Identification and classification of unmapped blanket bogs in the Cordillera Cantábrica, northern Spain

Blanket bogs are rare types of peatland that are recognised internationally for important habitat provision, and nationally and locally as important carbon stores and sinks. These ecosystems enjoy particular attention and protection within the European Union, but gaps highlighted in the Spanish national peatland inventory leave many areas of Spain’s blanket bog habitat unprotected and exposed to anthropogenic pressures such as livestock or wind farm development. This research identifies and offers classification of four currently unmapped areas of blanket bog located in the Cordillera Cantábrica (north Spain) on the administrative boundaries between the regions of Cantabria and Castilla y León. Peat depth was surveyed on a 15 m spaced grid at all sites and mesotope units were defined from topography and hydrological flow patterns. Two sloping and two mound blanket bogs were identified containing a range of bog and fen mesotope units. Maximum peat depth at the five sites ranges from 1.78 to 2.82 m covering an area of 43 ha of blanket bog (> 30 cm peat depth). The survey also estimates that more than 300,000 m³ of peat has accumulated across all sites. This study adds significantly to the known global distribution of blanket mire and suggests that an urgent update of national peatland inventories is needed more widely, not least in Spain, to identify currently unmapped areas of blanket bog. The approach used here can be employed wherever blanket mires occur in the world to promote their designation and the preservation of peatland diversity and carbon storage

The potential of small unmanned aircraft systems and structure-from-motion for topographic surveys: a test of emerging integrated approaches at Cwm Idwal, North Wales

This paper was accepted for publication in the journal Geomorphology and the definitive published version is available at http://dx.doi.org/10.1016/j.geomorph.2014.07.021Novel topographic survey methods that integrate both structure-from-motion (SfM) photogrammetry and small unmanned aircraft systems (sUAS) are a rapidly evolving investigative technique. Due to the diverse range of survey configurations available and the infancy of these new methods, further research is required. Here, the accuracy, precision and potential applications of this approach are investigated. A total of 543 images of the Cwm Idwal moraine–mound complex were captured from a light (b5 kg) semi-autonomous multi-rotor unmanned aircraft system using a consumer-grade 18 MP compact digital camera. The imageswere used to produce a DSM(digital surfacemodel) of themoraines. The DSMis in good agreement with 7761 total station survey points providing a total verticalRMSE value of 0.517mand verticalRMSE values as lowas 0.200mfor less densely vegetated areas of the DSM. High-precision topographic data can be acquired rapidly using this technique with the resulting DSMs and orthorectified aerial imagery at sub-decimetre resolutions. Positional errors on the total station dataset, vegetation and steep terrain are identified as the causes of vertical disagreement. Whilst this aerial survey approach is advocated for use in a range of geomorphological settings, care must be taken to ensure that adequate ground control is applied to give a high degree of accuracy

Reconstruction of former glacier surface topography from archive oblique aerial images

Archive oblique aerial imagery offers the potential to reconstruct the former geometry of valley glaciers and other landscape surfaces. Whilst the use of Structure-from-Motion (SfM) photogrammetry with multiview stereopsis (MVS) to process small-format imagery is now well established in the geosciences, the potential of the technique for extracting topographic data from archive oblique aerial imagery is unclear. Here, SfM-MVS is used to reconstruct the former topography of two high-Arctic glaciers (Midtre and Austre Lovénbreen, Svalbard, Norway) using three archive oblique aerial images obtained by the Norwegian Polar Institute in 1936. The 1936 point cloud was produced using seven LiDAR-derived ground control points located on stable surfaces in proximity to the former piedmont glacier termini. To assess accuracy, the 1936 data set was compared to a LiDAR data set using the M3C2 algorithm to calculate cloud-to-cloud differences. For stable areas (such as nonglacial surfaces), vertical differences were detected between the two point clouds (RMS M3C2 vertical difference of 8.5 m), with the outwash zones adjacent to the assessed glacier termini showing less extensive vertical discrepancies (94% of M3C2 vertical differences between ±5 m). This research highlights that historical glacier surface topography can be extracted from archive oblique aerial imagery, but accuracy is limited by issues including the lack of camera calibration, the quality and resolution of the archive imagery, and by the identification of suitable ground control. To demonstrate the value of historical glacier surfaces produced using oblique archive imagery, the reconstructed glacier surface topography is used to investigate evidence of a potential former surge front at the high-Arctic valley glacier, Austre Lovénbreen - a glacier identified to have potentially exhibited surge-type behaviour during the Neoglacial. A surface bulge of ~15–20 m is resolved on the 1936 model; however, when compared with the now deglaciated former subglacial topography, a surge origin for the surface feature becomes unclear. The processed 1936 oblique imagery was also used to produce orthorectified nadir aerial imagery, from which structural mapping was undertaken: this adds to the existing 1948–1995 structural map series for these glaciers. This research demonstrates the potential of SfM-MVS for reconstructing historical glacier surfaces, which is important for aiding our understanding of former glacier dynamics and enabling the rapid assessment of glacier change over time

