Mapping Glacier Dynamics: A Flux-Gate Approach to Analysing Ice Discharge Variability and Sea Level Contributions in the Patagonian Icefields

This study used a flux-gate methodology coupled with ice thickness and ice velocity grids equivalent to 2004 and 2017 to ascertain ice discharge (Gt yr-1) and associated sea level equivalents (mm yr-1) through 124 outlet glaciers spanning the different termini environments of the Patagonian Icefields. In addition, glaciers that experienced a terminus environment transition (i.e., from land-terminating to lake-terminating or vice versa) were identified and any associated changes in ice discharge were quantified. Overall, total ice discharge equalled 24.59 Gt yr-1 (0.068 mm yr-1) in 2004 (Northern Patagonian Icefield = 7.07 Gt yr-1 or 0.019 mm yr-1, Southern Patagonian Icefield = 17.52 Gt yr-1 or 0.049 mm yr-1) and 23.94 ± 7.18 Gt yr-1 (0.066 mm yr-1) in 2017 (Northern Patagonian Icefield = 5.02 ± 1.57 Gt yr-1 or 0.014 mm yr-1,
Southern Patagonian Icefield = 18.92 ± 5.98 Gt yr-1 or 0.052 mm yr-1). In 2004 most of the ice was discharged through marine-terminating environments in the Western regions of the icefields. But, in 2017 there was a shift towards equilibrium whereby lake-terminating environments in the eastern regions matched the ice discharge of marine-terminating environments. This is attributed to the expansion of lake-terminating environments and an apparent acceleration of surface velocity. Although these trends do exist there were heterogeneous changes in ice discharge for all termini environments resulting from a complex array of dynamics at the calving front. A strong agreement was found between the ice discharge estimates in this study and geodetic mass loss estimates found in the literature, reinforcing the current knowledge around mass loss on the Patagonian Icefields. Future work should focus on the accuracy of ice thickness and ice velocity grids at the margins of icefields and using accurate frontal ablation estimates to constrain future sea level rise projections.