Spatial variability of glacier mass and energy balance in West Greenland

Abstract:

The Greenland ice sheet has gained attention in recent years due to an increasingly negative mass balance, particularly since the 1990s. Less studied, however, is the Greenland mountain glaciers’ recent past, albeit their importance in terms of modern sea-level changes. There is a lack of understanding on to what extent observations on the ice sheet can be upscaled to approximate the mass change of the mountain glaciers. Strong horizontal climate gradients are known to exist but especially in higher altitudes they are based on poor data coverage. We make use of the Machguth et al. (2015) data base that comprises of point mass balance observations all around Greenland, which reveals that typical horizontal coast-to-ice sheet mass balance gradients amount to -10 mm/km at around 66°N and are strongest in south Greenland with -18 mm/km at 61°N with a more negative mass balance further inland. In the Godthåbsfjord area (64°N, 50°W) several valley AWS exist that allow to describe the complexity of low-elevation climate gradients, which show strongest temperature gradients very close to the shore, while precipitation gradients are stronger further inland. Using AWS data from PROMICE (www.promice.dk) and GEM (http://www.g-e-m.dk), we calculate high elevation coast-to-ice sheet climate gradients and compare them with the valley data. Most climate parameters show weaker gradients in high elevation compared to the valley sites. From detailed surface energy and mass balance calculations we conclude that the decisive factor for the significant mass balance gradients is winter accumulation, impacting the duration of the snow-free period. Finally, we discuss further steps necessary for upscaling to a Greenland scale.