An imbalancing act: the dynamic response of the Kaskawulsh Glacier to a changing mass budget

The Kaskawulsh Glacier is an iconic outlet draining the icefields of the St. Elias Mountains in Yukon, Canada. We determine and attempt to interpret its catchment-wide mass budget since 2007. Using SPOT5/6/7 data we estimate a 2007--2018 geodetic balance of -0.46 ± 0.17 m w. e.a-1. By comparing computed balance fluxes with observed ice fluxes at nine flux gates we examine the discrepancy between the climatic mass balance and internal mass redistribution by glacier flow. Balance fluxes are computed using a fully distributed mass-balance model driven by downscaled and bias-corrected climate-reanalysis data. Observed fluxes are calculated using NASA ITS_LIVE surface velocities and glacier crosssectional areas derived from ice-penetrating radar data. We find the glacier is still in the early stages of dynamic adjustment to its mass imbalance. We estimate a committed terminus retreat of ∼23 km under the 2007-2018 climate and a lower bound of 46 km3 of committed ice loss, equivalent to ∼15% of the total glacier volume. By combining our observations and model output using the continuity equation, we highlight challenges and opportunities in exploring the mass budget of Cambridge University Press Journal of Glaciology