Fig 1.
Left: Satellite image of the Dry Valleys region derived from the Landsat Image Mosaic of Antarctica (LIMA).
The Labyrinth is indicated with a white arrow. Inset at bottom left shows location of the Dry Valleys in Antarctica. Inset at the top right shows a close up of the Labyrinth with the two channels presented in this study highlighted in white. Right: Digital Elevation Model extracted from LiDAR data showing the axis of two subglacial cannels (channel A-B and C-D). Confluences of smaller channels into the two channels are indicated with numbers. In red the cross section used in the model. The black arrows indicate the flow direction.
Fig 2.
a) Typical cross section in the Labyrinth, Antarctica, derived from the LiDAR survey (black line) and the trapezoidal cross section adopted in the model (dotted red lines). The location of the cross section is indicated in red in Fig 1; b) glacier thickness profile reconstructed by Hall and Denton (2005) in the eastern Wright Valley, Antarctica.
Fig 3.
Illustration of a subglacial bedrock channel.
Bedrock is present at three sides (brown; side closest to viewer not shown) and the glacier’s bottom provides an ice roof to the channel (white). Parameters shown are water depth, d, and channel width, w. The channel is completely filled with water (blue) that transports saltating (curved arrows) and suspended sediment (straight arrows).
Table 1.
Constants.
Fig 4.
A) Water pressure, B) channel depth, and C) velocity along a subglacial channel for a discharge ranging from 2000 to 40000 m3/s. Distances are measured increasing upstream of the glacier’s snout. Different color lines represent different discharges.
Fig 5.
A) Sediment transport capacity along channel length for various water discharges. Ds = 10 cm and qs = 40 kg/m/s; B) Sediment transport capacity for various grain size diameters. Q = 20000 m3/s, qs = 40 kg/m/s.
Fig 6.
(A) Erosion rate along channel length for different water discharges. Ds = 10 cm and qs = 40 kg/m/s. (B) Erosion rate along channel length for different sediment supplies per unit width. Q = 20000 m3/s, Ds = 10 cm (C) Erosion rate for different grain size diameter of the sediments. Q = 20000 m3/s, qs = 40 kg/m/s.
Fig 7.
A) Maximum erosion rate along the channel as a function of sediment supply per unit width and water discharge. Ds = 10 cm. B) Maximum erosion rate along the channel as a function of sediment grain size and water discharge. qs = 40 kg/m/s.
Fig 8.
Evolution of a subglacial channel in time: A) erosion rate; B) bottom elevation. At the beginning of the simulations the channel has constant width (100m) and constant bottom elevation. Q = 20000 m3/s Ds = 10cm qs = 40 kg/m/s.
Fig 9.
Distribution of erosion rates in a subglacial channel before and after a confluence with another channel.
The dashed line is the erosion rate with the initial discharge and sediment load of the main channel, the black arrow is the location where the secondary channel discharges water and sediments, dotted line is the erosion rate with the final sediment discharge and sediment load (sum of the contribution of the two channels), the red line is the distribution of erosion rate before and after the confluence. In A) and B) the secondary channel is adding only water in the main channel while in C) and D) it is also adding sediment load. In A) and C) the erosion rate is higher after the confluence while in B) and D) it is lower.
Fig 10.
Depth, bottom elevation, and bottom gradient of the two subglacial channels indicated in Fig 1 (channel A-B and channel C-D).
The numbers refer to lateral tributaries discharging in the main trunk (see Fig 1). The red lines are a second order polynomial interpolation of the bottom elevation (parabola).
Fig 11.
Change in channel width and depth after a junction for channels A-B and C-D in Fig 1.
Positive values mean an increase in width and depth. The numbers refer to lateral tributaries discharging in the main trunk (see Fig 1).
Fig 12.
Bottom elevation gradient before and after each junction for channels A-B and C-D in Fig 1.
The numbers refer to lateral tributaries discharging in the main trunk. Negative is defined as upstream.