Table 1 Summary of borehole englacial debris concentrations and estimated ice column debris thickness, by site.

From: Continuous borehole optical televiewing reveals variable englacial debris concentrations at Khumbu Glacier, Nepal

 

Facies

Site 1

Site 2

Site 3

Site 4

Units

Low (0.0083% by volume)

1

26.8

98.1

88.2

95.6

% of OPTV image area

Medium (5.5% by volume)

2a

58.3

1.8

11.4

3.7

High (15% by volume)

2b

13.0

0.2

0.5

0.7

Very high (65% by volume)

3

1.9

0

0

0

Mean borehole englacial debris concentration

6.4

0.1

0.7

0.3

% by volume

OPTV log length (visible image)

27.0

20.1

147.4

134.4

m

Equivalent debris layer thickness from borehole ice deptha

2.6

0.04

1.5

0.6

Estimated full ice thicknessb

46

225

337

252

Equivalent debris layer thickness from estimated full ice thicknessa

4.4

0.4

3.5

1.2

m

  1. Uncertainties in the category debris concentrations, and therefore the mean borehole debris concentrations and thicknesses, are estimated to be ±50% (Methods). The estimates presented exclude basal debris or any additional debris layers, such as buried rockfall deposits, that could not be penetrated by the hot-water drill28. Bolding indicates key values derived by our analyses.
  2. aThickness of the supraglacial debris layer that would result from melting the borehole length or full ice column (as indicated), assuming no debris redistribution at the surface and a bulk effective porosity of 0.33 (ref. 31). Calculations are provided the 'Methods' section.
  3. bIce thicknesses are model outputs27, except for Site 1 where the neighbouring borehole was considered to have reached the bed28,33
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