The hydrological impact of rapid ice ablation in a small highly glaciated catchment, Virkísjökull, SE Iceland

Widespread glacial retreat in Iceland will lead to changes in the hydrology of proglacial rivers. An understanding of the connection between glaciers and rivers is necessary in order to predict and manage the anticipated changes. This paper presents a detailed ice ablation study from the Virkísjökull catchment in SE Iceland. This paper provides a better understanding of the connection between enhanced ice ablation, glacier hypsometry and proglacial river run-off during a rapid retreat phase. Degree-day modelling, river discharge monitoring and glacier hypsometric analysis from the 2013 ablation season was used. Results indicate that a 1°C warming will increase ice surface lowering by 8.5 mm d–1 in the lowest 200 m, which translates as 37% more melt available for river flow. Individual glacier hypsometry is responsible for a high sensitivity to fluctuations in the equilibrium-line altitude, with an increase of 100 m resulting in an increase in total meltwater input into the catchment of 13.4% currently levels between May and September. Virkísjökull is at a critical stage where the greatest increase in meltwater input that will be observed during this deglaciation cycle could occur within the next few years due to an increase in the altitude of the late summer snowline.