The vertical structure of the troposphere and its connection to the surface mass balance of Flade Isblink in northeast Greenland

Abstract. Glaciers and ice caps (GIC) north of 79° N in Greenland contributed around 60 % to the total mass loss of all GIC in Greenland between 2018 and 2021, driven largely by surface melt in response to rising temperatures. Vertical temperature structures in the lower atmosphere modulate the surface energy exchanges and are an important factor in governing surface melt. Despite this importance, few in situ observations are available. We measured 130 vertical air temperature profiles up to 500 m above ground using uncrewed aerial vehicles (UAVs) over different surface types around Villum Research Station (VRS) in Northeast Greenland. VRS is 5 km west of Flade Isblink ice cap (FIIC), the largest peripheral ice mass in Greenland. We find a robust agreement between the UAV temperature profiles and the ones of the Copernicus Arctic Regional Reanalysis (CARRA) data set (mean absolute difference of 1 °C; r=0.59), which allows us to use CARRA for a detailed process study. Using daily CARRA data for June, July and August from 1991 to 2024, we find that surface properties significantly (p<0.01) control air temperature variability up to ∼100 m above ground. K-means clustering of vertical temperature gradients above 100 m above ground reveals that the profiles reflect distinct large-scale synoptic conditions. We assess the influence of the synoptic conditions on the surface mass balance (SMB) of FIIC using output from the Modèle Atmosphérique Régional (MAR). Overall, mass loss of ∼21 Gt occurred since 2015, driven by summer air temperatures under all synoptic conditions. The most extreme melt season with a SMB of −0.8 m water equivalent and an equilibrium line altitude estimated 467 m above average occurred in 2023, associated with frequent synoptic conditions favourable for melt.