Ice-cored moraine degradation mapped and quantified using an unmanned aerial vehicle: a case study from a polythermal glacier in Svalbard

Ice-cored lateral–frontal moraines are common at the margins of receding high-Arctic valley glaciers, but the preservation potential of these features within the landform record is unclear. Recent climatic amelioration provides an opportunity to study the morphological evolution of these landforms as they de-ice. This is important because high-Arctic glacial landsystems have been used as analogues for formerly glaciated areas in the mid-latitudes. This study uses SfM (Structure-from-Motion) photogrammetry and a combination of archive aerial and UAV (unmanned aerial vehicle) derived imagery to investigate the degradation of an ice-cored lateral–frontal moraine at Austre Lovénbreen, Svalbard. Across the study area as a whole, over an 11-year period, the average depth of surface lowering was − 1.75 ± 0.89 m. The frontal sections of the moraine showed low or undetectable rates of change. Spatially variable rates of surface lowering are associated with differences in the quantity of buried ice within the structure of the moraine. Morphological change was dominated by surface lowering, with limited field evidence of degradation via back-wastage. This permits the moraine a greater degree of stability than previously observed at other sites in Svalbard. It is unclear whether the end point will be a fully stabilised ice-cored moraine, in equilibrium with its environment, or an ice-free lateral–frontal moraine complex. Controls on geomorphological change (e.g. topography and climate) and the preservation potential of the lateral–frontal moraine are discussed. The methods used by this research also demonstrate the potential value of SfM photogrammetry and unmanned aerial vehicles for monitoring environmental change and are likely to have wider applications in other geoscientific sub-disciplines

Sedimentary and tectonic architecture of a large push moraine : a case study from Hagafellsjökull-Eystri, Iceland

Original article can be found at: http://www.sciencedirect.com/science/journal/00370738 Copyright Elsevier B.V. [Full text of this article is not available in the UHRA]Using a combination of geological and geophysical techniques (Ground Penetrating Radar), we explore the tectonic architecture of a push moraine formed just after the 1890 Neoglacial ice maximum of Hagafellsjökull-Eystri, in central Iceland. The push moraine formed by a re-advance, perhaps a surge, of the glacier against a moraine bank-delta sometime between 1890 and 1929. Different tectonic architectures exist in two adjacent parts of the same push moraine complex. In one location, the ice advance pushed the delta pro-glacially to form a prominent single-crested push moraine. Deformation occurred along a single listric décollement over which a large nappe moved, as a result of ice-marginal pushing. In an adjacent location, the ice-margin mounted and advanced over the ice-contact delta to create a push moraine at the limit of the advance by subglacial gravity-spreading. In this case, deformation occurred along a series of listric thrusts and by folding within the distal parts of the over-ridden delta. The geomechanical causes of these two contrasting styles of deformation, present in adjacent sectors of the same ice-marginal flow unit, are discussed and a range of possible controls identified. These include variation along the former ice-margin and foreland in: (1) glacier–foreland coupling; (2) foreland shear strength; and (3) the frictional characteristics of the décollement. Some combination of these variables provides the most likely cause. The case study presented in this paper provides an example of the potential for rapid variation in the tectonic architecture of a push moraine along strike.Peer reviewe

Terminal zone glacial sediment transfer at a temperate overdeepened glacier system

Continuity of sediment transfer through glacial systems is essential to maintain subglacial bedrock erosion, yet transfer at temperate glaciers with overdeepened beds, where subglacial fluvial sediment transport should be greatly limited by adverse slopes, remains poorly understood. Complex multiple transfer processes in temperate overdeepened systems has been indicated by the presence of large frontal moraine systems, supraglacial debris of mixed transport origin, thick basal ice sequences, and englacial thrusts and eskers. At Svínafellsjökull, thrusts comprising decimetre-thick debris-rich bands of stratified facies ice of basal origin, with a coarser size distribution and higher clast content than that observed in basal ice layers, contribute substantially to the transfer of subglacial material in the terminal zone. Entrainment and transfer of material occurs by simple shear along the upper surface of bands and by strain-induced deformation of stratified and firnified glacier ice below. Thrust material includes rounded and well-rounded clasts that are also striated, indicating that fluvial bedload is deposited as subglacial channels approach the overdeepening and then entrained along thrusts. Substantial transfer also occurs within basal ice, with facies type and debris content dependent on the hydrological connectedness of the adverse slope. A process model of transfer at glaciers with terminal overdeepenings is proposed, in which the geometry of the overdeepening influences spatial patterns of ice deformation, hydrology, and basal ice formation. We conclude that the significance of thrusting in maintaining sediment transfer continuity has likely been overlooked by glacier sediment budgets and glacial landscape evolution studies