5.3 Future work 791
5.3.1 Methodological developments 793
794
Depending on the desired use and output of this method, several steps can be 795
undertaken to enhance the results, should they be required. For example, mapping 796
can be compared to geological maps, maps of water bodies and maps of other 797
subglacial bedforms (e.g. rogen moraines, tunnel valleys etc.) which may have been 798
misclassified as hummock corridors by the automatic method. Furthermore, visually 799
assessing the output in a GIS software will draw the eye to areas which are 800
particularly ‘blocky’ in nature and which clearly stand out. The user can then make 801
their own decision as to whether this information should be removed.
802
42
Visual assessment of the results suggests that misidentification is typically 803
associated with narrower features or additional features on the bed exhibiting strong 804
directional trends, such as fluvial channels in test site 3, or in some cases linear 805
tracts of drumlins. Future work may reduce the influence of this for example, by 806
trialling the code on different resolution data or by using different sized sample tiles.
807
Determining the scale at which the hummock corridors remain aligned may allow the 808
user to alter the input tile size as a way of reducing the likelihood of additional 809
directional features influencing the FFT filter.
810 811
5.3.2 Applications 812
813
Within the test sites, there is a clear association between hummock corridors and 814
section of northern Canada, we will be able to compare the general distribution and 820
pattern to that of eskers at an ice-sheet scale. The output of this can be used to 821
guide more detailed manual mapping, significantly reducing mapping time by 822
drawing the eye to areas of interest, after which the manual mapper can ‘fill in the 823
gaps’. While this method is yet to be tested on other features, theoretically it should 824
be possible to use our approach to identify other bedforms which share a predefined 825
horizontal size range and orientation. For example, it may be possible to alter the 826
parameters slightly and use this to map eskers or drumlins.
827
43 6. Conclusions
828 829
This work has been motivated by the large-scale release of high resolution 830
ArcticDEM data which allows subglacial bedforms to be mapped at an 831
unprecedented spatial and temporal scale. Hummock corridors have been widely 832
identified on the beds of palaeo-ice sheets, and the results of our automated 833
mapping method offer the potential to rapidly gain a large amount of information on 834
the morphological characteristics and large-scale distribution of hummock corridors.
835
This will add to the existing literature and can be used to inform the development of 836
hypotheses for hummock corridor formation.
837 838
Given the increasing availability of high-resolution data, there is a need to 839
develop new methods which can rapidly obtain meaningful information directly from 840
DEMs. While automatic mapping may never reach the same level of detail and 841
precision as manual mapping for individual bedforms, it has potential when the main 842
aim is to quantify the large-scale pattern of landforms. In this study, we add to an 843
increasing body of literature on the development of automatic methods for the 844
identification and mapping of palaeo-subglacial bedforms by developing the first 845
automatic method for extracting spatial information on hummock corridors. We apply 846
this method to three test sites across the ArcticDEM and demonstrate that hummock 847
corridors with varying expressions and varying background conditions can be 848
identified. Results suggest that our method can capture the general location and 849
spatial pattern/ distribution of hummock corridors and provides a decent ‘first pass’
850
map which can later be refined manually depending on the desired output.
851 852
44
For this study, the ability to correctly identify each hummock is less important 853
than the method’s ability to capture the location and overall pattern of corridors and 854
when considering a large sample size, the results (i.e. Table 5 – combined sites) 855
suggest that the automatic method can accurately characterise their morphology.
856
The next step will be to use this method to map hummock corridors using the 857
ArcticDEM data for Canada and northern Scandinavia, thus gaining unprecedented 858
insight into the large-scale distribution and pattern of hummock corridors and their 859
association with other subglacial bedforms and meltwater features. This will provide 860
evidence for formation theories as well as information which can be used to better 861
understand the distribution and nature of subglacial meltwater flow beneath former 862
and current ice-sheets.
