At the AWI ice laboratories, part of an ice core from the North Greenland Ice Stream (NEGIS) is currently being tested. The core was collected during “EastGRIP”, a joint project involving several international partners. Working together, they drilled to a depth of 2,668 metres, allowing them to penetrate the entire ice stream and reach the rocky substrate below. The analysis of the ice core is to yield new insights into the behaviour of ice streams and improve our grasp of how they could contribute to future sea-level rise. Another goal is to record past climatic conditions beneath the northeast section of the Greenland Ice Sheet. Numerous laboratories around the globe plan to analyse the data.
Due to a two-year forced delay in connection with the COVID-19 pandemic, the drilling took nearly six years to complete. The core segments harvested were stored in Copenhagen and subsequently transferred to a depot in Bremerhaven’s Fischereihafen district in refrigerated containers.
At the ice laboratories in Bremerhaven, the core is now being processed step by step. In terms of size and resources, the labs are unparalleled in Europe, offering a range of saws and instruments that can be used simultaneously. Two packing tables, a line scanner and an ECM (Electrical Conductivity Measurement) tester are available. These are the same tools that will be used to assess the EastGRIP ice core. For example, the line scanner can help visualise the ice stratigraphy. Moreover, 8 – 10 people can work simultaneously at the labs, which also feature an extreme-cold room (-30°C), where the ice core segments can be temporarily stored before being transported back to the ice depot in Fischereihafen.
At the moment, the core segment from ca. 2,121m to ca. 2,657m below the surface – collected during the field seasons in 2022 and 2023 – is being processed; the segment to a depth of 2,121m is already done. As the last one before reaching the bedrock, the remaining section, starting at 2,657m below the surface, is to undergo special processing and is currently being stored in Copenhagen.
In the course of processing, the ice core is methodically dissected, and initial tests are conducted. These include measuring its electrical conductivity and mapping its stratigraphy. These methods are used to identify characteristics like veins of dust from the last glacial period, and to determine the ice’s age. The youngest ice, which is currently in focus, is an estimated 50,000 years old, whereas the oldest ice is most likely more than 120,000 years old. Consequently, the ice is surprisingly much older than indicated by radar data gathered prior to the drilling. It stems in part from the interglacial period (referred to as the Eemian period) before the last glacial. These age estimates are based on measurements of the core’s electrical conductivity and comparisons with that of other Greenlandic ice cores that have already been dated.
Testing on particles like grains of sand or minuscule stones is to yield further valuable information. When were these particles last exposed to sunlight? This question can be answered with the help of the exposure dating method. And since this type of analysis can’t be conducted in Bremerhaven, those samples containing such particles will initially be stored separately in Copenhagen – safely packed in black sheathing, to ensure they aren’t exposed to light before testing.
In order to supplement the findings already gleaned, the AWI ice laboratories are currently running water isotope tests, which will allow more precise statements to be made on the ice’s age.