Preprints
https://doi.org/10.5194/egusphere-2024-2091
https://doi.org/10.5194/egusphere-2024-2091
19 Jul 2024
 | 19 Jul 2024

Ice sheet model simulations reveal polythermal ice conditions existed across the NE USA during the Last Glacial Maximum

Joshua Cuzzone, Aaron Barth, Kelsey Barker, and Mathieu Morlighem

Abstract. Geologic evidence of the Laurentide Ice Sheet (LIS) provides abundant constraints on the areal extent of the ice sheet during the Last Glacial Maximum (LGM). Direct observations of LGM LIS thickness are non-existent, however, with most geologic data across high elevation summits in the Northeastern United States (NE USA) often showing signs of inheritance, indicative of weakly erosive ice flow and the presence of cold-based ice. While warm-based ice and erosive conditions likely existed on the flanks of these summits and throughout neighboring valleys, summit inheritance issues have hampered efforts to constrain the timing of the emergence of ice-free conditions at high elevation summits. These geomorphic reconstructions indicate that a complex erosional and thermal regime likely existed across the southeasternmost extent of the LIS sometime during the LGM, although this has not been confirmed by ice sheet models. Instead, current ice sheet models simulate warm-based ice conditions across this region, with disagreement likely arising from the use of low resolution meshes (e.g., >20 km) which are unable to resolve the high bedrock relief across this region that strongly influenced overall ice flow and the complex LIS thermal state. Here we use a newer generation ice sheet model, the Ice-sheet and Sea-level System Model (ISSM), to simulate the LGM conditions of the LIS across the NE USA and at 3 localities with high bedrock relief (Adirondack Mountains, White Mountains, and Mount Katahdin), with results confirming the existence of a complex thermal regime as interpreted by the geologic data. The model uses higher-order physics, a small ensemble of LGM climate boundary conditions, and a high-resolution horizontal mesh that resolves bedrock features down to 30 meters to reconstruct LGM ice flow, ice thickness, and thermal conditions. These results indicate that across the NE USA, polythermal conditions existed during the LGM. While the majority of this domain is simulated to be warm-based, cold-based ice persists where ice velocities are slow (<15 m/yr) particularly across regional ice divides (e.g., Adirondacks). Additionally, sharp thermal boundaries are simulated where cold-based ice across high elevation summits (White Mountains and Mount Katahdin) flank warm-based ice in adjacent valleys. Because geologic data is geographically limited, these high-resolution simulations can help fill gaps in our understanding of the geographical distribution of the polythermal ice during the LGM. We find that the elevation of this simulated thermal boundary ranges between 800–1500 meters, largely supporting geologic interpretations that polythermal ice conditions existed across NE USA during the LGM, however this boundary varies geographically. In general, we show that a model with finer spatial resolution and higher order physics is able to simulate the polythermal conditions captured in the geologic data, with model output being of potential utility for site selection in future geologic studies and geomorphic interpretation of landscape evolution.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Joshua Cuzzone, Aaron Barth, Kelsey Barker, and Mathieu Morlighem

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2091', Niall Gandy, 20 Aug 2024
  • RC2: 'Comment on egusphere-2024-2091', Paul Bierman, 16 Oct 2024
Joshua Cuzzone, Aaron Barth, Kelsey Barker, and Mathieu Morlighem

Data sets

Cuzzone2024: Ice sheet model simulations reveal polythermal ice conditions existed across the NE USA during the Last Glacial Maximum Joshua Cuzzone https://zenodo.org/records/12665418

Joshua Cuzzone, Aaron Barth, Kelsey Barker, and Mathieu Morlighem

Viewed

Total article views: 361 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
262 77 22 361 33 15 14
  • HTML: 262
  • PDF: 77
  • XML: 22
  • Total: 361
  • Supplement: 33
  • BibTeX: 15
  • EndNote: 14
Views and downloads (calculated since 19 Jul 2024)
Cumulative views and downloads (calculated since 19 Jul 2024)

Viewed (geographical distribution)

Total article views: 359 (including HTML, PDF, and XML) Thereof 359 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 08 Dec 2024
Download
Short summary
We use an ice sheet model to simulate the Last Glacial Maximum conditions of the Laurentide Ice Sheet (LIS) across the Northeast United States. A complex thermal history existed for the (LIS), that allowed for high erosion across most of the NE USA, but prevented erosion across high elevation mountain peaks and areas where ice flow was slow. This has implications for geologic studies which rely on the erosional nature of the LIS to reconstruct its glacial history and landscape evolution.