863 864 865
7. Acknowledgements 866
867
This work was funded through “Adapting to the Challenges of a Changing 868
Environment” (ACCE); a NERC funded doctoral training partnership ACCE DTP 869
(NE/L002450/1). DEMs provided by the Polar Geospatial Centre under NSF-OPP 870
awards 1043681, 1559691, and 1542736. We would like to thank Sarah Greenwood 871
and Kang Yang for useful discussions. We would also like to thank Mike Smith, 872
Andrew Finlayson and the editor for their reviews that resulted in significant 873
improvements to the manuscript.
874 875 876 877
45 8. Data availability
878 879
The numerical code developed in this paper is archived at:
880
https://doi.org/10.15131/shef.data.7999445.
881 882
9. References 883
884
Anderson, R.S. et al., 2004. Strong feedbacks between hydrology and sliding of a 885
small alpine glacier. Journal of Geophysical Research. 109(F3).
886 887
Andrews, L.C. Catania, G.A. Hoffman, M.J. Gulley, J.D. Luthi, M.P. Ryser, C.
888
Hawley, R.L. Neumann, T.A. 2014. Direct observations of evolving subglacial 889
drainage beneath the Greenland Ice Sheet. Nature. 514(7520): 80-3.
890 891
Arrell, K. Wise, S. Wood, J. Donoghue, D. (2008). Spectral filtering as a method of 892
visualising and removing striped artefacts in digital elevation data. Earth 893
Processes and Landforms. 33(6): 943-61.
894 895
Baatz, M. Schäpe, A. (2000) Multiresolution Segmentation: An Optimization 896
Approach for High Quality Multi-Scale Image Segmentation. In: Strobl, J., 897
Blaschke, T. and Griesbner, G., Eds., Angewandte Geographische 898
Informations-Verarbeitung, XII, Wichmann Verlag, Karlsruhe, Germany, 12-899
23.
900 901
46
Bartholomew, I. Nienow, P. Mair, D. Hubbard, A. King, M.A. Sole, A. 2010. Seasonal 902
evolution of subglacial drainage and acceleration in Greenland outlet glacier.
903
Nature Geoscience. 3: 408-11.
904 905
Bishop, M.P. Allan James, L. Shroder, J.F. Walsh, S.J. (2012). Geospatial 906
technologies and digital geomorphological mapping: Concepts, issues and 907
research. Geomorphology. 137: 5-26.
908
Boulton, G.S. Clark, C.D. (1990). A highly mobile Laurentide Ice Sheet revealed by 909
satellite images of glacial lineations. Nature. 346: 813-17.
910
Boulton, G.S. Dobbie, K.E. Zatsepin, S. 2001. Sediment deformation beneath 911
glaciers and its coupling to the subglacial hydraulic system. Quaternary 912
International. 86: 3-28.
913 914
Burke, M.J. Brennand, T.A. Perkins, A.J. (2011). Erosional corridor evolution in 915
south-central British Columbia: insights from ground-penetrating radar 916
surveys. Proceedings of Geohydro 2011.
917 918
Chandler, D.M. Wadham, J.L. Lis, G.P. Cowton, T. Sole, A. Bartholomew, I. Telling, 919
J. Nienow, P. Bagshaw, E.B. Mair, D. Vinen, S. Hubbard, A. 2013. Evolution 920
of the subglacial drainage system beneath the Greenland Ice Sheet revealed 921
by tracers. Nature Geoscience. 6.
922
Clark, C.D. Evans, D.J.A. Khatwa, A. Bradwell, T. Jordan, C.J. Marsh, S.H. Mitchell, 923
W.A. Bateman, M.D. (2004). Map and GIS database of glacial landforms and 924
features related to the British Ice Sheet. Boreas. 33: 359-75.
925
47
Clark, C.D. Hughes, A.L.C. Greenwood, S.L. Jordan, C. Sejrup, H.P. (2012). Pattern 926
and timing of retreat of the last British-Irish Ice Sheet. Quaternary Science 927
Reviews. 44: 112-46.
