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The high-altitudinal plateaus of Jotunheimen in central South Norway, the mountain region home of Norway's highest summits, create a unique and diverse natural environment. The specific gross morphology of Jotunheimen facilitates the occurrence of a variety of periglacial landforms ranging considerably in both dimension and age. The regional distribution of permafrost is one of the major controlling factors for the altitudinal distribution of these periglacial landforms. The largest individual features of patterned ground, undisputed the regionally most dominant periglacial landforms, are situated on terrain currently underlain by permafrost. They visually appear to be quite relict, despite the occurrence of permafrost, and the exact timing of their formation remains unknown. This example points to additional factors significantly influencing the periglacial landform assemblage, like topography, ground moisture availability, and the local deglaciation history. The lack of a regional overview regarding periglacial landforms in Jotunheimen exacerbates the need for a profound investigation of their altitudinal zonation and potential causal links to climate, permafrost, (de-)glaciation, and other factors.The compilation of a regional overview based on aerial imagery and a literature review aims, therefore, to reveal further insight into the controlling factors for and mechanisms of periglacial landform development in Jotunheimen. This shall be achieved by creating an altitudinal zonation for periglacial features and highlighting causal links between their spatial/altitudinal distribution and possible influencing factors. In an outlook to future studies this attempt may also provide more detailed information on the regional basal properties of the former Scandinavian ice sheet, the regional/local deglaciation patterns for the Jotunheimen region, and about the exact chronology of formation of the periglacial landforms studied. [ABSTRACT FROM AUTHOR]

Feedbacks between geomorphic and vegetation dynamics create spatial patterns of vegetation, soils and landforms in biogeomorphic ecosystems and determine their structure and functioning. In glacier forelands, it was shown that these biogeomorphic feedbacks link paraglacial adjustment and vegetation succession and control landscape development and stability over space and time (Eichel et al. 2016, 2018). However, the role of biogeomorphic feedbacks also depends on the environmental setting of the biogeomorphic ecosystem, e.g. on its geomorphic disturbance regime and the occurrence of ecosystem engineer species. In glacier forelands, previous research has primarily focussed on the European Alps and different environmental settings have not been comprehensively investigated yet. Here, we explore the coupling between paraglacial adjustment and vegetation succession in the Southern Alps, New Zealand. In comparison to previously investigated glacier forelands in the European Alps, the selected foreland of Mueller Glacier is characterized by an extraordinarily high geomorphic activity due to high amounts of precipitation (~4000 mm yr-1) and frequent storm events, a mostly continuous glacier wastage since the Little Ice Age maximum (1730/1735) and a mostly endemic flora. Our objectives are to (i) analyse linkages between paraglacial adjustment and vegetation succession in space and time, (ii) identify potential ecosystem engineer species, and (iii) determine the extent of biogeomorphic feedbacks and their role for landscape development and stability. To assess biogeomorphic feedbacks in space and time, we conducted a vegetation and environmental plot survey (55 plots) and created geomorphic and vegetation maps from field mapping, a UAV survey and deep learning algorithms (convolutional neural networks). Finally, we linked geomorphic and ecologic properties to the glacial chronology (Winkler, 2018). Analyses of plot data, geomorphic and vegetation maps show that (i) paraglacial adjustment and vegetation succession are mostly independent from terrain age but depend on material properties and are interlinked in a biogeomorphic succession. (ii) Once geomorphic activity decreases, stable patches are created by the prostate/low growing shrub species Muehlenbeckia axillaris and Coriaria spp., which are therefore potential ecosystem engineer species that promote slope stabilization and facilitate further vegetation succession. (iii) Biogeomorphic feedbacks mostly occur on a local (patch) scale, large areas of the foreland are either dominated by unvegetated highly active slopes or dense late-successional vegetation. Yet, our results indicate that vegetation colonization and ecosystem engineering are important controls for landscape stabilization, which can take substantially longer than in the European Alps. In conclusion, our study shows that similar biogeomorphic feedbacks link paraglacial adjustment and vegetation succession in the European and the Southern Alps, but feedback strength and extent depend on environmental setting.ReferencesEichel J, Corenblit D, Dikau R (2016) Conditions for feedbacks between geomorphic and vegetation dynamics on lateral moraine slopes: a biogeomorphic feedback window. Earth Surf Process Landforms 41:406–419. doi:10.1002/esp.3859Eichel J, Draebing D, Meyer N (2018) From active to stable: paraglacial transition of Alpine lateral moraine slopes. Land Degradation & Development 29:4158–4172. doi:10.1002/ldr.3140Winkler S (2018) Investigating Holocene mountain glaciations: a plea for the supremacy of glacial geomorphology when reconstructing glacier chronologies. Erdkunde 72:215–234. doi:10.3112/erdkunde.2018.03.04 [ABSTRACT FROM AUTHOR]

