Recent changes in glacier area in the Central Southern Alps of New Zealand : - Mapped from ASTER satellite imagery

Change in glacier extent is a good indication of climate change. Inventories for glaciated areas should therefore be made at certain intervals. For New Zealand a digitized glacial inventory including both the two main islands’ glaciers was made from aerial photographs recorded in 1978. This inventory needed an update. One Aster scene (60*60km) recorded 14. February 2002 covering the central Southern Alps of New Zealand is used for the updating. The area covered by the image contained, in 1978, 41% of the glaciated areas in New Zealand. The image was orthorectified using a combination of points collected in field and points from the New Zealand topographic database and DEM made from 20-meter contour intervals in PCI. Due to the problems often involved in automatic methods for glacier extraction, the glacier areas on the image were manually digitized. For validation of the digitizing, field work was conducted during late summer of 2005 (Feb-April). Glacier outlines were mapped for 9 individual glaciers using a differential GPS. These data were later corrected to a base antenna giving sub-meter accuracy. 5 of these 9 glaciers were so called ‘Index glaciers’ that had been annually photographed since 1977 as a part of the New Zealand Annual Snowline Survey. Aerial photographs of the 5 field work Index glaciers, were used to adjust for eventual changes in the glacier outlines between image acquisition and the in-situ recordings. Automatic classifications were tested on the entire image and on 3 zoomed in study areas to give an estimate of the efficiency of these automatic methods in the New Zealand setting. Band ratio of ATER3/ASTER4 proved to be the most efficient automatic classification method, with the threshold set around 2.0. However, as a result of the large debris cover on many glaciers in New Zealand, automatic glacier extraction would require significant manual post processing. The manually digitized glacier map was used to calculate the change in glacier area since 1978. An overall reduction of 16.6% was found, more specifically 14.3% for the western and 18.3% eastern side of the Main Divide of the Southern Alps. The large and fast flowing western glaciers, Fox and Franz Josef Glaciers, were pulsing back and forward in the study period, but showed an overall advance, whereas the large low-gradient heavily debris covered valley glaciers developed proglacial lakes and have shown a rapidly increasing retreat due to calving. The smaller high elevated alpine glaciers in the area show only slight changes

Analysis of filtering techniques for investigating landslide-induced topographic changes in the Oetz Valley (Tyrol, Austria)

Landslides endanger settlements and infrastructure in mountain areas across the world. Monitoring of landslides is therefore essential in order to understand and possibly predict their behavior and potential danger. Terrestrial laser scanning has proven to be a successful tool in the assessment of changes on landslide surfaces due to its high resolution and accuracy. However, it is necessary to classify the 3D point clouds into vegetation and bare-earth points using filtering algorithms so that changes caused by landslide activity can be quantified. For this study, three classification algorithms are compared on an exemplary landslide study site in the Oetz valley in Tyrol, Austria. An optimal set of parameters is derived for each algorithm and their performances are evaluated using different metrics. The volume changes on the study site between the years 2017 and 2019 are compared after the application of each algorithm. The results show that (i) the tested filter techniques perform differently, (ii) their performance depends on their parameterization and (iii) the best-performing parameterization found over the vegetated test area will yield misclassifications on non-vegetated rough terrain. In particular, if only small changes have occurred the choice of the filtering technique and its parameterization play an important role in estimating volume changes.publishedVersio

Late Weichselian local ice dome configuration and chronology in Northwestern Svalbard: early thinning, late retreat

The chronology and configuration of the Svalbard Barents Sea Ice Sheet (SBSIS) during the Late Weichselian (LW) are based on few and geographically scattered data. Thus, the timing and configuration of the SBSIS has been a subject of extensive debate. We present provenance data of erratic boulders and cosmogenic 10Be ages of bedrock and boulders from Northwest Spitsbergen (NWS), Svalbard to determine the thickness, configuration and chronology during the LW. We sampled bedrock and boulders of mountain summits and summit slopes, along with erratic boulders from coastal locations around NWS. We suggest that a local ice dome over central NWS during LW drained radially in all directions. Provenance data from erratic boulders from northern coastal lowland Reinsdyrflya suggest northeastward ice flow through Liefdefjorden. 10Be ages of high-elevation erratic boulders in central NWS (687–836 m above sea level) ranging from 18.3 ± 1.3 ka to 21.7 ± 1.4 ka, indicate that the centre of a local ice dome was at least 300 m thicker than at present. 10Be ages of all high-elevation erratics (>400 m above sea level, central and coastal locations) indicate the onset of ice dome thinning at 25–20 ka. 10Be ages from erratic boulders on Reinsdyrflya ranging from 11.1 ± 0.8 ka to 21.4 ± 1.7 ka, indicate an ice cover over the entire Reinsdyrflya during LW and a complete deglaciation prior to the Holocene, but apparently later than the thinning in the mountains. Lack of moraine deposits, but the preservation of beach terraces, suggest that the ice covering this peninsula possibly was cold-based and that Reinsdyrflya was part of an inter ice-stream area covered by slow-flowing ice, as opposed to the adjacent fjord, which possibly was filled by a fast-flowing ice stream. Despite the early thinning of the ice sheet (25–20 ka) we find a later timing of deglaciation of the fjords and the distal lowlands. Several bedrock samples (10Be) from vertical transects in the central mountains of NWS pre-date the LW, and suggest either ice free or pervasive cold-based ice conditions. Our reconstruction is aligned with the previously suggested hypothesis that a complex multi-dome ice-sheet-configuration occupied Svalbard and the Barents Sea during LW, with numerous drainage basins feeding fast ice streams, separated by slow flowing, possibly cold-based, inter ice-stream areas

Minimal erosion of Arctic alpine topography during late Quaternary glaciation

The alpine topography observed in manymountainous regions is thought to have formed during repeated glaciations of the Quaternary period1,2. Before this time, landscapes had much less relief1–3. However, the spatial patterns and rates of Quaternary exhumation at high latitudes—where cold-based glaciers may protect rather than erode landscapes—are not fully quantified. Here we determine the exposure and burial histories of rock samples from eight summits of steep alpine peaks in northwestern Svalbard (79.5 ◦ N) using analyses of 10Be and 26Al concentrations4,5. We find that the summits have been preserved for at least the past one million years. The antiquity of Svalbard’s alpine landscape is supported by the preservation of sediments older than one million years along a fjord valley6, which suggests that both mountain summits and low-elevation landscapes experienced very lo