Glacier mass-balance and discharge modeling

• Main Author: Engelhardt, Markus
• Format: Dissertation
• Language: English

Glaciers are among the most frequently used natural phenomena to illustrate ongoing global warming. Retreating glacier tongues and the reduction of glacierized areas are visible all over the world. Changes in glacier volume affect both the river runoff regime downstream and sea level. In Norway, mountain glaciers and associated streamflow are of particular importance since the electricity sector relies on hydropower. The spatial and temporal distribution of glacier mass-balance and discharge measurements from glacierized catchments is therefore biased towards demands from hydropower utilization. This study investigates glacier mass balance and associated meltwater discharge together with their spatial and temporal variations. A mass-balance model has been adapted to the glacierized area in Norway using temperature and precipitation data from seNorge (http://www.senorge.no) and potential solar radiation as input. The data from seNorge are available for the whole country on a 1 km horizontal grid and on a daily time step from 1957 to present. The gridded data from seNorge are evaluated using winter mass balances at point locations on glaciers in different regions across the country. Results indicate that the seNorge data are suitable for mass-balance modeling, but further adjustment of the precipitation data should be performed. The modeled mass balances for the glacierized area of Norway yield a overview of spatial averaged glacier mass balance from 1961-2010. Seasonal mass balances show large year-to-year variability. Nevertheless, the winter and annual glacier mass balance show positive trends over 1961-2000 followed by a remarkable decrease in both summer and winter balances in the years 2000-2010 resulting in an average annual mass balance of close to -1 m w.e. (water equivalent) a-1 for the first decade of the 21st century. The mass balance sensitivities to temperature and precipitation variations are much larger for glaciers in maritime than for continental climate conditions. Despite the large extent of the Norwegian mainland from north to south, the mass balance sensitivities to temperature and precipitation changes show a stronger gradient from west to east. For the period 1961-2012, discharge is modeled for three catchments with a glacierization between 50-70 % situated along a west-east profile in southern Norway. The model simulations reveal an increase of the relative contribution from glacier melt to discharge from less than 10 % in the early