Direct observations of the Greenland Ice Sheet (GrIS) size during Quaternary interglaciations are sparse, yet needed for testing numerical models of ice sheet history and sea level contributions. Recent measurements of cosmogenic nuclides in subglacial bedrock beneath Summit, Greenland, reveal that the ice sheet likely did not survive some interglacials in the past million years.
GreenDrill aims to retrieve additional bedrock cores from beneath the GrIS primarily for cosmogenic nuclide analysis. More information from the bed will be used to constrain ice sheet contribution to sea level rise during past interglacials.
The U.S. Ice Drilling Program is a critical partner in our work. In deciding where to drill, we are bounded by a set of criteria.
- Currently available drills from the U.S. Ice Drilling Program require <700 m ice thickness, limiting us to 15.4% of the GrIS, and frozen-bedded conditions, limiting us to 37.8% of the GrIS (using MacGregor BTS v2). Combining these two criteria limits us to 6.9% of the GrIS.
- Safety is a primary concern and crevasses are a concern. Areas with cresasses >0.005/yr strain rate further limit the options to 4.9% of the GrIS (based on Poinar & Andrews, 2021).
- Ideal for a choice suite of cosmogenic nuclides, we also seek quartz-bearing lithologies limiting us to 3.9% of the GrIS.
- And finally, we consider the results from the modeling ensemble runs.
These and other requirements conspire to make available only a very small portion of the GrIS footprint as drilling targets using current technology.
We have identified locations beneath the GrIS that are best suited for drilling including sites bordering Inglefield Land in northwestern Greenland, near Victoria Fjord and Mylius-Erichsen Land in northern Greenland, and inland from the alpine topography along the ice margin in eastern and northeastern Greenland.
There are critical layers of information required to meet both technological and scientific objectives. Significant logistical support by the US National Science Foundation is secured for GreenDrill. This also serves as an invitation for other scientists to capitalize on the National Science Foundation’s logistical support of GreenDrill to support their studies. Boreholes to the bed, sections of basal ice, drill-site basecamps and traverse vehicles, and en-route traversing across North Greenland are some examples of what could potentially become available for use.