Paleofluvial and subglacial channel networks beneath Humboldt Glacier, Greenland

Abstract

The identification of subglacial drainage systems can inform our understanding of past and present hydrological processes, landscape evolution, and ice dynamics. Here, we present evidence from satellite imagery, digital elevation models, and radio-echo sounding data for a series of channelized networks with contrasting paleofluvial and subglacial origins beneath Humboldt Glacier, northern Greenland. A >250-km-long, dendritic paleofluvial channel network beneath the northern portion of Humboldt is interpreted as a preglacial feature. Roughly linear channels beneath the southern portion of Humboldt, which display a similar distribution to tunnel valleys found on the beds of former ice sheets, are likely to have been eroded by subglacial meltwater routed along the ice-sheet bed. We suggest that basal meltwater is actively being routed down both the paleofluvial and subglacially formed channel networks to the coast. Inheritance of the preglacial channel network may have influenced the present-day location and dynamics of Humboldt Glacier and enhanced selective erosion at its down-glacier end.

Self-affine subglacial roughness: consequences for radar scattering and basal water discrimination in northern Greenland

“…More generally, however, the relative rarity of high abruptness in thawed regions is in agreement with hydrological potential analysis (Livingstone et al, 2013), which predicts that deep subglacial lakes are both rare and small in the north-west of the GrIS. Instead, channelised drainage networks -such as the system recently identified beneath Humboldt glacier (Livingstone et al, 2017) -are likely to be common in thawed regions (and are consistent with the generally diffuse scattering signature that we observe).…”

“…For Greenland, this self-affine statistical landscape classification could be integrated with existing knowledge of geology (e.g. Henriksen, 2008) and larger-scale landscape features including subglacial drainage networks (Cooper et al, 2016;Chu et al, 2016;Livingstone et al, 2017) and palaeofluvial canyons (such the "mega canyon" feature observed in Fig. 6e, which has Petermann glacier as its modern-day terminus) (Bamber et al, 2013b).…”

A constraint upon the basal water distribution and basal thermal state of the Greenland Ice Sheet from radar bed-echoes

“…This includes the dendritic flow path networks in the Jakobshavn (Cooper et al, 2016) and Humboldt catchments (Livingstone et al, 2017), along with the prominent…”

“…10(b)) can potentially be linked to our understanding of the seasonal evolution of the subglacial drainage system. Specifically, in regions where there is 550 significant surface melt-water forcing, efficient channelised drainage systems can form during the summer months, which can result in a substantial lack of winter-time water storage in faster moving subglacial troughs (Chu et al, 2016).…”

Ice‐margin fluctuation sequences and grounding zone wedges: The record of the Late Palaeozoic Ice Age in the eastern Karoo Basin (Dwyka Group, South Africa)

“…The presence of vertical walls undoubtedly indicates that the structural heritage had a preponderant influence in the shaping of the basement. Moreover, a pre‐existing network of fluvial valleys was potentially reworked and amplified by direct glacial abrasion (von Brunn, , ), as is the case for some Quaternary high‐latitude valleys that originated from the combination of both pre‐glacial fluvial and glacial erosion processes (Lajeunesse, ; Livingstone et al , ). Indeed, the major hiatus that separates the basement from the Dwyka Group suggests that the study area constituted an emerged domain during pre‐Dwyka times as a result of crustal uplift preceding the inception of the Karoo Basin and the onset of glaciation (Visser, ; Tankard et al , ) and onto which a fluvial system may well have developed.…”