Study of local accumulation patterns from a snow trench at Dome C

The center of Antarctica contains some of the oldest ice available on earth for paleo-climate reconstructions. This is due to very slow ice-flow and low accumulation. Yet, low accumulation comes with the drawback that annual snow layers are thin and subject to erosion and re-deposition by wind, inducing locally mixing and sometimes missing snow layers, leading to a highly variable time vs depth gradient at sub-decadal timescales. This greatly limits the interpretation of the climatic record in ice-cores at high temporal resolution. An important challenge thus consists in describing and quantifying these local accumulation patterns on the East Antarctic plateau. In our study, we combine observations of accumulation rate (stake farm and laser scanner), with chemical and isotopic measurements of a 50-m long snow trench to address the problem of accumulation patterns at Dome C. We suggest that high resolution alignment of the chemistry data, typically used at longer timescales with volcanic eruption alignment in deep ice-cores, is a good method for inter-annual dating of the trench profiles and reconstruction of accumulation time-series up to a 2 year resolution. We find typical annually-varying roughness as well as more persistent patterns with timescales of years, highlighting the complex dynamics of the snow accumulation in central Antarctica. We then use this dataset to explore post-deposition noise in the isotopic record (δ18O and δD) and its local spatial variability.