928
Clark, C.D. Livingstone, S.J. (2018). Glacial curvilineations found along the southern 929
sector of the Laurentide Ice sheet and a hypothesis of formation involving 930
subglacial slope failure in tunnel valleys and subglacial lakes. Earth Surface 931
Processes and landforms. 43(7): 1518-1528.
932
Clark, P.U. Walder, J.S. (1994). Subglacial drainage, eskers and deforming beds 933
beneath the Laurentide and Eurasian ice sheets. Geol. Soc. Am. Bull. 106:
934
304-14.
935
d’Oleire-Oltmanns, S. Eisank, C. Dragut, L. Blaschke, T. (2013). An object-based 936
workflow to extract landforms at multiple scales from two distinct data types.
937
IEEE Geoscience and Remote Sensing Letters. 10(4): 947-51.
938
Dungan, J.L. (2002). Toward a comprehensive view of uncertainty in remote sensing 939
analysis. In Uncertainty in Remote Sensing and GIS, G.M. Foody and P.M.
940
Atkinson (Eds). Pp 25-35. (Chichester, UK: Wiley).
941
Dyke, A.S. Prest, V.K. (1987). Late Wisconsinan and Holocene history of the 942
Laurentide ice sheet. Geog. Phys. Quat. 41: 237-64.
943
Eisank, C. Smith, M.J. Hillier, J.K. (2014). Assessment of multiresolution 944
segmentation for delimiting drumlins in digital elevation models.
945
Geomorphology. 214: 452-64.
946
48
Evans, D.J.A. Clark, C.D. Mitchell, W.A. (2005). The last British Ice Sheet: a review 947
of the evidence utilised in the compilation of the Glacial Map of Britain. Earth 948
Science Reviews. 70: 253-312.
949
Evans, I.S. (2012). Geomorphometry and landform mapping: what is a landform?
950
Geomorphology. 137: 94-106.
951
Foroutan, M. Zimbelman, J.R. (2017). Semi-automatic mapping of linear-trending 952
bedforms using ‘Self-Organising Maps’ algorithm. Geomorphology. 293(A):
953
156-66.
954
Greenwood, S.L. Clark, C.D. (2008). Subglacial bedforms of the Irish Ice Sheet.
955
Journal of Maps. 4(1): 325-57.
956
Greenwood, S.L. Clark, C.D. Hughes, A. (2007). Formalising an inversion 957
methodology for reconstructing ice-sheet retreat patterns from meltwater 958
channels: application to the British Ice Sheet. Journal of Quaternary Science.
959
22: 637-45.
960
Haralick, R. Shapiro, L. (1985). Image segmentation techniques. Computer Vision, 961
Graphics, and Image Processing. 29: 100-32.
962
Hillier, J.K. Smith, M. (2008). Residual relief separation: digital elevation model 963
enhancement for geomorphological mapping. Earth Surface Processes and 964
Landforms. 33: 2266-76.
965
Hillier, J.K. Smith, M. Armugam, R. Barr, I. Boston, CM. Clark, C.D. Ely, J. Fankl, A.
966
Greenwood, S.L. Gosselin, L. Hättestrand, C. Hogan, K. Hughes, A.L.C.
967
Livingstone, S.J. Lovell, H. McHenry, M. Muñoz, Y. Pellicer, X.M. Pellitero, R.
968
49
Robb, C. Roberson, S. Ruther, D. Spagnolo, M. Standell, M. Stokes, C.R.
969
Storrar, R. Tate, N.J. Wooldridge, K. (2015). Manual mapping of drumlins in 970
synthetic landscapes to assess operator effectiveness. Journal of Maps.
971
11(5): 719-29.
972
Hillier, J.K. Watts, A.B. (2004). “Plate-like” subsidence of the East Pacific Rise-South 973
Pacific superswell system. Geomagnetism and Paleomagnetism/ Marine 974
Geology and Geophysics. 109(B10).
