Table 1 Parameters pertaining to ice flow and basal topography across each survey patch

From: Diverse landscapes beneath Pine Island Glacier influence ice flow

 

Mean basal shear stress (τ b)/kPa

Mean basal ice velocity (U b)/m a−1

Measured upstream propagation of thinning (P r)/km a−1

Inverted basal traction coefficient (β)

Dominant vertical height of topography/m

Typical width of streamlined features/m

Normalised across-flow roughness using a 2-km moving window

Normalised along-flow roughness using a 2-km moving window

iSTARt6

15

210

9

71

2–6

450–550

0.08 (new)0.10 (BM2)

0.001 (new)0.04 (BM2)

iSTARt1

16

320

11

50

2–3

100–300

0.77 (new)0.24 (BM2)

0.72 (new)0.04 (BM2)

2007t1

15

260

11

58

2–6

200–400

0.28 (new)0.09 (BM2)

0.04 (new)0.002 (BM2)

iSTARt5

19

300

13

63

3–6 (MSGL)100 (larger features)

500–800 (MSGL)5000 (larger features)

0.43 (new)0.24 (BM2)

0.07 (new)0.16 (BM2)

2010tr

18

430

12

42

5–10

300–400

0.18 (new)0.14 (BM2)

0.07 (new)0.08 (BM2)

2007tr

21

600

12

35

2–6

200–300

0.05 (new)0.08 (BM2)

0.04 (new)0 (BM2)

iSTARt7

78

232

8

336

5–10 (MSGL)25–50(larger features)

300–500 (MSGL)700–900(larger features)

0.13 (new/upstream)0.27 (new/downstream)0.22 (BM2)

0.02 (new)0.05 (BM2)

iSTARit

160

2

0

80,000

n/a

n/a

0.59 (new)0.17 (BM2)

0.90 (new)0.21 (BM2)

iSTARt9

130

138

6

942

5–12 (MSGL)50–80 (larger features)

300–600 (MSGL)600–1000 (larger features)

1 (new)0.22 (BM2)

0.67 (new)0.12 (BM2)

  1. FFT fast Fourier transform
  2. τ b and U b are the mean basal shear stress (kPa) and mean basal ice velocity (m a−1) from model inversion37; P r is the measured upstream propagation rate of ice thinning per ice-stream tributary from 1992 to 2015 using a thinning/non-thinning threshold of 1.0 m a−1 6 and β is the inverted basal traction coefficient equal to τ b/U b. Columns 6 and 7, respectively, list the dominant vertical heights (measured trough-to-crest) and typical widths of streamlined features; in the cases of patches iSTARt5, iSTARt7 and iSTARt9, two sets are listed, where the smaller values pertain to likely MSGL and the larger values pertain to the longer-wavelength lineations over which the MSGL are superimposed. Most lineations continue beyond the patch boundaries rendering us unable to provide typical lengths. Columns 8 and 9 list normalised FFT-derived roughness values retrieved from profiles taken across and along flow, respectively, using 2-km moving windows—see Methods summary for more details. For iSTARt7, two across-flow profiles were measured, one across the relatively flat upstream region and one across the higher elevation, rougher downstream portion
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