Ice core drilling on Greenland reaches bedrock

The first results, still reported by the team from Greenland, are extraordinary: The ice stream flows like a river of ice, tearing itself away from the surrounding, slowly flowing ice sheet. It could be determined that the entire ice mass of 2670 metres thickness flows like an expanding block at a speed of 58 metres per year. The ice block moves on a layer of wet mud, which must act like a quicksand layer that allows the ice block to flow over the rock. Near the bottom of the ice, the team found rocks and sand embedded in the ice. The ice itself near the base is more than 120 000 years old and dates from the last warm interglacial period, when temperatures over Greenland were 5 degrees Celsius warmer than today. Greenland's ice streams provide the ocean with nutrients that are important for fisheries, among other things. The future of the ice streams is therefore of great importance for Greenland.

The story of the EGRIP project

The first ice cores were drilled exactly 7 years ago on 21 July 2016. Two of the field seasons, in 2020 and 2021, were cancelled due to COVID. The last 4 meters of the ice core was drilled with a rock drill setup due to the presence of pebbles in the ice. The very last core was drilled 21 July 2023. Chief driller Steffen Bo Hansen from the Niels Bohr Institute, University of Copenhagen said: “The rock drill got stuck at the bottom and we feared we would lose the last core and the drill. Getting the drill loose was difficult because it was stuck in the wet mud at the bottom. We have successfully drilled through the ice stream and finding mud under the ice is amazing.”

Prof. Dr. Ilka Weikusat, glaciologist at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) coordinates the German EGRIP contribution and was herself involved in the drilling. She describes: “I am very excited about the whole ice core, but also about the water-saturated sediment mud cores, which are the starting point for further research: Why does the Northeast Greenland Ice Stream originate here of all places? The interaction of water and sediment as a lubricant on the bedrock seems to be confirmed. Further observations and considerations will now enable us to understand the hydrological system under the ice sheet. So we remain curious, especially about the overall dynamics of the system: stretching ice block and subsurface shear. And we remain excited about the sample material obtained and further indirect geophysical data to be able to provide more circumstantial evidence and proof of how such an ice highway works.”

Knowledge on how the Greenland ice streams move are key to understand how sea level rise will be in the future. The ice loss from the Greenland ice sheet is a major contributor to sea level rise and is expected to increase as the temperatures over Greenland continue to rise.  Half of the ice loss is from the ice streams surrounding Greenland and the behavior of the ice streams is not well known. The results from the EGRIP ice core drilled through the North East Greenland Ice Stream will thus advance the accuracy of predictions of sea level rise.

Leader of the project Dorthe Dahl-Jensen from University of Manitoba and the Niels Bohr Institute of Copenhagen said: “I am so excited about the success. I have followed the flow of the ice by measuring the shape of the borehole through the years with a borehole logger. The fact that the ice is sliding like a block on mud will change the models and improve the sea level predictions.  The measurements also show that the ice is indeed melting at the base.”

The ice core itself is a 120,000 year long climate record that is being analyzed in tens of laboratories around the World. The quality of the ice core is excellent, and will document the glacial climate, the warm and cold periods during our present interglacial the last 11.700 years and the man-made changes during the anthropogenic period. The ice cores contain extremely rich information on past environments, which can be extracted from the ice itself, from impurities in the ice and from bubbles trapped in the ice of ancient atmosphere along with its content of greenhouse gasses.

Background information

The international EGRIP project has participation from 12 nations.  These contributing nations are Denmark, US, Germany, Japan, Norway, Switzerland, China, Canada, France, South Korea, UK and Sweden. The logistics have been done by University of Copenhagen and US National Science Foundation. All nations have participated in field work and ice core drilling. 40% of the more than 600 field participants have been young scientists being trained at the international environment at EGRIP (31 %  senior scientists,  29% supporting staff). Samples from the ice cores have been analyzed in more than 30 laboratories and the first xx papers have been published. Information on the project, publications and field work can be found on the homepage eastgrip.org. The EGRIP ice core is stored in the Danish ice core repository together with