975
Hughes, A. Clark, C.D. Jordan, C. (2010). Subglacial bedforms of the last British ice 976
sheet. Journal of Maps. 543-63.
977
Iken, A. 1981. The effect of subglacial water pressure on the sliding velocity of a 978
glacier in an idealized numerical model. Journal of Glaciology. 27 (97): 407-979
21.
980 981
Jordan, G. Schott, B. (2005). Application of wavelet analysis to the study of spatial 982
pattern of morphotectonic lineaments in digital terrain models. A case study.
983
Remote Sensing of Environment. 94: 31-38.
984 985
Jorge, M.G. Brennand, T.A. (2017). Semi-automated extraction of longitudinal 986
subglacial bedforms from digital terrain models – Two new methods.
987
Geomorphology. 288: 148-63.
988
Kleman, J. (1992). The palimpsest glacial landscape in north-west Sweden.
989
Geografiska. 74A: 306-25.
990
50
Kleman, J. Borgstrom, I. (1996). Reconstruction of palaeo-ice sheets: the use of 991
geomorphological data. Earth Surface Processes and Landforms. 21: 893-992
909.
993
Kleman, J. Glasser, N.F. (2007). The subglacial thermal organisation (STO) of ice 994
sheets. Quaternary Science Reviews. 26(5-6): 585-97.
995
Livingstone, S.J. Clark, C.D. (2016). Morphological properties of tunnel valleys of the 996
southern sector of the Laurentide Ice Sheet and implications for their 997
formation. Earth Surface Dynamics. 4: 567-89.
998
Livingstone, S.J. Utting, D.J. Ruffell, A. Clark, C.D. Pawley, S. Atkinson, N. Fowler, 999
A.C. (2016). Discovery of relict subglacial lakes and their geometry and 1000
mechanism of drainage. Nature Communications. 7. 11767.
1001
Makinen, J. Kajuutti, K. Palmu, J.-P. Ojala, A. Ahokangas, E. (2017). Triangular-1002
shaped landforms reveal subglacial drainage routes in SW Finland.
1003
Quaternary Science Reviews. 164: 37-53.
1004
Margold, M. Jansson, K.N. Kleman, J. Stroeven, A.P. Clague, J.J. (2013). Retreat 1005
pattern of the Cordilleran Ice Sheet in central British Columbia at the end of 1006
the last glaciation reconstructed from glacial meltwater landforms. Boreas. 42:
1007
830-47.
1008
Margold, M. Stokes, C.R. Clark, C.D. (2015). Ice streams in the Laurentide Ice 1009
Sheet: Identification, characteristics and comparison to modern ice sheets.
1010
Earth Science Reviews. 143: 117-46.
1011
51
Munch, B. Trtik, P. Marone, F. Stampanoni, M. (2009). Stripe and ring artefact 1012
removal with combined wavelet – Fourier filtering. Optic Express. 17(10):
1013
8567-91.
1014
Noh, M-J. Howat, I.M. (2015). Automated stereo-photogrammetric DEM generation 1015
at high latitudes: Surface Extraction with TIN-based Search-space 1016
Minimization (SETSM) validation and demonstration over glaciated regions.
1017
GIScience and Remote Sensing. 52(2): 198-217.
1018
Ó Cofaigh, C., Stokes, C.R. (2008). Reconstructing ice-sheet dynamics from 1019
subglacial sediments and landforms: introduction and overview. Earth Surface 1020
Processes and Landforms 33(4): 495-502.
1021
Otsu, N. (1979). A threshold selection method from gray-level histograms. IEEE 1022
Transactions on Systems, Man, and Cybernetics. SMC-9.
1023
Ottesen, D. Stokes, C.R. Rise, L. Olsen, L. (2008). Quaternary ice-sheet dynamics 1024
and ice streaming along the coastal parts of northern Norway. Quaternary 1025
Science Reviews. 27: 19.
