Figure 1.
Overview map of the Khumbu region (April 2013 Landsat) showing Tsho Rolpa Lake (NW-flowing Trakarding glacier) in the Rowaling Valley; Spillway Lake (SE-flowing Ngozumpa glacier) in the Gokyo Valley; and Imja Lake (W-flowing Imja glacier) in the Khumbu Valley.
Figure 1.
Overview map of the Khumbu region (April 2013 Landsat) showing Tsho Rolpa Lake (NW-flowing Trakarding glacier) in the Rowaling Valley; Spillway Lake (SE-flowing Ngozumpa glacier) in the Gokyo Valley; and Imja Lake (W-flowing Imja glacier) in the Khumbu Valley.
Figure 2.
Ngozumpa glacier’s terminal moraine and western outlet stream. Boulders along the outlet are a testament to previous floods in the area.
Figure 2.
Ngozumpa glacier’s terminal moraine and western outlet stream. Boulders along the outlet are a testament to previous floods in the area.
Figure 3.
The evolution of Spillway Lake’s sub-basins since 2001 (
A) and depth map from the original 2009/2010 survey work (
B). Adapted from [
4], with permission from © Elsevier (
Geomorphology).
Figure 3.
The evolution of Spillway Lake’s sub-basins since 2001 (
A) and depth map from the original 2009/2010 survey work (
B). Adapted from [
4], with permission from © Elsevier (
Geomorphology).
Figure 4.
2016 GeoEye high-resolution image of Ngozumpa glacier (A) with Spillway Lake close-up (B), showing temperature buoy locations for this study in the sub-basins (yellow: northwest; green: northeast; red: main; blue: southwest), weather station (white square) and glacier outlet channel (yellow arrow).
Figure 4.
2016 GeoEye high-resolution image of Ngozumpa glacier (A) with Spillway Lake close-up (B), showing temperature buoy locations for this study in the sub-basins (yellow: northwest; green: northeast; red: main; blue: southwest), weather station (white square) and glacier outlet channel (yellow arrow).
Figure 5.
Vertical temperature and turbidity variations in the NW (A,B), NE (C,D) and Main sub-basin (E,F). The blue line is indicative of morning averages, while the black dotted line represents afternoon averages.
Figure 5.
Vertical temperature and turbidity variations in the NW (A,B), NE (C,D) and Main sub-basin (E,F). The blue line is indicative of morning averages, while the black dotted line represents afternoon averages.
Figure 6.
Annual temperatures at the surface (in blue), middle (in green), and bottom (in red) for each sub-basin from 01 June 2013 to 01 June 2014. (A) NW buoy; (B) NE buoy; (C) MB (Main basin) buoy; and (D) SW buoy. The arrows in each show the arrival of Cyclone Phailin (October 2013).
Figure 6.
Annual temperatures at the surface (in blue), middle (in green), and bottom (in red) for each sub-basin from 01 June 2013 to 01 June 2014. (A) NW buoy; (B) NE buoy; (C) MB (Main basin) buoy; and (D) SW buoy. The arrows in each show the arrival of Cyclone Phailin (October 2013).
Figure 7.
Seasonal temperature variations in the Main sub-basin buoy location for the summer/monsoon (A), fall (B), winter (C) and spring (D). Surface in blue; middle in green; bottom in red.
Figure 7.
Seasonal temperature variations in the Main sub-basin buoy location for the summer/monsoon (A), fall (B), winter (C) and spring (D). Surface in blue; middle in green; bottom in red.
Figure 8.
Seasonal temperature variations in the SW sub-basin buoy location for the summer/monsoon (A), fall (B), winter (C) and spring (D). Surface in blue; middle in green; bottom in red.
Figure 8.
Seasonal temperature variations in the SW sub-basin buoy location for the summer/monsoon (A), fall (B), winter (C) and spring (D). Surface in blue; middle in green; bottom in red.
Figure 9.
Air temperatures (A) and solar radiation (C) during May 2014. Temperatures do not reach their peak until later in the month. Solar radiation remains high (>1000 W/m2) during the month, but the 26 May snowstorm drops this to <400 W/m2. Zoom-ins of the NE buoy location (B) and the Main buoy location (D) for May 2014 show anomalous bottom water temperatures on 23 May.
