| Summary: | This dataset contains resampled density data of 48 shallow firn cores collected in the percolation zone in southwest Greenland between 2012 and 2019. The original cores were presented in Machguth et al. (2016), MacFerrin et al. (2019), Vandecrux et al. (2019) and Rennermalm et al. (2021a), and can be accessed through the Arctic Data Center: http://doi.org/10.18739/A2125Q994 (Koenig and Montgomery, 2020) and http://doi.org/10.18739/A2Q52FD98 (Rennermalm et al., 2021b). In the original datasets, density was calculated as averages for core segments that could contain a mixture of snow, firn and ice. In this dataset, first presented in Xiao et al. (2022), a resampling method was applied to estimate density separately for each snow, firn and ice layers within the core segments. During the field drilling process, each firn core coming out of the drill barrel either naturally broke or was manually cut into multiple segments. For each segment an average density was measured in the field. Many core segments contain both firn/snow layer(s) as well as ice layer(s) which have distinctly different densities. Yet the measured segment-averaged densities cannot capture these spatial density variations within segments. To acquire more precise density profiles, we resampled the densities of all mixed ice-firn and ice-snow segments in these 48 cores so that all ice, firn and snow layers within a segment are assigned a distinct ice, firn and snow density, respectively. At the same time, the resampling processes aimed to preserve the original segment-averaged density. Quality control was performed for the resampled density data to replace unrealistic values. More details are provided in the method section below as well as in Xiao et al. (2022). The dataset includes the following files Core_meta_data.csv : File with metadata about each core, including location, site name, retrieval date, investigators, and other information. Explanation_of_core_variables.csv : File with explanation of the variables reported in the resampled density files. Resampled density files: For each core one file is included: a file including top and bottom depth, length, measured and resampled density, and other information of each core layer, with the following file naming convention [Site]_[YEAR]_[Core number]. Text in brackets are variables. References: Koenig, L., and Montgomery, L. Data from: Surface Mass Balance and Snow Depth on Sea Ice Working Group (SUMup) snow density subdataset, Greenland and Antarctica, 1950–2018. Arctic Data Center. (2020) http://doi.org/10.18739/A2125Q994 MacFerrin, M., Machguth, H., van As, D., Charalampidis, C., Stevens, C. M., Heilig, A., et al. (2019) Rapid expansion of Greenland’s low-permeability ice slabs. Nature 573, 403–407. doi: 10.1038/s41586-019-1550-3 Machguth, H., MacFerrin, M., van As, D., Box, J. E., Charalampidis, C., Colgan, W., et al. (2016) Greenland meltwater storage in firn limited by near-surface ice formation. Nat. Clim. Change 6, 390–393. doi: 10.1038/nclimate2899 Rennermalm, Å. K., Hock, R., Covi, F., Xiao, J., Corti, G., Kingslake, J., et al. (2021a) Shallow firn cores 1989–2019 in southwest Greenland's percolation zone reveal decreasing density and ice layer thickness after 2012. J. Glaciol., 1–12. doi: 10.1017/jog.2021.102 Rennermalm, Å. K., Hock, R., Covi, F., Xiao, J., Corti, G., Leidman, S. Z., et al. Data from: Density and ice layer stratigraphy in 24 shallow firn cores from Southwest Greenland, 2017–2019. Arctic Data Center. (2021b) http://doi.org/10.18739/A2Q52FD98 Vandecrux, B., MacFerrin, M., Machguth, H., Colgan, W. T., van As, D., Heilig, A., et al. (2019) Firn data compilation reveals widespread decrease of firn air content in western Greenland. Cryosphere 13, 845–859. doi: 10.5194/tc-13-845-2019 Xiao, J., Rennermalm, Å. K., Covi, F., Hock, R., Leidman, S. Z., Miège, C., et al. (2022) Local-scale spatial variability in firn properties in Southwest Greenland. Front. Earth Sci. 10:938246. doi: 10.3389/feart.2022.938246
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