Preserved landscapes underneath the Antarctic Ice Sheet reveal the geomorphological history of Jutulstraumen Basin

Abstract

The landscape of Antarctica, hidden beneath kilometre-thick ice in most places, has been shaped by the interactions between tectonic and erosional processes. The flow dynamics of the thick ice cover deepened pre-formed topographic depressions by glacial erosion, but also preserved the subglacial landscapes in regions with moderate to slow ice flow. Mapping the spatial variability of these structures provides the basis for reconstruction of the evolution of subglacial morphology. This study focuses on the Jutulstraumen Glacier drainage system in Dronning Maud Land, East Antarctica.The Jutulstraumen Glacier reaches the ocean via the Jutulstraumen Graben, which is the only significant passage for draining the East Antarctic Ice Sheet through the western part of the Dronning Maud Land mountain chain. We acquired new bed topography data during an airborne radar campaign in the region upstream of the Jutulstraumen Graben to characterise the source area of the glacier. The new data show a deep relief to be generally under-represented in available bed topography compilations. Our analysis of the bed topography, valley characteristics and bed roughness leads to the conclusion that much more of the alpine landscape that would have formed prior to the Antarctic Ice Sheet is preserved than previously anticipated.We identify an active and deeply eroded U-shaped valley network next to largely preserved passive fluvial and glacial modified landscapes. Based on the landscape classification, we reconstruct the temporal sequence by which ice flow modified the topography since the beginning of the glaciation of Antarctica.

Evidence of Cascading Subglacial Water Flow at Jutulstraumen Glacier (Antarctica) Derived From Sentinel‐1 and ICESat‐2 Measurements

“…However, their analysis is solely based on radio-echo sounding (RES) surveys and the potential lake locations are restricted to the margins of the JG drainage basin. Ice thickness and bed topography have been extensively mapped in this region (Ferraccioli et al, 2005;Riedel et al, 2012;Steinhage et al, 1999Steinhage et al, , 2001 and indicate a spatially variable and preserved alpine landscape, which has been most likely generated by relief-controlled glacial erosion, sub-aerial weathering and fluvial erosion from mountain glaciers (Franke et al, 2021;Näslund, 2001).…”

“…We provide a description of the specific acquisition geometry and corresponding radar processing steps (Text S3) and refer to Hale et al (2016) and Rodriguez-Morales et al (2014) for further system specifics. The radar data cover areas that are not covered in Antarctic-wide ice thickness and bed topography maps (Fretwell et al, 2013;Morlighem et al, 2020), and we include this additional information to resolve the bed in our area of interest in finer detail (see also Franke et al, 2021, for further details on the data and methods used for the refined bed topography). The grid size of our refined bed topography is 1 km.…”

Bathymetric Control on Borchgrevink and Roi Baudouin Ice Shelves in East Antarctica

“…The landscape of DML has been shaped by tectonic processes as well as fluvial and glacial erosion. Inland of the region's coastal escarpments, the observation of subglacially preserved alpine landscapes connected with an intact and only slightly modified fluvial drainage system speaks for a period of alpine style glaciation before the formation of cold-based ice sheets (Eagles et al, 2018;Franke et al, 2021;Näslund, 2001). Seaward, the subglacial topography and bathymetry in DML suggests a different history, being characterized overall by gentle slopes crossed by overdeepened troughs with undulating valley profiles that terminate at prominent sills along the continental shelf break (Eisermann et al, 2020;Nøst, 2004;Smith et al, 2020).…”

“…This mountain chain ends seaward at a tall escarpment, the product of post-breakup erosional backwearing and downwearing. Over and inland of the mountains, the drainage system developed from a period of alpine style glaciation is still preserved beneath the ice and only slightly overprinted by later ice-sheet processes (Eagles et al, 2018;Franke et al, 2021;Näslund, 2001).…”

Airborne ultra-wideband radar sounding over the shear margins and along flow lines at the onset region of the Northeast Greenland Ice Stream

“…The transmitted electromagnetic waves are sensitive to changes in dielectric permittivity and electrical conductivity and get reflected, scattered, or refracted at interfaces of dielectric contrasts in the medium they propagate (Fujita et al, 1999). The most common glaciological application is the sounding of ice thickness and bed topography (e.g., Hempel and Thyssen, 1992;Dahl-Jensen et al, 1997;Steinhage et al, 1999;Nixdorf and Göktas, 2001;Kanagaratnam et al, 2001;Franke et al, 2021b). Reflections within the ice column, or so-called internal reflection horizons (IRHs), are often caused by impurity layers of volcanic origin representing isochronous horizons (Millar, 1981).…”