Using bed-roughness signatures to characterise glacial landform assemblages beneath palaeo-ice sheets

Abstract

Palaeo-glacial landforms can give insights into bed roughness that currently cannot be captured underneath contemporary-ice streams. A few studies have measured bed roughness of palaeo-ice streams but the bed roughness of specific landform assemblages has not been assessed. If glacial landform assemblages have a characteristic bed-roughness signature, this could potentially be used to constrain where certain landform assemblages exist underneath contemporary-ice sheets. To test this, bed roughness was calculated along 5 m × 5 m resolution transects (NEXTMap DTM, 5 m resolution), which were placed over glacial landform assemblages (e.g. drumlins) in the UK. We find that a combination of total roughness and anisotropy of roughness can be used to define characteristic roughness signatures of glacial landform assemblages. The results show that different window sizes are required to determine the characteristic roughness for a wide range of landform types and to produce bed-roughness signatures of these. Mega scale glacial lineations on average have the lowest bed-roughness values and are the most anisotropic landform assemblage.

Glacier geometry limits the propagation of thinning in Patagonian Icefields

“…According to our results, these gradient changes limit the propagation of the thinning from the terminus. Previous research has shown that bed roughness is important in controlling glacier dynamics (Falcini et al, 2022) and ice flow resistance (Hoffman et al, 2022). Roughness is generally found to be associated with the presence of hills, valleys, and bumps under the ice.…”

“…This highlights the importance of combining bed geometric analysis with lithological variability. On the other hand, ice flow can smooth the bed and consequently generate substantial changes in glacier dynamics (Falcini et al, 2022).…”

Antarctic subglacial topography mapped from space reveals complex mesoscale landscape dynamics

“…To address these uncertainties, many studies have sought to use landscapes left behind by former ice sheets to inform model-parameter choices [9][10][11]. High-resolution surveys of these deglaciated landscapes clearly depict substrates whose roughness and deformability vary considerably over the several-km scale that previous work has shown is crucial to determine rates of ice flow and glacial retreat under climate forcing [12][13][14][15]. Across Antarctica, limited geological exposures in exposed, subaerial mountain ranges and around the margins offer some insights into the properties of the buried bed [16], but the majority of what is known about the ice-bed interface across the Antarctic interior comes from geophysical surveys [17][18][19][20][21].…”