Figure 9.
Air temperatures (A) and solar radiation (C) during May 2014. Temperatures do not reach their peak until later in the month. Solar radiation remains high (>1000 W/m2) during the month, but the 26 May snowstorm drops this to <400 W/m2. Zoom-ins of the NE buoy location (B) and the Main buoy location (D) for May 2014 show anomalous bottom water temperatures on 23 May.
Figure 10.
Surface (blue), middle (green) and bottom (red) water temperatures for NW (A) and SW (B) buoy locations. Pressure transducer data reveal a steady rise in water level at the SW site during the spring thaw, with a more chaotic gain seen in NW.
Figure 10.
Surface (blue), middle (green) and bottom (red) water temperatures for NW (A) and SW (B) buoy locations. Pressure transducer data reveal a steady rise in water level at the SW site during the spring thaw, with a more chaotic gain seen in NW.
Figure 11.
Ice melt (meters) for the sub-basins during the summer (blue), fall (orange), winter (black) and spring (green), using 1 cm of debris thickness.
Figure 11.
Ice melt (meters) for the sub-basins during the summer (blue), fall (orange), winter (black) and spring (green), using 1 cm of debris thickness.
Figure 12.
Air temperatures (A) and surface (blue), bottom (red) water temperatures and debris (black) temperatures (B) were measured in the Main sub-basin from June–October 2014.
Figure 12.
Air temperatures (A) and surface (blue), bottom (red) water temperatures and debris (black) temperatures (B) were measured in the Main sub-basin from June–October 2014.
Figure 13.
Sample sonar image from the Main sub-basin of Spillway Lake, showing the primary echo (E1 layer), which measures roughness (the signal can be mirrored back or take a multi-path), and the secondary (peak Sv layer) echo, which measures hardness based on the material’s acoustic absorption. The former shows sonar returns corresponding with color-coded dots. The darker, the rougher, in a relative scale.
Figure 13.
Sample sonar image from the Main sub-basin of Spillway Lake, showing the primary echo (E1 layer), which measures roughness (the signal can be mirrored back or take a multi-path), and the secondary (peak Sv layer) echo, which measures hardness based on the material’s acoustic absorption. The former shows sonar returns corresponding with color-coded dots. The darker, the rougher, in a relative scale.
Figure 14.
NE sub-basin roughness and hardness maps, generated from E1 and peak Sv acoustic backscatter values. Scaled smooth (A), rough (B), soft (C) and hard (D) are shown, with boxes overlain to show smooth-hard returns, interpreted to be bare ice.
Figure 14.
NE sub-basin roughness and hardness maps, generated from E1 and peak Sv acoustic backscatter values. Scaled smooth (A), rough (B), soft (C) and hard (D) are shown, with boxes overlain to show smooth-hard returns, interpreted to be bare ice.
Figure 15.
Main sub-basin roughness and hardness maps, generated from E1 and peak Sv acoustic backscatter values. Smooth (A), rough (B), soft (C) and hard (D) are shown, with boxes overlain to show smooth-hard returns (A,D), interpreted to be bare ice.
Figure 15.
Main sub-basin roughness and hardness maps, generated from E1 and peak Sv acoustic backscatter values. Smooth (A), rough (B), soft (C) and hard (D) are shown, with boxes overlain to show smooth-hard returns (A,D), interpreted to be bare ice.
Table 1.
Major and trace (As) elements and suspended sediment concentration (SSC) values from locations in and around Spillway Lake.
Table 1.
Major and trace (As) elements and suspended sediment concentration (SSC) values from locations in and around Spillway Lake.
