Improving our Understanding of Melt-Affected Ice Cores Through In-Situ Percolation Tracer Experiments

Rising global temperatures and accelerated melting cause glaciers across the globe to shrink, thereby hampering our ability to reconstruct past climate from ice cores across the globe. In this context, melt-induced alterations of chemical signals in ice cores are an increasing issue not only for researchers working on mid- and low-latitude glaciers but in coastal Antarctica, Greenland, and other (sub-)polar sites, too. Aiming to contribute to a more comprehensive understanding of ice cores as environmental archives when affected by melt, Moser et al. (2023) have recently conducted an in-depth review of the existing literature regarding external drivers of melt events, physics of melt layer formation and behaviour during snow metamorphism, identification and quantification of melt, structural characteristics of melt features, effects of melting on records of chemical impurities, stable water isotopic signatures, and gas record, as well as applications of melt layers as environmental proxies. By briefly walking through formation, manifestation and potential interpretation of refrozen melt sections, we here provide an overview of those aspects of near-surface melting, which are important for ice-core record interpretation more widely. Against this backdrop of existing research and gaps of knowledge, we present the setup and first results of percolation tracer experiments conducted during a field campaign near Ny-Ålesund, Svalbard, in March-April 2023. Showing the alteration of snowpack structure and chemistry through liquid water in-situ, the experiments have provided new insights into (1) meltwater flow and refreezing processes in the vicinity of Ny-Ålesund, and (2) the informational value of stable water isotope records before and after rain-on-snow induced melt events. Finally, we compare these in-situ observations to high-resolution structural scans of melt features in ice cores to explore further conclusions, which help to improve our understanding of melt-affected ice cores. Moser, D. E., Thomas, E. R., Nehrbass-Ahles, C., Eichler, A., & Wolff, E. (2023). Melt-Affected Ice Cores for (Sub-)Polar Research in a Warming World. EGUsphere Preprint. https://doi.org/10.5194/egusphere-2023-1939