Summit Station, Greenland

A camp for a deep core

Summit Station was established in April 1989 for the Greenland Ice Sheet Project Two (GISP2), an American ice-core drilling project at the highest point of the ice sheet. A European project, GRIP, drilled a second core about 30 kilometres away, so the two could be compared. GISP2 reached bedrock on 1 July 1993, after drilling 3,053 metres of ice.

The ice at the bottom is more than 100,000 years old. The cores recorded temperature through the isotopes of the ice, snowfall through the layers, and the atmosphere through bubbles of trapped air.

Abrupt change

The cores showed that during the last ice age, the climate of Greenland repeatedly switched within decades between cold and mild states, the Dansgaard–Oeschger events, a finding that changed the idea that climate always changes slowly. The cores also hold the record of the greenhouse gases of the past and the changes in volcanic and industrial aerosols.

The station stayed on. After the drilling it became a year-round observatory: the first experimental winter was in 1997, it was named the Greenland Environmental Observatory at Summit (GEOSummit) in 1999, and continuous occupation began in 2003.

A monitor of the ice sheet

Summit is now one of the cleanest and highest sites in the Arctic, used for measurements of atmospheric chemistry, snow, radiation and clouds. On 14 August 2021, rain fell for a whole day at the summit, the first liquid precipitation recorded there, and a sign of how warm air now reaches the highest part of the ice sheet. The US National Science Foundation funds the station and its science.

Cores, climate and caution

Ice cores are a one-time harvest: once the ice has been drilled and cut, it cannot be sampled again, so each core is divided among laboratories and archived at low temperature for future methods. The Summit cores gave scientists their first detailed view of abrupt climate change, and later research has refined the dates and the interpretation. The station's year-round operation now adds a modern record of the atmosphere above the ice sheet. A permanent presence is expensive, and it exists because the questions asked of the ice sheet, about melt, snowfall and sea level, are of high public interest.

Instruments and technologies

• Deep ice drill An electromechanical drill cut cylinders of ice a few metres long, brought up in sections, in a fluid-filled hole.
• Snow and atmosphere instruments Radiation, snow chemistry, cloud and aerosol instruments operate year round.
• Weather station A tall mast of sensors measures the profile of wind and temperature near the surface.

Timeline

• 1989 Station established in April for GISP2.
• 1993 GISP2 reaches bedrock on 1 July after 3,053 m of core.
• 1997 First experimental winter season.
• 1999 Named the Greenland Environmental Observatory at Summit (GEOSummit).
• 2003 Continuous year-round occupation begins.
• 2021 Rain falls all day on 14 August, the first liquid precipitation recorded at the summit.

Key lessons for observation today

• Two cores are better than one The parallel European and American cores let the teams check each other. Independent replicates catch errors.
• A project station can become an observatory GISP2 ended but the camp stayed and became a permanent site. Infrastructure built for one purpose can serve many.
• Record the first of a kind The first rain at the summit was recorded because an observatory was there. Permanent observation is how the first event is noticed.

Sources

• GEOSummit, Summit Station
• Wikipedia, Summit Camp
• NSF Office of Polar Programs
• Wikipedia, Greenland Ice Sheet Project (a pointer to the GISP2 papers)