Scientific history, sampling approach, and physical characterization of the Camp Century sub-glacial sediment core, a rare archive from beneath the Greenland Ice Sheet

• Main Authors: Bierman, Paul R., Christ, Andrew J., Collins, Catherine M., Mastro, Halley M., Souza, Juliana, Blard, Pierre-Henri, Brachfeld, Stefanie, Courville, Zoe R., Rittenour, Tammy M., Thomas, Elizabeth K., Tison, Jean-Louis, Fripiat, Francois
• Format: Text
• Language: English
• Published: 2024
• Subjects: Greenland; ice core; Ice Sheet
• Online Access: https://doi.org/10.5194/egusphere-2023-2922; https://egusphere.copernicus.org/preprints/2024/egusphere-2023-2922/

Basal materials in ice cores hold information about paleoclimate conditions, glacial processes, and the timing of past ice-free intervals, all of which aid understanding of ice sheet stability and its contribution to sea level rise in a warming climate. Only a few cores have been drilled through ice sheets into the underlying sediment and bedrock, producing limited material for analysis. The last of three Camp Century ice cores, which the U.S. Army collected in northwestern Greenland from 1963–1966 CE, recovered about 3.5 m of subglacial material, including ice and sediment. Here, we document the scientific history of the Camp Century subglacial material. We present our recent core-cutting, sub-sampling, and processing methodology and results for this unique archive. In 1972 CE, curators at the Buffalo, New York, Ice Core Laboratory cut the original core sections into 32 segments that were each about 10 cm long. Since then, two segments were lost and are unaccounted for, two were thawed, and two were cut as pilot samples in 2019 CE. Except for the two thawed segments, the rest of the extant core has remained frozen since collection. In 2021 CE, we documented, described, and then cut each of the remaining frozen archived segments ( n =26 ). We saved an archival half and cut the working half into eight oriented sub-samples under controlled temperature and light conditions for physical, geochemical, isotopic, sedimentological, magnetic, and biological analyses. Our approach was designed to maximize sample usage for multiproxy analysis, minimize contamination, and preserve archive material for future analyses of this legacy subglacial material. Grain size, bulk density, sedimentary features, magnetic susceptibility, and ice content, as well as pore ice pH and conductivity, suggest that the basal sediment contains five stratigraphic units. We interpret these stratigraphic units as representing different depositional environments in subglacial or ice-free conditions: from bottom to top, a diamicton with subhorizontal ...