Strong contrast in mass and energy balance between a coastal mountain glacier and the Greenland ice sheet

We show a strong difference in surface mass and energy balance of a mountain glacier and two sites on the ice sheet at 64°N in West Greenland using stake and automated weather station observations. Net surface mass balance is on average 2.2 m w.e. less negative at the coast compared with the ice sheet in the same elevation. We find a larger energy turnover at the ice sheet margin on Qamanarssup Sermia than measured on the coastal mountain glacier Qassigiannguit with both energy input and output being of larger absolute value. More cloudiness and a thicker snow cover at the relatively humid coastal glacier result in smaller gains in net-shortwave radiation and smaller losses in net-longwave radiation and a less negative mass balance. Lower wind speeds at the coastal glacier result in weaker turbulent heat exchange between atmosphere and ice surface. On annual average, 17 W m−2 more energy is available for melt at the ice-sheet margin compared with the coastal glacier in the same elevation

CHALLENGES OF QUANTIFYING MELTWATER RETENTION IN SNOW AND FIRN: AN EXPERT ELICITATION

Thirty-four experts took part in a survey of the most important and challenging topics in the field of meltwater retention in snow and firn, to reveal those topics that present the largest potential for scientific advancement. The most important and challenging topic to the expert panel is spatial heterogeneity of percolation, both in measurement and model studies. Studying percolation blocking by ice layering, particularly in modeling, also provides large potential for science advancement, as well as hydraulic conductivity and capillary forces in snow/firn. Model studies can benefit from improved initialization, and improved calculation of accumulation and liquid water at the surface. Firn coring should be performed more often, though we argue that also data that are relatively simple to collect, but of great importance to retention such as surface accumulation, density and temperature, are too sparse due to the high logistical expenses involved in field campaigns. Generally speaking, retention changes are expected to be of importance to the surface mass balance and thus ice loss in coming decades, more so for Greenland than Antarctica or ice masses elsewhere