Abstract ID: 28.7275 | Accepted as Talk | Talk | 2025-02-28 11:00 - 11:15 | Ágnes‐Heller‐Haus/Small Lecture Room

Due to glacier retreat and the collapse of lateral moraines, more and more glaciers are covered by debris in the ablation area, affecting the physics governing ice melt. Thick debris layer modulates and reduces the heat flux from the external environment to the ice. Traditionally, the only mechanism for heat transfer considered through supraglacial debris is conduction. Nevertheless, air and water can flow and through the debris, providing an extra source of heat transfer, i.e. convection. Moreover, change of state of interstitial water can represent a considerable source of latent heat. Here, thanks to the measurements campaign on Belvedere Glacier, on the East Massif of Monte Rosa, Italy, where we installed a climate station and several thermistors, we show evidence of these non-conductive processes in the debris layer. Classic second order heat equation proved insufficient to describe temperature variation through the debris. Hysteresis cycles at daily scale were detected, pointing to the presence of extra heat fluxes not explained considering only conduction mechanism. Particularly, during the late afternoon, non-conductive heat fluxes are directed from the terrain to the air, determining an extra source of cooling, while during the morning the heat is transferred to the debris. Incorporating a first order term provides significant improvement in explaining the link between temporal and spatial variation of temperature. Determination coefficient R2 passes from 0.88 of the single linear regression to 0.96 of the bi-linear regression considering both second order and first order term. The first order term is unlikely to be related to change in thermal conductivity, which keeps relatively constant with the depth, but it is likely due to convection and latent heat. Since in the considered period, precipitation is almost neglectable, and capillarity from the ice melting water is hindered by the thick layer of debris (c.a. 1.7 m), we assume that convection is a most relevant heat transfer mechanism in the study area. We recommend further studies to examine this phenomenon, possibly measuring humidity in the ground to provide a more precise assessment of latent and convective heat fluxes.