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

Abstract:

The Kaskawulsh Glacier is an excellent indicator of regional glacier change: it represents ∼9% of glacier-ice volume in Yukon, and experienced rates of mass loss from 1977-2007 nearly identical to those calculated for the St. Elias Mountains as a whole. It is also an ideal target for understanding glacier response to a changing climate, being one of few large glaciers in the region not known to surge. New geodetic and geophysical data present a unique opportunity to investigate a decade of change over this glacier: here 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 within the ablation zone of the glacier, 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 cross-sectional areas derived from new ice-penetrating radar data. We find the glacier is still in the early stages of dynamic adjustment to its mass imbalance, with a committed terminus retreat of ∼23 km under the 2007-2018 climate and at least 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 large land-terminating glaciers.