Dynamics of ionic species in Svalbard annual snow: the effects of rain event and melting

Abstract. The Arctic and middle latitude (such as the Alps) ice core archives, except for the Greenland summit, are strongly influenced by melting processes, able to modify the original chemical signal of the annual snowfall. In the last decades, the increase of the average Arctic temperature has caused and enhanced surface snow melting in the higher ice cap, especially in the Svalbard Archipelago. The increase of the frequency and altitude of winter “rain on snow” events as well as the increase of the length of the melting season has a direct impact on the chemical composition of the seasonal and permanent snow layers due to different migration processes of water-soluble compounds, such as ionic species. The re-allocation along the snowpack of ionic species could significantly modify the original chemical signal present in the annual snow, making comprehensive interpretation of climate records difficult. The chemical composition of the first 100 cm of the seasonal snow at Austre Brøggerbreen Glacier (Spitsbergen, Svalbard Islands, Norway) was monitored daily from the 27th of March until to the 31st of May 2015. The experiment period covers almost the entire Arctic spring until the melting season. During the experiment, a rain event occurred on the 16th to 17th of April while from the 15th of May the snowpack reached an isothermal profile. The presented dataset is unique and helps to better understand the behaviour of cations (K⁺, Ca²⁺, Na⁺, Mg²⁺), anions (Br⁻, I⁻, SO₄²⁻, NO₃⁻, Cl⁻, MSA) and two carboxylic acids (C₂-glycolic and C₅-glutaric acids) in the snowpack during this melting period. The results obtained from the experiment give us an overview of how the chemicals are remobilized in the snowpack during a rain event or due to the melting at the end of the spring season. The aim of this paper is to give a picture of the evolution of the seasonal snow strata with the aim to better understand the processes that can influence the chemical distribution in the annual snow. The results of the present work are unique and helpful for future analyses and interpretation of ice core paleoclimatic archives.