Fig. 2. Hydrography and meltwater content beneath TEIS.

a,b, Vertical profiles of conservative temperature (Θ; red) and absolute salinity (S_A; blue) (a) and glacial meltwater content (grey) (b) collected over 4 days (9 to 12 January 2020) in the grounding-zone region of Thwaites Glacier (yellow star in Fig. 1). The ice base is indicated by the shaded grey box and the seabed is indicated by the slash-backed line. c, Θ–S_A diagram with σ₀ (density) contours for the grounding-zone CTD and Icefin data (large dots coloured by depth) and the ship-based CTD data from the International Thwaites Glacier Collaboration TARSAN project (small dots coloured by location: orange for Thwaites Trough, purple for Pine Island Bay and green for upstream that match the colours used to indicate their location in Fig. 1). The solid black line indicates the ambient mCDW–WW thermocline. The dot-dashed orange line indicates the meltwater mixing line that characterizes the grounding-zone data. The large black dot indicates where this meltwater mixing line intersects the ambient mCDW–WW thermocline. The thick orange dashes on the meltwater mixing line indicate 5 ml l⁻¹ intervals in glacial meltwater content, starting at 0 ml l⁻¹ at the large black dot. The dashed black line indicates the in situ freezing temperature as a function of salinity at the grounding line. The red and blue boxes with black outline indicate the range of Θ and S_A values of the mCDW and WW endmembers. The inset axes in c show the Θ–S_A relationship coloured by depth (note the different colour scale) for the CTD data from the well-mixed benthic boundary layer (purple box in the main plot). The dashed orange line indicates the slightly warmer meltwater mixing line that characterizes the data from this region of the water column.