Flow-stripes and foliations of the Antarctic ice sheet

Ely, Jeremy C.; Clark, Chris D.

doi:10.1080/17445647.2015.1010617

Cited by 18 publications

(28 citation statements)

References 44 publications

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“…The mapping is comparable between data sources and independently agrees with available high‐resolution lidar data [ Ely , ]. The map is composed of 42,311 polylines representing LSS segments [ Ely and Clark , ]. LSSs were not mapped across disruptions such as heavily crevassed regions or surface mottling, in order to avoid extrapolation or ambiguity.…”

Section: Methodsmentioning

confidence: 99%

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Insights on the formation of longitudinal surface structures on ice sheets from analysis of their spacing, spatial distribution, and relationship to ice thickness and flow

Ely

Clark

et al. 2017

JGR Earth Surface

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Longitudinal surface structures (LSSs) are prevalent upon the ice streams, ice shelves, and outlet glaciers of ice sheets. These features inform our understanding of past and present ice sheet behavior. However, consensus regarding their genesis has not been reached. Here we analyze 42,311 LSS segments mapped across Antarctica together with geophysical data to determine their morphological and glaciological properties. Most LSSs are spaced 450 to 1500 m apart, a distance positively correlated with the width of the ice flow unit on which they occur. The start points (upstream end locations) of LSSs have diverse ice thicknesses and velocities. The majority of LSSs occur where ice flow is converging or broadly parallel, and they are prominent at ice confluences. Some occur at slow‐flowing ice stream onsets. Occasionally, LSSs relate to sudden variations in basal shear stress due to basal perturbations. From these observations, we argue that LSSs are the consequence of increased strain which occurs during the lateral compression and longitudinal extension of ice: (i) converging/flowing into a channel (this scenario characterizes most LSSs), (ii) at the onset of ice streaming, (iii) at flow unit confluence, and (iv) as ice flows over and around a basal perturbation.

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Section: Methodsmentioning

confidence: 99%

“…(c) Mapped LSSs on glaciers in the Transantarctic Mountains. This mapping is presented in greater detail in Ely and Clark [].…”

Section: Methodsmentioning

confidence: 99%

Insights on the formation of longitudinal surface structures on ice sheets from analysis of their spacing, spatial distribution, and relationship to ice thickness and flow

Ely

Clark

et al. 2017

JGR Earth Surface

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“…Therefore, the geomorphology on the southern foreland is a result of interaction between five narrow ice flow units, which facilitated the delivery of supraglacial, englacial and subglacial debris from nunataks and valley sides and its transportation towards the ice margin along longitudinal flow stripes/foliations (cf. Casassa & Brecher, 1993;Ely & Clark, 2016;Glasser & Gudmundsson, 2012;Hambrey, 1975;Roberson & Hubbard, 2010). One further aspect of the southern foreland is the fact that the five southern ice flow units were squeezed by the two larger northern flow units during the advance of Nordenskiöldbreen, resulting in them advancing relatively further and being compressed and contorted over the site of the present foreland, where they are now melting out.…”

Section: Glacial Landsystemmentioning

confidence: 99%

Glacial geomorphology of the terrestrial margins of the tidewater glacier, Nordenskiöldbreen, Svalbard

2016

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A 1:4000 scale map of the terrestrial margins of the foreland of Nordenskiöldbreen depicts a polythermal glacial landsystem containing a record of the landform signatures of individual ice flow units that operate within the glacier snout. A 1:700 map provides a detailed overview of fluted terrain, based on unmanned aerial vehicle images captured in 2014. The pattern of landforms lying inside the Little Ice Age (LIA) latero-frontal moraine on the northern side of the fjord comprises a fluted till surface, which in turn grades into icemoulded bedrock. This signature records the recession of a single, wide ice flow unit, which was characterised by limited incorporation of subglacial material and restricted delivery of supraglacial debris. Inside the latero-frontal moraine on the south side of the fjord, a fluted surface is subordinate to a pronounced and large ice-cored moraine complex related to the confluence of five narrower ice flow units, each of which transported significant quantities of englacial and supraglacial debris at their suture zones as a series of longitudinal debris stripes. The suite of foreland landforms is diagnostic of both temperate subglacial and frozen-snout conditions, indicating the operation of a warm polythermal glacier fed by multiple flow units during the LIA. ARTICLE HISTORY

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“…A geomorphological map of the foreland of Isfallsglaciären was created in ArcGIS v.10.1 using the exported orthophoto and DEM. The orthophoto was locally contrast‐stretched; a technique which has proven useful for highlighting subtle features on satellite imagery (Ely and Clark, ). The DEM was hill‐shaded from multiple angles (315°, 45° and above) to avoid azimuth biasing, a visualisation technique regularly used for the mapping of subglacial bedforms (Smith and Clark, ; Hillier et al ., ).…”

Section: Methodsmentioning

confidence: 99%

Using UAV acquired photography and structure from motion techniques for studying glacier landforms: application to the glacial flutes at Isfallsglaciären

Ely

Graham

Barr

et al. 2016

Earth Surf Processes Landf

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This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.ABSTRACT: Glacier and ice sheet retreat exposes freshly deglaciated terrain which often contains small-scale fragile geomorphological features which could provide insight into subglacial or submarginal processes. Subaerial exposure results in potentially rapid landscape modification or even disappearance of the minor-relief landforms as wind, weather, water and vegetation impact on the newly exposed surface. Ongoing retreat of many ice masses means there is a growing opportunity to obtain high resolution geospatial data from glacier forelands to aid in the understanding of recent subglacial and submarginal processes. Here we used an unmanned aerial vehicle to capture close-range aerial photography of the foreland of Isfallsglaciären, a small polythermal glacier situated in Swedish Lapland. An orthophoto and a digital elevation model with~2 cm horizontal resolution were created from this photography using structure from motion software. These geospatial data was used to create a geomorphological map of the foreland, documenting moraines, fans, channels and flutes. The unprecedented resolution of the data enabled us to derive morphological metrics (length, width and relief) of the smallest flutes, which is not possible with other data products normally used for glacial landform metrics mapping. The map and flute metrics compare well with previous studies, highlighting the potential of this technique for rapidly documenting glacier foreland geomorphology at an unprecedented scale and resolution. The vast majority of flutes were found to have an associated stoss-side boulder, with the remainder having a likely explanation for boulder absence (burial or erosion). Furthermore, the size of this boulder was found to strongly correlate with the width and relief of the lee-side flute. This is consistent with the lee-side cavity infill model of flute formation. Whether this model is applicable to all flutes, or multiple mechanisms are required, awaits further study.

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Flow-stripes and foliations of the Antarctic ice sheet

Cited by 18 publications

References 44 publications

Insights on the formation of longitudinal surface structures on ice sheets from analysis of their spacing, spatial distribution, and relationship to ice thickness and flow

Insights on the formation of longitudinal surface structures on ice sheets from analysis of their spacing, spatial distribution, and relationship to ice thickness and flow

Glacial geomorphology of the terrestrial margins of the tidewater glacier, Nordenskiöldbreen, Svalbard

Using UAV acquired photography and structure from motion techniques for studying glacier landforms: application to the glacial flutes at Isfallsglaciären

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