In-situ tracer percolation experiments to constrain the influence of near-surface melting on Svalbard snow signatures

Abstract. The Arctic is at the forefront of global warming. More frequent and intense rain-on-snow events during winter are altering the annual snowpack with its environmental proxy records, so that Svalbard glaciers are not only rapidly losing mass but are endangered as climate archives. In this study, we aim to visualise and better constrain the influence of near-surface melt caused by small-scale rain-on-snow events on stable water isotope signatures in seasonal snow in the vicinity of Ny-Ålesund in Svalbard. To this end, we first introduce a simple in-situ melt tracer experiment approach and subsequently present new insights into structural imprint and stable water isotope alteration gained during field experiments near Ny-Ålesund in March 2023. We document diverse features resulting from meltwater infiltration, including unprecedented observations of internal layering within melt lenses, and discuss the importance of snow temperature and stratigraphy for percolation behaviour, ranging from preferential to matrix flow in the non-ripe snowpack. Comparisons of δ¹⁸O and δ²H signatures before and after each experiment further reveal that percolation-induced stable water isotope changes are localized, i.e. confined to melt structures, so that sub-annual stable water isotope information can be retrieved from unaffected profile parts where annual accumulation is sufficient.