Fig. 3: Ocean conditions influence ice base morphology, which varies with distance from the GL.
From: Heterogeneous melting near the Thwaites Glacier grounding line
The Icefin vehicle track is shaded by relative along-track distance from downstream (white) to upstream (black). Light-blue data denote regions with cooling and freshening in terraces and dark blue denotes the coldest/freshest data observed. a, Conditions in the near-GL water cavity show the influence of melting (freshening) close to the GL along T2 (left). Coloured stars denote close passes to the ice that also have distinct signatures of mixing and melting. Vertical profiles of thermal driving (Θ − Θf), absolute salinity (SA) and dissolved oxygen (DO) binned with distance from the ice base show complex signatures that vary with location (Extended Data Fig. 3), suggesting the influence of both melting and SGW outflow (centre). Imagery near the GL (red box) shows ridged ice topography and sediment-laden clear basal ice at the GL (yellow star) (right). Scale bar, approximately 0.5 m. b, Ocean conditions in a large terrace formed in the ice base imply melting near the sidewalls (red boxes, 800 m from the GL along T2) (left). Warm, salty water (black, grey) is found along the sidewalls, whereas much fresher and more oxygenated water with low thermal driving (cold relative to in situ freezing) collects in the terrace roof (centre). Imagery of terrace sidewalls across the TEIS uniformly show scalloped surfaces reflecting turbulent melting (Extended Data Fig. 8 and Supplementary Video 1) (right). Scale bar, approximately 0.5 m. c, As in b but for a small terrace at 2,400 m downstream along T1 that contains cold, fresh and oxygen-rich water along its roof. Here the water becomes supercooled, with ice crystals forming laterally (right) across the heavily stratified interface (red box) between this 0.1 m upper boundary layer and the warm, saline and more oxygen-poor lower ocean waters. Scale bar, approximately 0.1 m.
