Centennial Changes in Microclimate and Surface Mass Balance: A West Greenland Case Study

The local microclimate is both a key driver and in turn impacted by glacier wastage. Such feedbacks become particularly relevant in rapidly changing regions such as for West Greenland, where e.g. Qaamarujup Sermia has retreated by approximately 2 km between 1930/31 and 2022. This is the site where Alfred Wegener’s last expedition took place and where its members conducted pioneering glaciological and meteorological studies . Starting in 2022, we re-established a spatially distributed monitoring network extending from the coastline to the upper glacier, including automated weather stations, distributed air-temperature and humidity sensors, and surface mass-balance stakes. These observations allow us to investigate how a significant increase in the extent of ice-free valley surfaces caused by glacier retreat influences altitudinal temperature profiles and, ultimately, glacier melt.
Cluster analyses of temperature gradients reveal that the often-assumed environmental lapse rate of −6.5 K per kilometer only applies under certain conditions. In several cases, lapse rates differ markedly between the ice-free valley and the air above the glacier and show complex patterns. We investigate how these patterns are linked to synoptic forcing and cloud conditions, which control the depth and persistence of temperature inversions. 
To quantify the implications of these microclimatic structures for glacier melt, we combine the atmospheric observations with high-resolution melt measurements from automated and conventional mass-balance stakes. We find that in recent years, higher melt rates occur under the same air temperature departure as they did in the 1930s.  Sparse snow observations indicate that snow accumulation in 1930/31, with a maximum snow height of approximately 2 m, was higher than in the years since 2022, but remains within the range of extreme snow amounts as for instance represented in the CARRA reanalysis period (1991-2024).
Together, our results demonstrate that ongoing glacier retreat at Qaamarujup Sermia not only responds to atmospheric forcing but can actively reshape the local microclimate, leading to increasingly effective melt processes. These feedbacks are critical for understanding future mass-balance evolution of glaciers in a changing climate.