinson, Nigel, additional

Published
2020
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18. Ribbed bedforms in palaeo-ice streams reveal shear margin positions, lobe shutdown and the interaction of meltwater drainage and ice velocity patterns

Author

Vérité, Jean, primary, Ravier, Édouard, additional, Bourgeois, Olivier, additional, Pochat, Stéphane, additional, Lelandais, Thomas, additional, Mourgues, Régis, additional, Clark, Christopher D., additional, Bessin, Paul, additional, Peigné, David, additional, and Atkinson, Nigel, additional

Published
2020
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25. An updated radiocarbon-based ice margin chronology for the last deglaciation of the North American Ice Sheet Complex

Author

Dalton, April S., primary, Margold, Martin, additional, Stokes, Chris R., additional, Tarasov, Lev, additional, Dyke, Arthur S., additional, Adams, Roberta S., additional, Allard, Serge, additional, Arends, Heather E., additional, Atkinson, Nigel, additional, Attig, John W., additional, Barnett, Peter J., additional, Barnett, Robert L., additional, Batterson, Martin, additional, Bernatchez, Pascal, additional, Borns, Harold W., additional, Breckenridge, Andy, additional, Briner, Jason P., additional, Brouard, Etienne, additional, Campbell, Janet E., additional, Carlson, Anders E., additional, Clague, John J., additional, Curry, B. Brandon, additional, Daigneault, Robert-André, additional, Dubé-Loubert, Hugo, additional, Easterbrook, Don J., additional, Franzi, David A., additional, Friedrich, Hannah G., additional, Funder, Svend, additional, Gauthier, Michelle S., additional, Gowan, Angela S., additional, Harris, Ken L., additional, Hétu, Bernard, additional, Hooyer, Tom S., additional, Jennings, Carrie E., additional, Johnson, Mark D., additional, Kehew, Alan E., additional, Kelley, Samuel E., additional, Kerr, Daniel, additional, King, Edward L., additional, Kjeldsen, Kristian K., additional, Knaeble, Alan R., additional, Lajeunesse, Patrick, additional, Lakeman, Thomas R., additional, Lamothe, Michel, additional, Larson, Phillip, additional, Lavoie, Martin, additional, Loope, Henry M., additional, Lowell, Thomas V., additional, Lusardi, Barbara A., additional, Manz, Lorraine, additional, McMartin, Isabelle, additional, Nixon, F. Chantel, additional, Occhietti, Serge, additional, Parkhill, Michael A., additional, Piper, David J.W., additional, Pronk, Antonius G., additional, Richard, Pierre J.H., additional, Ridge, John C., additional, Ross, Martin, additional, Roy, Martin, additional, Seaman, Allen, additional, Shaw, John, additional, Stea, Rudolph R., additional, Teller, James T., additional, Thompson, Woodrow B., additional, Thorleifson, L. Harvey, additional, Utting, Daniel J., additional, Veillette, Jean J., additional, Ward, Brent C., additional, Weddle, Thomas K., additional, and Wright, Herbert E., additional

Published
2020
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30. Alcohol Increases Aggression in Flies

Author

Park, Annie, primary, Tran, Tracy, additional, Scheuermann, Elizabeth, additional, Gutierrez, Linda, additional, Stojanik, Christopher, additional, Plyler, Julian, additional, Thompson, Grace, additional, Smith, Dean, additional, and Atkinson, Nigel S., additional

Published
2019
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31. Dynamical response of the southwestern Laurentide Ice Sheet to rapid Bølling-Allerød warming

Author

Norris, Sophie L., Margold, Martin, Evans, David J. A., Atkinson, Nigel, and Froese, Duane G.