Samples | Si (ppm) | Fe (ppm) | Mg (ppm) | Ca (ppm) | Al (ppm) | Na (ppm) | As (ppm) | SSC (g/L) |
---|
NW basin | 14.88 | 7.00 | 2.80 | 10.43 | 8.00 | 12.10 | 13.465 | 0.43 |
NW inflow | 18.64 | 0.15 | 0.24 | 12.93 | 0.31 | 0.61 | 10.873 | 0.22 |
Ice wall | 4.32 | 0.12 | 0.08 | 0.64 | 0.20 | 0.23 | DL | 0.07 |
NE basin | 20.81 | 5.62 | 1.93 | 10.73 | 10.03 | 16.23 | 13.763 | 0.21 |
NE inflow | 12.93 | 0.02 | 0.33 | 15.73 | 0.04 | 0.34 | 0.880 | 0.06 |
Main basin | 16.57 | 4.69 | 1.71 | 10.00 | 8.00 | 25.13 | 16.363 | 0.40 |
SW basin | 22.18 | 6.18 | 2.14 | 11.15 | 10.99 | 19.77 | 14.393 | 0.40 |
Outflow | 15.96 | 6.00 | 3.00 | 11.08 | 9.00 | 13.60 | 14.681 | 0.46 |
Blue lake | 2.92 | 0.19 | 0.27 | 20.06 | 0.40 | 19.73 | 45.456 | 0.04 |
Table 2.
Water properties for the sub-basins of Spillway Lake. Values of pH and conductivity were averaged with depth.
Table 2.
Water properties for the sub-basins of Spillway Lake. Values of pH and conductivity were averaged with depth.
Sub-basin | pH | Conductivity (µS) | Optical Depth (cm) |
---|
NW basin | 8.59 | 68.87 | 18 |
NE basin | 8.39 | 70.37 | 32 |
Main basin | 8.21 | 69.23 | 17.5 |
SW basin | 8.32 | 68.47 | 15 |
Table 3.
Seasonal ice melt rates (m/yr) for the sub-basins, with simulated debris thicknesses.
Table 3.
Seasonal ice melt rates (m/yr) for the sub-basins, with simulated debris thicknesses.
Sub-basin | Debris Thickness (m) | Seasonal Bottom Ice Melt (in Meters) |
---|
Summer (m) | Fall (m) | Winter (m) | Spring (m) |
---|
NW sub-basin | 0.01 | 2.1 | 2.92 | 0.51 | 0.37 |
0.02 | 1.05 | 1.46 | 0.26 | 0.19 |
0.05 | 0.42 | 0.58 | 0.1 | 0.07 |
0.1 | 0.21 | 0.29 | 0.05 | 0.04 |
0.15 | 0.14 | 0.19 | 0.03 | 0.02 |
0.3 | 0.07 | 0.1 | 0.02 | 0.01 |
0.5 | 0.04 | 0.06 | 0.01 | 0.01 |
1 | 0.02 | 0.03 | 0.01 | 0 |
Main sub-basin | 0.01 | 3.23 | 4.53 | 2.66 | 3.02 |
0.02 | 1.6 | 2.25 | 1.31 | 1.51 |
0.05 | 0.64 | 0.9 | 0.52 | 0.52 |
0.1 | 0.32 | 0.45 | 0.26 | 0.3 |
0.15 | 0.21 | 0.3 | 0.17 | 0.2 |
0.3 | 0.11 | 0.15 | 0.09 | 0.1 |
0.5 | 0.06 | 0.09 | 0.05 | 0.06 |
1 | 0.03 | 0.04 | 0.03 | 0.03 |
NE sub-basin | 0.01 | 4.42 | 5.39 | 2.84 | 3.18 |
0.02 | 2.21 | 2.67 | 1.4 | 1.58 |
0.05 | 0.88 | 1.07 | 0.56 | 0.63 |
0.1 | 0.44 | 0.53 | 0.28 | 0.32 |
0.15 | 0.29 | 0.36 | 0.19 | 0.21 |
0.3 | 0.15 | 0.18 | 0.09 | 0.11 |
0.5 | 0.09 | 0.11 | 0.06 | 0.06 |
1 | 0.04 | 0.05 | 0.03 | 0.03 |
SW sub-basin | 0.01 | 6.58 | 5.71 | 2.02 | 3.37 |
0.02 | 3.29 | 2.85 | 1.01 | 1.68 |
0.05 | 1.32 | 1.14 | 0.4 | 0.67 |
0.1 | 0.66 | 0.57 | 0.2 | 0.34 |
0.15 | 0.44 | 0.38 | 0.13 | 0.22 |
0.3 | 0.22 | 0.19 | 0.07 | 0.11 |
0.5 | 0.13 | 0.11 | 0.04 | 0.07 |
1 | 0.07 | 0.06 | 0.02 | 0.03 |