evidence: The Southern Patagonia Icefield (SPI, Fig. 1) is a temperate ice mass (Warren and Sugden, Reference Warren and Sugden1993) that spans the territories of Southern Chile and Argentina, and constitutes most of the land ice stored in South America (Pfeffer and others, Reference Pfeffer2014). This region has become increasingly important due to its global sea level rise contribution (Rignot and others, Reference Rignot, Rivera and Casassa2003; Willis and others, Reference Willis, Melkonian, Pritchard and Rivera2012b; Gardner and others, Reference Gardner2013). Most of the ablation zones of the SPI glaciers are retreating with high thinning rates, resulting in lake/fjord expansions, the growth in the number of proglacial lakes, the increasing occurrence of glacial lake outburst floods, massive calving events and landslides in formerly ice-covered areas (Wilson and others, Reference Wilson, Carrión and Rivera2016, Reference Wilson2018; Harrison and others, Reference Harrison2018; Lenzano and others, Reference Lenzano2018). [...] At San Rafael Glacier (Northern Patagonia Icefield) modelling results show that basal sliding accounts for 98% of the observed surface ice velocity in the fast-flowing part of the glacier (Collao-Barrios and others, Reference Collao-Barrios2018). Following these results, we assume that on Jorge Montt Glacier the vertically averaged ice velocity $\bar {u}_{\rm i}$ equals the measured surface ice velocity v i (Pfeffer, Reference Pfeffer2007). The ice discharge Q i through a fluxgate is calculated by integrating ice velocity $\bar {u}_{\rm i}$ across a transverse profile: