In autumn 1988, the European Science Foundation agreed to fund a new European glaciology program and selected the Greenland Ice Core Project (GRIP) as its first major effort. GRIP’s goal was to drill and analyze a deep ice core from central Greenland to study climate and environmental changes over roughly 250,000 years. This created a coordinated European counterpart to the U.S.-led GISP2 project.
The U.S. National Science Foundation’s Office of Polar Programs officially initiated the Greenland Ice Sheet Project Two (GISP2). This set the stage for deep drilling near the top of the Greenland ice sheet to recover a long climate record from ice layers built up over many thousands of years. It also helped trigger parallel planning for a European deep-core effort at a nearby site.
In 1989, the GRIP steering committee sought additional funding from the European Commission under the EPOCH programme to fill gaps left by national funding. The support helped keep the project on schedule and enabled coordinated logistics and core analyses across many laboratories. This funding step mattered because deep ice-core drilling is expensive and time-sensitive, especially in remote polar conditions.
In 1989, U.S. teams began building the GISP2 drill camp near the Greenland ice-sheet summit, and GRIP began fieldwork at the nearby Summit location. Creating reliable camp infrastructure (power, shelter, and drilling space) was essential because drilling and handling ice cores requires stable cold conditions and careful logistics. The Summit area then became the central hub for both projects’ deep drilling.
GRIP began deep drilling in the summer 1990 field season using a purpose-built drill system, with drilling continuing in subsequent summer seasons. The project aimed to recover an ice core roughly 3 km long, with older ice generally found at greater depths. This work produced a high-resolution archive of past temperature and atmospheric changes recorded in the ice.
An EU-supported project associated with GRIP began in 1991 to study trace gases (such as methane and nitrous oxide) and relate them to carbon dioxide and climate signals in the core. Measuring gases trapped in ice bubbles helps reconstruct past atmospheric composition, not just temperature. This broadened GRIP’s impact by linking Greenland climate changes to global greenhouse-gas history.
On July 12, 1992, GRIP drilling stopped close to bedrock at a depth of 3028.8 meters after encountering gravel and stones that damaged the drill’s cutting parts. The project recovered deep basal ice, including debris-rich layers near the bottom. Reaching this depth was a major milestone because it provided a very long climate record and enabled comparisons with the nearby U.S. core.
In April 1993, GRIP and GISP2 organizers held a joint workshop (Annecy, France) to coordinate analysis plans and interpret results together. This mattered because the strongest conclusions depended on carefully aligning timescales, measurement methods, and uncertainty estimates across the two projects. Cooperation also reduced duplication and helped focus effort on the most important comparisons.
After deep drilling ended, GRIP used the 1993 field season to log the borehole for temperature and geometry (such as inclination and diameter) and to collect additional shallow cores. These measurements help scientists interpret the core correctly, because ice flow and heat affect how layers compress and deform over time. The work also supported cross-project comparisons with GISP2 by improving site characterization.
On July 1, 1993, GISP2 reached bedrock at 3053.44 meters depth after five years of drilling seasons, recovering the deepest ice core at that time. The GRIP and GISP2 drill sites were only a few tens of kilometers apart, which made direct record comparisons possible. This pairing was crucial for testing whether climate signals were regional and real—or artifacts of ice deformation near the base.
In July 1993, GRIP researchers published a widely cited Nature paper showing strong evidence of abrupt climate shifts in the Greenland record over a ~250,000-year span. A companion GRIP paper also argued that the last interglacial period in Greenland showed instability, based on isotope and chemical signals. These publications helped move “rapid climate change” from a niche idea to a central research question.
In December 1993, a Nature paper compared oxygen-isotope records from the GRIP and GISP2 cores. Comparing isotope signals is a basic way to check whether two nearby cores record the same temperature-related patterns through time. Reported differences, especially deeper in the cores, strengthened the case that basal ice can be disturbed by folding and mixing, limiting straightforward interpretation of the oldest sections.
GRIP’s final field season in 1995 included limited field activities and joint U.S.–European measurements of the GRIP and GISP2 drill holes. This work supported longer-term data quality by improving knowledge of borehole conditions and ice-sheet properties near the drill sites. It also marked the transition from intensive field operations to long-term laboratory analysis and data synthesis.
In September 1995, a second joint GRIP–GISP2 workshop (Wolfeboro, New Hampshire) helped wrap up GRIP’s official program phase and plan comprehensive publications. By this point, the projects had moved from “getting the ice” to building shared interpretations from many lab measurements (chemistry, isotopes, particles, and trapped gases). The workshop also helped formalize rules for continued use of remaining archived ice sections.
After the deep drilling campaigns, Summit remained a key research location rather than being abandoned. The site’s infrastructure and scientific importance helped it evolve from a seasonal drilling camp into a platform for broader, long-term climate and atmosphere studies. This transition built a lasting legacy from GRIP and GISP2 beyond the original ice-core recovery goals.
GRIP and GISP2 Greenland ice-core drilling projects (1989–1997)