Early Pleistocene Glacier Ice Preserved in Permafrost in the Eastern Canadian Arctic

Academic Background

Permafrost is a crucial paleoenvironmental archive on Earth, capable of preserving valuable information such as fossils, plant remains, organic materials, and ancient DNA. In recent years, scientists have discovered that the preservation of glacier ice within permafrost can provide important clues for studying the morphology, stability, and paleoecosystems of ancient glaciers. However, despite extensive research on late Pleistocene permafrost and ground ice in the Arctic, reports on early Pleistocene glacier ice are extremely rare. This research gap limits our understanding of earlier glacial activities in the Arctic region.

Bylot Island in the eastern Canadian Arctic is a significant research site, with its plateau regions preserving glacial deposits from multiple ice ages. However, evidence of early Pleistocene glacial activity in this area has been lacking. This study aims to reveal the origin, age, and paleoenvironmental significance of early Pleistocene glacier ice preserved in the permafrost of Bylot Island through multidisciplinary approaches.

Source of the Paper

This paper was authored by Stéphanie Coulombe and colleagues, with the research team affiliated with Polar Knowledge Canada, Université de Montréal, Université Laval, University of Ottawa, and Université du Québec à Rimouski. The paper was published online on October 3, 2024, in the journal Geology, titled Early Pleistocene glacier ice preserved in permafrost in the eastern Canadian Arctic.

Research Process

1. Study Site and Sample Collection

The study site is located on the southwestern plateau of Bylot Island (approximately 500 meters above sea level). Researchers discovered two massive ground-ice bodies (BGI-1 and BGI-2) in the headwalls of thaw slumps at the edge of the plateau. The BGI-2 ice body was exposed in 2009, and ice crystallography samples were collected. The BGI-1 ice body was sampled in 2011, with three ice cores collected.

2. Determining the Origin and Age of the Ice Bodies

To determine the origin and age of the ice bodies, researchers employed multiple analytical methods: - Ice Structure Analysis: Ice crystallography, sediment distribution within the ice, and the contact relationship between the ice and surrounding sediments were used to infer the formation mechanism of the ice. - Isotope Analysis: The δ18O and δD isotope values of the ice were measured to infer the environmental conditions during ice formation. - Sediment Analysis: Grain-size distribution, diatom, and pollen analyses of the overlying sediments were conducted to determine the depositional environment. - Radiocarbon Dating: Radiocarbon dating was performed on dissolved organic carbon (DOC) in the ice and marine shells in the overlying sediments. - Paleomagnetic Measurements: Paleomagnetic measurements of the overlying sediments were conducted to determine their age.

3. Results and Discussion

Glacial Origin of the Ice Bodies

The ice bodies exhibited a layered structure, with alternating debris-rich and debris-poor ice layers. Suspended ice structures, gravel-sized erratic clasts, and millimeter-thick silt layers were also observed within the ice. These features are similar to those found in contemporary glacier ice, suggesting a glacial origin. Additionally, the low δ18O values of the ice further support the hypothesis of a glacial origin.

Age of the Ice Bodies

The overlying sediments recorded a normal-reverse-normal paleomagnetic polarity sequence, indicating that the sediments are at least 0.773 million years old (Ma). Radiocarbon dating of DOC in the ice yielded an age of 39,435 ± 1,810 years, but due to contamination by modern DOC, researchers believe the actual age of the ice may be older. Combining paleomagnetic data, the researchers inferred that the ice is at least 0.773 Ma old, and possibly even older.

Mechanisms of Long-Term Preservation

The preservation of the ice through multiple glacial cycles suggests that the plateau region may have been covered by cold-based ice during glacial periods, which has minimal erosive effects on the surface, thereby protecting older glacial deposits. Additionally, the permafrost conditions on the plateau (average ground temperature of -11°C from 2001 to 2022) and the thickness of the overlying sediments (approximately 3 meters) provided favorable conditions for the long-term preservation of the ice.

Research Conclusions

Through multidisciplinary approaches, this study has, for the first time, identified evidence of early Pleistocene glacier ice preserved in the permafrost of Bylot Island. The ice is at least 0.773 Ma old, and possibly even older, making it the oldest known glacier ice preserved in Arctic permafrost. This discovery not only reveals glacial activity on Bylot Island during the early Pleistocene but also provides important insights into paleoclimate and paleoenvironmental changes in the Arctic.

Research Highlights

1. Significant Scientific Discovery: This study is the first to identify evidence of early Pleistocene glacier ice preserved in Arctic permafrost, filling a research gap in early Pleistocene glacial activity in the region.
2. Integration of Multidisciplinary Methods: The study employed ice crystallography, isotope analysis, sediment analysis, radiocarbon dating, and paleomagnetic measurements, providing comprehensive evidence for the origin and age of the ice.
3. Revealing Long-Term Preservation Mechanisms: The study highlights the protective role of cold-based ice on the plateau and the importance of permafrost conditions for the long-term preservation of the ice.
4. Warning on Climate Change: With ongoing climate warming, these ancient glacier ice bodies are at risk of melting, reminding us to pay attention to the stability of Arctic permafrost and its response to global climate change.

Research Value

This study not only provides new evidence for early Pleistocene glacial activity in the Arctic but also offers important references for understanding the response mechanisms of permafrost to climate change. Additionally, the findings remind us that, with global warming, Arctic permafrost and glacier ice are facing significant degradation risks, which could have profound impacts on global climate systems and ecosystems.