Greenhouse to Icehouse Landscape Evolution Revealed in the Gamburtsev Subglacial Mountains, East Antarctica

Coupled ice-sheet and climate models predict that the Gamburtsev Subglacial Mountains (hereafter, Gamburtsevs) were a key nucleation site for the East Antarctic Ice Sheet (EAIS), 34 million years ago. However, evidence for the scale and shape of the EAIS since its inception is limited and generally restricted towards present-day ice sheet margins. We use recent airborne radar data from the AGAP project to examine the interplay between fluvial and glacial processes in the Gamburtsev Province of East Antarctica. We hypothesise that the geometry of this landscape records the behaviour of both fluvial and glacial processes and the impact of long-term climate evolution. To understand and quantify the processes, patterns, and scales of landscape evolution across the Gamburtsevs, a range of morphometric tools, including power-law analysis and GIS, were employed. Bed elevation maps expose the high-relief Alpine-type morphology of the Gamburtsevs and reveal a network of dendritic valleys incised across the mountain range. Valley geometries and river-long profiles indicate widespread survival of a fluvial landscape that is likely to pre-date ice sheet initiation at 34 Ma, with some basins showing evidence for local-scale glaciation. Glacial overdeepening, towards the margins of the Gamburtsevs, suggests a regional-scale glacial signal has also been preserved. The preservation of these landscape signals reflects the poor erosive capabilities of the present day, continental-scale, ice sheet and suggests that it has remained relatively stable since its formation ca. 14 Ma. As such, the Gamburtsevs reveal a unique record of four different stages of landscape evolution, possibly representing the oldest glacial geomorphic record ever found.