Fig. 3. Temporal evolution of hydrographic conditions, meltwater content and basal melt rate.

a, Daily averaged time series of conservative temperature (Θ; red) and absolute salinity (S_A; blue) from the ocean mooring deployed 1.5 m beneath the ice base. b, Glacial meltwater (grey) and subglacial runoff (blue) derived from observations of Θ and S_A. c, Observed ApRES basal melt rate (green, purple, yellow and orange lines) low-pass-filtered with a 15-day cutoff plotted against the basal melt rate estimated from the three-equation melt-rate model (grey line; see Methods). The line colours for the ApRES basal melt-rate time series in c match their locations in Fig. 1. d, Θ–S_A diagram with σ₀ contours for the time series data in a coloured as a function of time. The blue and red dot-dashed lines are meltwater mixing lines that fit the observed data for January 2020 (blue) and August 2020 (red). The purple dot-dashed line is a mixing line between the grounding-zone Θ and S_A values in August 2020 and fresh subglacial runoff. The solid black line indicates the ambient mCDW–WW thermocline from ship-based CTD data (Fig. 2c), whereas the red-shaded box indicates the range of Θ and S_A values of the mCDW endmember. The grey dots show the CTD data from the borehole. e, Velocity vectors from the sub-ice current meter coloured as a function of time. Radial contours indicate flow speed in cm s⁻¹.