1026
Peterson, G. Johnson, M.D. Colby, A. Smith. (2017). Glacial geomorphology of the 1027
south Swedish uplands – focus on the spatial distribution of hummock tracts.
1028
Journal of Maps. 13(2): 534-44.
1029
Peterson, G. Johnson, M.D. Dahlgren, S. Passe, T. Alexanderson, H. (2018).
1030
Genesis of hummocks found in tunnel valleys: an example from Hörda, 1031
southern Sweden. GFF. 140(2): 189-201.
1032
52
Peterson, G. Johnson, M.D. (2018). Hummock corridors in the south-central sector 1033
of the Fennoscandian ice sheet, morphometry and pattern. Earth Surface 1034
Processes and Landforms. 43: 919-29.
1035
Pratomo, J. Kuffer, M. Martinez, J. Kohli, D. (2017). Coupling uncertainties with 1036
accuracy assessment in object-based slum detection case study: Jakarta, 1037
Indonesia. Remote Sensing. 9(11).
1038
Rampton, V.N. (2000). Large-scale effects of subglacial meltwater flow in the 1039
southern Slave Province, Northwest Territories, Canada. Canadian Journal of 1040
Earth Sciences. 37(1): 81–93.
1041 1042
Ryherd, S. Woodcock, C.E. (1996). Combining spectral and texture data in the 1043
segmentation of remotely sensed images .Photogrammetric Wngineering and 1044
Remote Sensing. 62(2): 181-94.
1045 1046
Saha, K. Wells, N.A. Munro-Stasiuk, M. (2011). An object-orientated approach to 1047
automated landform mapping: A case study of drumlins. Computers and 1048
Geosciences. 37(9): 1324-36.
1049 1050
Schoof, C., 2010. Ice-sheet acceleration driven by melt supply variability. Nature.
1051
468(7325): 803–6.
1052 1053
Sharp, M. Gemmel, J. Tison, J. (1989). Structure and stability of the former 1054
subglacial drainage system of the Glacier de Tsanfleuron, Switzerland. Earth 1055
Surface Processes and Landforms. 14(2): 119-134.
1056
53 1057
Sharpe, D. Kjarsgaard, B. Knight, R.D. Russell, H.A.J. Kerr, D.E. (2017). Glacial 1058
dispersal and flow history, East Arm area of Great Slave Lake, NWT, Canada.
1059
Quaternary Science Reviews. 165: 49-72.
1060 1061
Sjogren, D.B. Fisher, T.G. Taylor, L.D. Jol, H.M. Munro-Stasiuk, M.J. 2002. Incipient 1062
tunnel channels. Quaternary International. 90: 41-56.
1063 1064
Smith, M.J. Clark, C.D. (2005). Methods for the visualisation of digital elevation 1065
models for landform mapping. Earth Surface Processes and Landforms.
1066
30(7): 885-900.
1067 1068
Spagnolo, M. Bartholomaus, T.C. Clark, C.D. Stokes, C.R. Atkinson, N. Dowdeswell, 1069
J.A. Ely, J.C. Graham, A.G.C. Hogan, K.A. King, E.C. Larter, R.D.
1070
Livingstone, S.J. Pritchard, H.D. (2017). The periodic topography of ice 1071
stream beds: Insights from the Fourier spectra of mega-scale glacial 1072
lineations. Journal of Geophysical Research: Earth Surface. 122(7): 1355-1073
1373.
1074
Stehman, S.V. Wickham, J.D. (2011). Pixels, blocks of pixels, and polygons:
1075
Choosing a spatial unit for thematic accuracy assessment. Remote Sensing of 1076
the Environment. 115(12): 3044-55.
1077
Stokes, C.R. Clark, C.D. (1999). Geomorphological criteria for identifying Pleistocene 1078
ice streams. Annals of Glaciology. 28: 67-74.
