Glaciers are key indicators of climate change. While the mass balance of a glacier reflects annual weather directly, records of length change (also termed front-position change) can be used for climate change detection on a decadal-to-century time scales. When a glacier advances or retreats its surface area also changes. Here NVE’ records of surface mass balance and length change for glaciers in mainland Norway are shown. The data are retrieved directly from NVE’s database. For some of the glaciers area maps are also shown. Read more about the data series below the map.
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Some of the selected glaciers have long time series (more than 20 years) of mass balance or length observations and are selected for the “Norwegian Reference Hydrological Dataset for Climate Change Studies” (Fleig et al., 2013). Here data are shown for all glaciers with a mass balance or length change record in NVE’s database. The mass balance and length change measurements have been published annually or biannually since 1963 (e.g., Kjøllmoen et al., 2017). The data are also reported to the World Glacier Monitoring Service and stored in their databases.
NVE’s glacier surface mass balance series contain annual (net), winter and summer balances (Andreassen et al., 2005; Kjøllmoen et al., 2017). The annual balance is the sum of winter balance and summer balance. Area-averaged values for winter and summer balances are calculated by inter- and extrapolating point measurements of snow density, snow depths and ablation. The data presented here are official values from NVE. The series are categorized as ‘original’ (as published in ‘Glasiologiske undersøkelser i Norge/Glaciological investigations in Norway), ‘homogenized’ (for selected or all years) or ‘calibrated’ (periods are calibrated with geodetic observations). Five of the series (Engabreen, Nigardsbreen, Rembesdalskåka, Ålfotbreen and Hansebreen) have been calibrated for parts of the observation period (Andreassen et al., 2016). Furthermore, several of the short term series have been homogenized (Kjøllmoen, 2017). An area-weighted annual mass balance signal reflects a year’s weather directly, however, for longer time series changes in glacier area will also influence the annual balance. Thus, care should be taken when analyzing long time series as they may contain effects other than just climate change.
Glacier length change is derived from annual, repeated measurements of distance between the glacier terminus and fixed landmarks. It should be noted that in contrast to mass balance measurements, length change does not require annual measurements to have a continuous series. If one year’s data is absent, length change is derived from two years instead of one, maintaining the cumulative signal. Nonetheless, some of the length change series are discontinuous. This is shown by a red vertical line in the diagram.
Glacier area changes are calculated from detailed glacier maps, and from the NVE/CryoClim glacier area outline data. Data are displayed as tables and illustrations. It should be noted that there will be several uncertainties in the area change assessments since glacier areas are derived from different sources (Landsat, topographic maps or tabular data), often with different snow conditions. Each method has its specific uncertainties and area changes may partly be due to differences in methods, snow conditions or human interpretation rather than real glacier changes. (Andreassen et al. 2008).
Referanser og mer informasjon:
Andreassen, L.M., H. Elvehøy, B. Kjøllmoen, R.V. Engeset and N. Haakensen. 2005. Glacier mass balance and length variations in Norway. Annals of Glaciology, 42, 317–325.
Andreassen, L.M., F. Paul, A. Kääb and J.E. Hausberg. 2008. Landsat-derived glacier inventory for Jotunheimen, Norway, and deduced glacier changes since the 1930s. The Cryosphere, 2, 131–145. (pdf)
Andreassen, L.M., S.H. Winsvold, F. Paul and J.E. Hausberg. 2012. Inventory of Norwegian glaciers. NVE Rapport 38.(pdf)
Andreassen, L.M., H. Elvehøy, B. Kjøllmoen and R.V. Engeset. 2016. Reanalysis of long-term series of glaciological and geodetic mass balance for 10 Norwegian glaciers, The Cryosphere, 10, 535-552, doi:10.5194/tc-10-535-2016, 2016.(pdf)
Fleig, A.K. (ed.), L.M. Andreassen, E. Barfod, J. Haga, L.E.Haugen, H. Hisdal, K. Melvold and T. Saloranta. 2013. Norwegian hydrological reference dataset for climate change studies. NVE Rapport, 2. (pdf)
Kjøllmoen, B. 2017. Homogenisering av korte massebalanseserier i Norge. NVE Rapport 33- 201, 130 p. (pdf)
Kjøllmoen, B. (Ed.), L. M. Andreassen, H. Elvehøy, M. Jackson and K. Melvold. 2017:.Glaciological investigations in Norway in 2016. NVE Report 76 2017, 95 p. +app.(pdf)
Paul, F. and L.M. Andreassen. 2009. A new glacier inventory for the Svartisen region (Norway) from Landsat ETM+ data: Challenges and change assessment. Journal of Glaciology, 55 (192), 607–618.
Paul, F., L.M. Andreassen and S.H. Winsvold. 2011. A new glacier inventory for the Jostedalsbreen region, Norway, from Landsat TM scenes of 2006 and changes since 1966. Annals of Glaciology, 52 (59), 153–162.
Winsvold, S.H., L.M. Andreassen and C. Kienholz. 2014. Glacier area and length changes in Norway from repeat inventories. The Cryosphere, 8, 1885-1903.(pdf)