Two main types of freshwater enter the ocean at the termini of tidewater glaciers: submarine melt from ice that melts directly into the ocean, and subglacial discharge from surface melt or precipitation that drains to the bed of the glacier and then into the ocean. These freshwater sources form plumes that rise along the submarine terminus, driving mixing between glacial freshwater and seawater. The dynamics of these plumes affect both submarine melt rates and fjord circulation (e.g., Carroll et al., 2015;Jenkins, 2011). Subglacial discharge, in particular, plays a dual role in forcing both the ocean and glacier: it is often the largest source of freshwater into fjords, driving a strong buoyancy-driven circulation, and also modulates submarine melt rates by altering the turbulent transfers at the ice-ocean boundary (

Frontal ablation, the combination of submarine melting and iceberg calving, changes the geometry of a glacier's terminus, influencing glacier dynamics, the fate of upwelling plumes and the distribution of submarine meltwater input into the ocean. Directly observing frontal ablation and terminus morphology below the waterline is difficult, however, limiting our understanding of these coupled ice–ocean processes. To investigate the evolution of a tidewater glacier's submarine terminus, we combine 3-D multibeam point clouds of the subsurface ice face at LeConte Glacier, Alaska, with concurrent observations of environmental conditions during three field campaigns between 2016 and 2018. We observe terminus morphology that was predominately overcut (52% in August 2016, 63% in May 2017 and 74% in September 2018), accompanied by high multibeam sonar-derived melt rates (4.84 m d−1 in 2016, 1.13 m d−1 in 2017 and 1.85 m d−1 in 2018). We find that periods of high subglacial discharge lead to localized undercut discharge outlets, but adjacent to these outlets the terminus maintains significantly overcut geometry, with an ice ramp that protrudes 75 m into the fjord in 2017 and 125 m in 2018. Our data challenge the assumption that tidewater glacier termini are largely undercut during periods of high submarine melting.