Glacier mass balance of Norway 1961–2010 calculated by a temperature-index model

Abstract

Glacier mass balance in Norway is only observed over a small portion (15%) of the glacierized surface and only for short time periods (10 years) for most sites. To provide a comprehensive overview of the temporal mass-balance evolution, we modeled surface mass balance for the glacierized area of mainland Norway from 1961 to 2010. The model is forced by operationally gridded daily temperature and precipitation fields which are available at 1 km horizontal resolution from 1957 until the present. The applied mass-balance model accounts for melting of snow and ice by using a distributed temperature-index approach. The precipitation input is corrected to obtain agreement between modeled and observed winter mass balance, and a melt factor and two radiation coefficients are optimized to the corresponding summer balance. The model results show positive trends of winter balance between 1961 and 2000 followed by a remarkable decrease in both summer and winter balances which resulted in an average annual balance of –0.86 0.15 m w.e. a–1 between 2000 and 2010 after four decades of zero to slightly positive annual mass balances.