Mass balance

Mass balance is the difference between accumulation and ablation. Variations in glacier mass balance often give reliable indications of changes in climate. The mass balance is positive if the glacier gains more than it loses. Snow can accumulate during summer at high elevations and ablation sometimes wins over the accumulation of snow during winter at the lowest elevations close to the termini of the glaciers. Elsewhere on the glaciers, snow accumulates during winter and snow and ice are removed by ablation during summer.

 

Mass balance measurements in the spring. A core reaching the previous autumn surface, which is often darker due to windborne dust. Ice lenses formed by melting and refreezing are sometimes visible near the bottom of the annual layer. The  length of the core indicates the amount of winter accumulation (from September to May). Photo: Hrafnhildur Hannesdóttir.

Mass balance measurements in the spring. A core reaching the previous autumn surface, which is often darker due to windborne dust. Ice lenses formed by melting and refreezing are sometimes visible near the bottom of the annual layer. The  length of the core indicates the amount of winter accumulation (from September to May). Photo: Hrafnhildur Hannesdóttir.

Mass balance measurements in the spring. A core reaching the previous autumn surface, which is often darker due to windborne dust. Ice lenses formed by melting and refreezing are sometimes visible near the bottom of the annual layer. The  length of the core indicates the amount of winter accumulation (from September to May). Photos: Hrafnhildur Hannesdóttir, 2008.

 

Winter, summer and annual mass balance of Vatnajökull since the beginning of measurements in 1992. Source: Glaciology Group at the Institute of Earth Sciences, University of Iceland.

Winter, summer and annual mass balance of Vatnajökull since the beginning of measurements in 1992. Source: Glaciology Group at the Institute of Earth Sciences, University of Iceland, 2019.

 

Annual mass balance of Vatnajökull 2016–2017. Source: Glaciology Group at the Institute of Earth Sciences, University of Iceland, Pálsson (2017).

Annual mass balance of Vatnajökull 20162017. Source: Glaciology Group at the Institute of Earth Sciences, University of Iceland, Pálsson (2017).