Abstract

The climatic transition from the Last Glacial Maximum (LGM) to the early Holocene (ca. 18–12 ka BP) involved rates of temperature change comparable with 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 ka BP) and the Younger Dryas stadial (12.9–11.7 ka BP). Accurate reconstructions of ice sheet behaviour during these climate oscillations provide the opportunity to assess long-term ice sheet evolution in reaction to a rapidly changing climate. Here, we use glacial geomorphological inverse methods (flowsets) to reconstruct the ice flow dynamics associated with changes in ice stream catchments (ice divides and domes) and the marginal retreat pattern of the southwestern sector of the Laurentide Ice Sheet (SWLIS). We combine this ice dynamic reconstruction with a recently compiled regional deglaciation chronology to present a model of ice sheet behaviour spanning pre-LGM to the early Holocene. Our reconstruction depicts rapid ice geometry changes, including three macroscale reorganizations of the ice drainage network followed by regional deglaciation synchronous with abrupt warming during the Bølling-Allerød interstadial. Initial westward flow is documented, most probably associated with an evolving ice stream network during the advance to the LGM. Ice streaming at the LGM was marked by southward flows, unconstrained by topography. Following this, a significant switch in the ice sheets dynamics occurred at ~15 ka BP to topographically controlled south-eastward flow constrained by preglacial-valley systems. This was replaced by a second switch in ice flow orientation to the southwest at ~14.5 ka BP. 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 pattern of deglacial landform zonation within the SWLIS characterized by active ice margin recession and ice sheet stagnation and downwasting punctuated by local surging (terrestrial ice sheet collapse): (1) the outer deglacial zone is characterized by large recessional moraines aligned with the direction of active ice margin retreat; (2) the intermediate deglacial zone contains large regions of hummocky and stagnation terrain, in some areas overprinted by the signature of local surges, reflecting punctuated stagnation and downwasting and; (3) the inner deglacial zone comprises inset recessional moraines demarcating progressive regional ice margin retreat. We attribute these macroscale changes in ice flow geometry and the associated deglacial behaviour to external climatic forcing during the Bølling-Allerød and Younger Dryas but also recognize the role of internal (glaciological, lithological and topographic) controls.

Published
2023

32. The Role of Toll and Nonnuclear NF-κB Signaling in the Response to Alcohol.

Author

Atkinson, Nigel S.

Subjects
ALCOHOL, ALCOHOLISM, NEUROTROPHIN receptors, DROSOPHILA, NERVOUS system, CELLULAR signal transduction, TOLL-like receptors, TOLLS, DRUNK driving
Abstract

An understanding of neuroimmune signaling has become central to a description of how alcohol causes addiction and how it damages people with an AUD. It is well known that the neuroimmune system influences neural activity via changes in gene expression. This review discusses the roles played by CNS Toll-like receptor (TLR) signaling in the response to alcohol. Also discussed are observations in Drosophila that show how TLR signaling pathways can be co-opted by the nervous system and potentially shape behavior to a far greater extent and in ways different than generally recognized. For example, in Drosophila, TLRs substitute for neurotrophin receptors and an NF-κB at the end of a TLR pathway influences alcohol responsivity by acting non-genomically. [ABSTRACT FROM AUTHOR]

Published
2023
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34. Microbiota-dependent elevation of Alcohol Dehydrogenase inDrosophilais associated with changes in alcohol-induced hyperactivity and alcohol preference

Author

Blundon, Malachi A., primary, Park, Annie, additional, Keith, Scott A., additional, Oliver, Stacie L., additional, Eutsey, Rory A., additional, Pyzel, Anna M., additional, Lau, Tiffany W., additional, Huang, Jennifer H., additional, Kolev, Hannah M., additional, Luisa Hiller, N., additional, Atkinson, Nigel S., additional, Minden, Jonathan S., additional, and McCartney, Brooke M., additional

Published
2018
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38. The periodic topography of ice stream beds: Insights from the Fourier spectra of mega‐scale glacial lineations

Author

Spagnolo, Matteo, primary, Bartholomaus, Timothy C., additional, Clark, Chris D., additional, Stokes, Chris R., additional, Atkinson, Nigel, additional, Dowdeswell, Julian A., additional, Ely, Jeremy C., additional, Graham, Alastair G. C., additional, Hogan, Kelly A., additional, King, Edward C., additional, Larter, Robert D., additional, Livingstone, Stephen J., additional, and Pritchard, Hamish D., additional

Published
2017
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