Historical ablation rates and their drivers in Greenland – assessing the potential of the Wegener expedition for modern glaciological research

Alfred Wegener contributed extraordinarily to early days of scientific explorations in Greenland. Involved in three expeditions, we present unique historical data that is stored at Graz University, where Wegener filled his last academic position until his tragic death in Greenland in 1930. In this contribution we reevaluate data from his last expedition 1929-1931 acquired at the Qaamarujuup Glacier in West Greenland (71°09'N; 51°11'W). Sub-weekly ablation measurements along with air temperature, humidity, pressure, wind and short-wave radiation data exist for two full ablation seasons both near sea level and in 950 m a.s.l.. The 20^th Century reanalysis product of the nearest grid-point performs well reproducing air temperature variability. Coincidentally, this expedition was carried out during a very warm period that was in fact comparable to recent years. We compare vertical ablation gradients from the years 1929/1930 obtained at Qaamarujuup in West Greenland with recent observations from the closest PROMICE automated weather station and discuss differences in a centennial perspective. Furthermore, we present a time-series of glacier stages from the little ice age (LIA) maximum up to present and quantify area and volume changes since. The glacier margin was in close proximity (<50 m distance) to the ocean during the LIA maximum, 660 m and almost 3 km horizontal distance from the ocean in 1930 and in 2019, respectively. Such a drastic geometrical change manifests in differing drivers of the glacier boundary layer with the impact of the cooling ocean during summer decreasing with time as the glacier margin’s distance to the ocean increases. We discuss the potential in using historical glacio-meteorological measurements along with a detailed glacier history in order to extract geometrical feedbacks from the climate change signal.