Glaciological and geodetic mass balance of ten long-term glaciers in Norway

Abstract

Abstract. The glaciological and geodetic methods provide independent observations of glacier mass balance. The glaciological method measures the surface mass balance, on a seasonal or annual basis, whereas the geodetic method measures surface, internal and basal mass balances, over a period of years or decades. In this paper, we reanalyse the 10 glaciers with long-term mass balance series in Norway. The reanalysis includes (i) homogenisation of both glaciological and geodetic observation series, (ii) uncertainty assessment, (iii) estimates of generic differences including estimates of internal and basal melt, (iv) validation, and (v) partly calibration of mass balance series. This study comprises an extensive set of data (454 mass balance years, 34 geodetic surveys and large volumes of supporting data, such as metadata and field notes). In total, 21 periods of data were compared and the results show discrepancies between the glaciological and geodetic methods for some glaciers, which in part are attributed to internal and basal ablation and in part to inhomogeneity in the data processing. Deviations were smaller than 0.2 m w.e. a−1 for 12 out of 21 periods. Calibration was applied to seven out of 21 periods, as the deviations were larger than the uncertainty. The reanalysed glaciological series shows a more consistent signal of glacier change over the period of observations than previously reported: six glaciers had a significant mass loss (14–22 m w.e.) and four glaciers were nearly in balance. All glaciers have lost mass after year 2000. More research is needed on the sources of uncertainty, to reduce uncertainties and adjust the observation programmes accordingly. The study confirms the value of carrying out independent high-quality geodetic surveys to check and correct field observations.

Use of an ultra-long-range terrestrial laser scanner to monitor the mass balance of very small glaciers in the Swiss Alps

“…Resulting values for σ B direct presented here are similar to the one reported for Storglaciären (Jansson, 1999), but significantly smaller compared to the majority of all measured glaciers worldwide (e.g., Thibert et al, 2008;Beedle et al, 2014;Andreassen et al, 2015). This can be explained by the fact that the density of winter and summer point measurements is comparatively much more complete and substantially higher for our study glaciers than for most other glaciers (Supplementary Tab.…”

“…mass changes computed over pentadal to decadal time periods based on high-resolution source data (e.g. Andreassen et al, 2015;Magnússon et al, 2016).…”

The impact of pro‐glacial lakes on downstream sediment delivery in Norway

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Liquid water storage in snow and ice in 86 Eastern Alpine basins and its changes from 1970–97 to 1998–2006

“…Geodetic determination of storage change in glaciers based on DEM differencing may be better than ±150 mm (Abermann and others, 2010; Bollmann and others, 2011); conventional glacier mass balances may have errors of 100–200 mm (e.g. Andreassen and others, 2015). The contribution of these uncertainty values to overall uncertainty is distinctly reduced by the ratio between glacierized to total area.…”