A new study from the GreenDrill project reports that the Prudhoe Dome ice cap, a component of the Greenland Ice Sheet, was entirely absent approximately 7,000 years ago. This finding, published on January 5 in Nature Geoscience, suggests that this high-elevation area in the northwest section of the ice sheet is sensitive to the relatively mild temperatures characteristic of the Holocene period, an interglacial period that began 11,000 years ago and continues today.
Key Findings
The research indicates that the melting and subsequent retreat of Prudhoe Dome occurred during the natural climate changes of the early Holocene. Lead author Caleb Walcott-George, assistant professor at the University of Kentucky, noted that this timeframe suggests the dome melted prior to the period of 6,000 to 8,200 years ago, likely during the early Holocene when temperatures were estimated to be 3 to 5 degrees Celsius warmer than current levels. Projections suggest that similar warming levels could occur at Prudhoe Dome by the year 2100.
Jason Briner, a professor at the University at Buffalo and GreenDrill co-leader, commented that the dome's past retreat during mild climate conditions suggests a potential for future retreat under contemporary climate change conditions. Joerg Schaefer, a research professor at Columbia University’s Lamont-Doherty Earth Observatory and GreenDrill co-leader, emphasized that direct observations from rock and sediment beneath the ice sheet provide insights into the most vulnerable margins of the ice sheet.
Research Methodology
The GreenDrill project is an initiative funded by the U.S. National Science Foundation, established to extract bedrock and sediment samples from beneath the Greenland Ice Sheet. This inaugural study analyzed core samples obtained in 2023 from a depth of 1,669 feet below the surface at the summit of Prudhoe Dome.
Researchers applied luminescence dating to the sediment. This method measures trapped electrons in mineral grains, which are released as light upon exposure to daylight, indicating the last time the sediment was exposed to the surface. Analysis of these samples revealed that the Prudhoe Dome sediment was last exposed to daylight between 6,000 and 8,200 years ago.
Implications
The findings contribute to the understanding of sea level rise by identifying vulnerable regions at the ice sheet's edge. This information can assist scientists in anticipating where the ice sheet may melt first, which is relevant for localized sea level predictions and assessing potential risks to coastal communities.
Project Operations and Future Directions
The GreenDrill team established two drill sites on Prudhoe Dome: one at the summit, from which the samples for this study were taken, and another near the ice edge, where the ice is thinner. These sites were located near Camp Century, a Cold War-era base.
During operations in the spring of 2023, daily activities included collecting ice chips from drilling fluid and clearing snow. A technical challenge involving a fracture in the ice at the summit site during the final drilling stage was addressed by using a drill bit typically employed for rocks. Key collaborators on the project included Nicolás Young, Allie Balter-Kennedy, and Nathan Brown.
The project demonstrated the logistical feasibility and technological capability to drill to bedrock and analyze the retrieved material. The GreenDrill team anticipates producing additional studies from the collected samples, including the core from the ice edge site. Researchers also plan to investigate plant traces within the samples, which may offer information about Greenland’s ancient environment. The project aims to provide observational data to validate and enhance numerical models that predict ice melt rates.