Initial survey of blue ice areas for the recovery of old ice in the Sør Rondane mountains (Dronning Maud Land, East Antarctica)

<ns5:p> Blue ice areas have the potential to preserve old ice near the surface, offering valuable archives of past climate beyond the range of continuous deep ice cores. Notably, million-year-old ice has been recovered at shallow depths in the Allan Hills blue ice area, in the Transantarctic Mountains. However, similar sites in other regions of Antarctica remain unexplored. The FROID project aims to identify and sample such old ice near the Belgian Princess Elisabeth Station in Dronning Maud Land, East Antarctica. This report details the first of two field expeditions, conducted during the austral summer of 2024–2025, with the goal of identifying a suitable drilling site for a shallow ice core (up to 200 m) in the Nils Larsen blue ice area. During the field campaign, we collected datasets to assess ice age, thickness and flow velocity, to determine potential and suitability for coring very old ice: (1) 10 m ice cores for absolute dating ( <ns5:sup>81</ns5:sup> Kr and <ns5:sup>40</ns5:sup> Ar methods), gas measurement (amongst others, δO <ns5:sub>2</ns5:sub> /N <ns5:sub>2</ns5:sub> , total air content, CO <ns5:sub>2</ns5:sub> , CH <ns5:sub>4</ns5:sub> , N <ns5:sub>2</ns5:sub> O) and ice fabrics; (2) surface ice samples for water stable isotope analysis (δ <ns5:sup>1</ns5:sup> 8O and δD) to infer paleo-temperatures and spatial patterns in isotopic variation; (3) ground-penetrating radar (GPR) surveys of bed topography and ice thickness; (4) ApRES radar profiles for vertical velocity, internal structure, and ice fabric; (5) GNSS measurements for local ablation and surface motion; and (6) Uncrewed Aerial Vehicle (UAV) tests for future meteorite recovery applications. This report outlines the field preparation, methodologies used, and challenges encountered. The results will guide site selection for the follow-up drilling campaign and can serve as a practical guide for future blue ice fieldwork. </ns5:p>