WP4: Calving processes
UNIS (Benn), NPI (Kohler), UiO, UMB (Rolstad), (USi, IMAU)
Automatic camera overlooking Kronebreen (photo: M. Sund)
Close up of camera 2 overlooking Kronebreen (photo: M. Sund)
A new time-dependent model, which predicts changing ice front positions and calving fluxes for tidewater glaciers, will be tested and developed using data from Kronebreen. The model builds upon recent approaches23,24 by incorporating a physically-based calving criterion, whereby terminus position is determined from the depth of transverse crevasses calculated from the longitudinal velocity gradient25. Feedbacks between ice thickness, basal effective pressure, ice velocity, dynamic thinning, and calving flux are incorporated via the sliding relation. The proposed work on Kronebreen aims to: 1. obtain high resolution data on the glacier velocity field and its derivatives, 2. conduct force-balance analyses for different times of the year, to relate stretching and calving rates to forces driving and resisting glacier flow; 3. establish the spatial and temporal controls on individual calving events, including terminus stretching rates and
1) Velocity and calving data will be obtained from time-lapse stereo-photogrammetry, using digital camera pairs located on high vantage points above the glacier. Ortho-images will be produced with reference to surveyed tie-points near the glacier. This approach will yield time series of velocities and strain rates at up to hourly resolution, concurrently with records of calving events and changes in terminus position, representing a major improvement on currently available data sets. Additional velocity data will be obtained by remote sensing (WP 2). Data will be used in conjunction with basal topography in force balance analyses26,27, and meltwater fluxes modeled from energy balance data (1.2.2) will be used to analyse the role of possible external controls.