Resolving Enthalpy Budget to Understand Surging (REBUS)

Kongsvegen (The King’s Highway) is a glacier in Svalbard which last surged in 1948, since when it has been melting in its lower reaches and building up snow in its upper parts. GPS measurements by the Norwegian Polar Institute have detected an acceleration from 6 m per year (2004-2013) to 12 m per year (2016-2017). Although ice motion is still slow, it is clear that the transition to a surge has begun, providing a rare opportunity to understand the earliest stages of a surge and the processes that underlie this enigmatic behaviour. The REBUS project aims to conduct detailed measurements on Kongsvegen and use the data to test a new theory of glacier surges. The theory is based on the enthalpy (internal energy) budget of the glacier. Stated simply: in the long term glaciers need to find a balance between rates of ice flow and enthalpy gains and losses at the bed. Ice flow creates frictional heating at the bed of the glacier, which increases its enthalpy content (heat and water). Because heat and water cause more rapid ice flow, they must be able to escape from the bed as fast as they are produced, or the glacier will accelerate. "Normal" glaciers are able to find the right balance, whereas surge-type glaciers must undergo cyclic swings in mass and energy content. To test enthalpy theory, the REBUS project has three objectives: (1) Measure ongoing and recent geometric and dynamic evolution of the glacier; (2) Quantify the enthalpy budget of the glacier; and (3) Model the key processes governing surge evolution. Field data will be collected in spring 2018, including: installing instruments within and beneath the ice to monitor heat and water content; and conducting ground-penetrating radar surveys of the glacier bed. Glacier velocities will be measured using satellite image analysis and high-precision GPS instruments. The observations will provide input for a state-of-the art computer model of glacier dynamics, which will be used to test detailed predictions of enthalpy theory.