Modelling the mass balance of northwest Spitsbergen glaciers and responses to climate change

An energy-balance model is used to calculate mass balance and equilibrium-line altitudes (ELAs) on two northwest Spitsbergen glaciers, Austre Brøggerbreen and Midre Lovénbreen, whose mass balances are at present negative, and for which greater than 20 year records of mass-balance data are available. The model takes meteorological data, ice-mass area distribution with altitude, and solar radiation as inputs. Modelling uses mean daily meteorological data from a nearby weather station, adjusted for altitude. Average net balances modelled for 1980–89 using models tuned to the decade’s average were –0.44 and –0.47 m w.e. for Lovénbreen and Brøggerbreen, respectively, compared with the measured averages of –0.27 and –0.36 m. Sensitivity tests on glacier response to greenhouse warming predict a net balance change of –0.61 m year–1 per °C temperature rise relative to today, and a rise in ELA of 90 m °C–1. Modelling of Little lee Age conditions in Spitsbergen suggests that a 0.6°C cooling or a precipitation increase of 23% would yield zero net mass balance for Lovénbreen and that further cooling would increase net balance by 0.30 m year–1 °C–1. Set in the context of similar modelling of southern Norwegian, Alpine and Greenland ice masses, these results support the suggestion that glaciers with a maritime influence (i.e. higher accumulation) are most sensitive to climate change, implying a gradient towards decreasing sensitivity as accumulation decreases eastward and with altitude in Svalbard.