Mass balance and meteorological measurements

Regular mass balance monitoring of Vatnajökull has been carried out since 1992 in cooperation between the Institute of Earth Sciences of the University of Iceland and the National Power Company. The accumulation of snow is measured in the spring by drilling cores through the winter snowpack and the ablation of snow and ice by measuring changes in the height of stakes or the length of wires left in boreholes drilled into the glacier ice. The resulting mass balance data set is used in studies of glacier volume changes, to estimate melt­water contribution to glacial rivers (runoff), in mass balance modelling and to evaluate altitudinal and regional variations of mass balance in response to climatic variations. Mass balance maps have been derived, using the mass balance measurements and observed vertical mass balance gradient (that is the statistical relation between elevation and mass balance).

Automatic weather stations have been operated on the ice cap in summer since 1994. They measure temperature, relative humidity, wind speed and wind direction, as well as radiation components. The meteorological data are used to estimate the relationship between melting and weather components. The data are also used in mass balance modelling.

The influence of volcanic tephra and dust from the san­dur plains on the mass balance of the ice cap has been studied extensively. Deposition of small amounts of airborne dust on glaciers can cause enhanced melting due to the reduction of surface albedo. However, the thickness of the tephra or dust plays a decisive role. A thin layer increases the snow and ice melt but a layer exceeding ca. 10–15 mm in thickness causes insulation. The influence of volcanic ash is strong immediately following an eruption, but the tephra is rapidly covered by winter snow in the accumulation area and washed away in the ablation area.

The Breiðamerkurjökull outlet glacier retreats and thins due to negative surface mass balance in a warming climate but also due to calving into Jökulsárlón lagoon. Calving currently causes about 1/3 of the mass loss of Breiðamerkurjökull.

 

Mass balance measurement sites on Vatnajökull. Source: Glaciology Group, Institute of Earth Sciences, University of Iceland.

Mass balance measurement sites on Vatnajökull. Source: Glaciology Group, Institute of Earth Sciences, University of Iceland. 

 

Automatic weather station on Vatnajökull. Photo: Einar Ragnar Sigurðsson.

Automatic weather station on Vatnajökull. Photo: Einar Ragnar Sigurðsson.

 

Calving front of Breiðamerkurjökull. Photo: Þorvarður Árnason, 2018.

Calving front of Breiðamerkurjökull. Photo: Þorvarður Árnason, 2018.