New insights into Hydrology and Lake Dynamics Upstream of Thwaites Glacier

Understanding Antarctic subglacial hydrology is crucial for assessing ice sheet dynamics and their contributions to global sea-level rise. Subglacial water modulates basal friction, influencing ice flow and glacier stability, as shown in studies of Thwaites Glacier and other West Antarctic systems. Here, we present new insights into subglacial hydrology derived from geophysical observations. By integrating radar-derived bed reflectivity with subglacial topography analysis, and the geometry of englacial layers we identify potential subglacial flow pathways.

Our study focuses on a 350 km² region located 124 km upstream of the Thwaites Glacier grounding line, where an active subglacial lake has been inferred from satellite altimetry, reflecting periodic ice surface uplift and depression. We investigate the ice-bed interface reflectivity to identify areas of potential water accumulation or saturated sediments beneath the glacier. Additionally, we analyse the geometry of englacial layers to further explore subglacial water distribution and drainage patterns. To account for the influence of basal topography, we remove the topographic signal to derive layers relative to a "flattened" base. Residual englacial layers above regions of high bed reflectivity were examined for drawdowns and uplifts linked to subglacial hydrological processes.

We also simulate the hydropotential in this region to delineate the most likely drainage pathways around the active subglacial lake's fringe. Our findings reveal high bed reflectivity areas coinciding with englacial layer drawdowns, along with regions of apparent uplift in the englacial stratigraphy. These results suggest a potential flow routing for Subglacial Lake Thw 124 and indicate that its previously defined boundary may be overestimated, implying episodic lake growth.