1079
54
Stokes, C.R. et al., (2015). On the reconstruction of palaeo-ice sheets: Recent 1080
advances and future challenges. Quaternary Science Reviews. 125: 15-49.
1081
St-Onge, 1984. Surficial deposits of the Redrock Lake area, District of Mackenzie; in 1082
Current Research, Part A, Geological Survey of Canada, Paper 84 (1A): 271-1083
78.
1084 1085
Storrar, R.D. Livingstone, S.J. (2017). Glacial geomorhology of the northern Kivalliq 1086
region, Nunavut, Canada, with an emphasis on meltwater drainage systems.
1087
Journal of Maps. 13(2): 153-64.
1088
Storrar, R.D. Stokes, C.R. Evans, D.J.A. (2014). Increased channelisation of 1089
subglacial drainage during deglaciation of the Laurentide Ice Sheet. Geology.
1090
42(3): 239-42.
1091
Storrar, R.D. Stokes, C.R. Evans, D.J.A. (2014). Morphometry and pattern of a large 1092
sample (>20,000) of Canadian eskers and implications for subglacial drainage 1093
beneath ice sheets. Quaternary Science Reviews. 105: 1-25.
1094
Tedstone, A.J. Nienow, P.W. Gourmelon, N. Dehecq, A. Goldberg, D. Hanna, E.
1095
2015. Decadal slowdown of a land-terminating sector of the Greenland Ice 1096
Sheet despite warming. Nature. 526: 692-695.
1097
Tsai, D.M. Hsieh, C.Y. (1999). Automated surface inspection for directional textures.
1098
Image and Vision Computing. 18:49-62.
1099
Utting, D.J., Ward, B.C. & Little, E.C. (2009). Genesis of hummocks in glaciofluvial 1100
corridors near the Keewatin Ice Divide, Canada. Boreas. 38(3): 471–481.
1101
55 1102
Van Buren, D. (1987). Fourier removal of stripe artefacts in IRAS images.
1103
Astronomical Journal. 94: 1092- 94.
1104
Van der Vegt, P. Janszen, A. Moscariello, A. (2012). Tunnel Valleys: current 1105
knowledge and future perspectives. In: Husse, M. Reddfern, J. Le Heron, D.P.
1106
Dixon, R.J. Moscariello, A. Craig, J. (Eds), Glaciogenic Reservoirs and 1107
Hydrocarbon Systems. Geological Society Special Publication, vol. 368: 75-1108
97.
1109
Wessel, P. (1998). An empirical method for optimal robust regional-residual 1110
separation of geophysical data. Journal of Mathematical Geology. 30(4): 391-1111
408.
1112
Williams, C. O’Leary, M. Luckman, A. J́hannesson, T. Murray, T. (2018).
1113
Automated crevasse mapping: assisting with mountain and glacier hazard 1114
assessment. Geophysical Research Abstracts. Vol. 20. EGU2018-5137.
1115
Wright, H.E. (1973). Tunnel valleys, glacial surges and subglacial hydrology of the 1116
Superior Lobe, Minnesota. In: Black, R.F. Goldthwait, R.P. and Willman, H.B.
1117
(eds.) The Wisconsian Stage. Geological Society of America, Memoir. 136:
1118
251-76.
1119 1120
Yu, P. Eyles, N. Sookhan, S. (2015). Automated drumlin shape and volume 1121
estimation using high resolution LiDAR imagery (Curvature Based Relief 1122
Separation): A test from the Wadena Drumlin Field, Minnesota.
1123
Geomorphology. 246: 589-601.
1124
56 1125
Zhang, X. Feng, X. Xiao, P. He, G. Zhu, L. (2015). Segmentation quality evaluation 1126
using region-based precision and recall measures for remote sensing. ISPRS 1127
Journal of Photogrammetry and Remote Sensing. 102: 73-84.
1128