Research on mountain glaciations has a long history and in the light of current global change, they are increasingly recognised as highly important palaeoclimatic archives for the immediate and more distant geological past. One of the most important leaps forward with the investigation of mountain glaciations during the past 2 decades was substantial improvement achieved within the field of numerical age dating techniques, in particular progress of surface exposure dating using cosmogenic radionuclides (CRN). This development has definitely given the entire research field new momentum. Unfortunately, this methodological progress is in many cases not matched by the recommended necessary level of precautions regarding the interpretative steps with the reconstruction of Holocene glacier chronologies. Improved precision and accuracy with numerical dating techniques comes often with an increasing lack of attention with the geomorphological analysis of the dated landforms. With recent studies it has subsequently become more popular to outline moraines primarily based on individual CRN boulder age clusters without detailed geomorphological mapping or examination. Such an attempt has also been conducted on Holocene glacier forelands in Aoraki/Mt.Cook National Park where a substantial number of CRN boulders ages have been employed to identify and label numerous "moraines". Subsequently, arithmetic means of CRN ages for these apparent "moraines" were linked to individual glacier advances and palaeoclimatically interpreted accordingly. A sound geomorphological analysis of the studied glacier foreland does, however, reveal that this procedure is actually erroneous. Among the problems identified are (a) inclusion of hugely overprinted moraine remnants that lack proper characterisation, (b) wrong subdivision of moraine segments belonging to one defined individual moraines, and (c) mismatching of apparent CRN ages for moraine segments that morphologically need to correspond for any meaningful reconstruction of former marginal positions. A revision of this particular glacier chronology provides major implications for any subsequent palaeoclimatic interpretation as the number of reliably documented neoglacial events decrease from 9 to 5.The value of geomorphological analysis in the context of investigating mountain glaciations is, however, not primarily restricted to chronological approaches. It may also provide assistance with the conceptual context for mechanisms of deglaciation patterns or long-term landscape evolution. In the upper Waimakariri River catchment following a Late Glacial readvance dated to c. 17.5 ka ago, a lake dammed by the related moraine system and debris-covered dead ice should have existed for many centuries before it subsequently drained. That lake would naturally have influenced both the immediate deglaciation mechanism and landform evolution post-LGM. Despite introduced during the 1950s, the concept of this particular palaeo-lake has never been exposed to any detailed geomorphological analysis yet. Whereas the existence of a post-LGM palaeo-lake itself remains out of question, the proposed link to glacier retreat following a Late Glacial re-advance is unrealistic in light of a logical time sequence for individual elements of the local landform assemblage. The lake needs to be younger and postdate Deglaciation in this section of the Waimakariri River.Summarising, detailed geomorphological analysis is indispensable with any attempt to investigate mountain glaciations. [ABSTRACT FROM AUTHOR]

Growth and decay of Quaternary glaciers and ice sheets had fundamental implications for environmental changes worldwide. The chronology of the last deglaciation following the Last Glacial Maximum (LGM, 26.5-20 ka) and its ice marginal positions in Norway are generally perceived as being well constrained. The detailed vertical extent in Norway remains, however, still uncertain over large areas. The knowledge of the vertical dimension of the LGM ice sheet can provide crucial information on palaeo-environmental factors like sea-level changes, atmospheric and oceanic circulation, (de-)glaciation patterns, which are important variables for climate modelling. The interpretation of differently weathered bedrock in mountain areas affected by Quaternary glaciation can be crucial for determining ice-sheet behaviour and thickness. Based on 10Be terrestrial cosmogenic nuclide dating and Schmidt-hammer exposure age-dating (SHD) performed in eastern and western South Norway, we provide new insights in (de)glaciation patterns, landform evolution and estimate ice thickness during and following the LGM. We present the first numerical dates from the western study area showing that deglaciation started ~4 ka earlier and ice sheet downwasting lasted longer than assumed. SHD ages obtained from periglacial and related landforms (e.g. rock-slope failures, pronival ramparts) in this area point to their stabilization during the Holocene Thermal Maximum (~8-5 ka). The rock-slope failures investigated did not occur shortly after local deglaciation, it appears that they cluster around warm periods due to climate-driven factors, like decreasing permafrost depth or increasing cleft-water pressure. Exposed bedrock at the summit in the eastern study area yields a 10Be exposure age predating the Late Weichselian Maximum of 43.7 ± 1.9 ka, possibly indicating ice free areas during the LGM. Instead of the inferred ice coverage at ~15 ka, our SHD ages from blockfields suggest ice-free and severe periglacial conditions occurred earlier. Landforms above 1450 m a.s.l. (e.g. sorted stone polygons, blockstreams) do not show any form of reactivation during cold periods within the Late Glacial or the Holocene. Our results have wider implications on the glaciation history of the area. The results point to a more complex ice sheet behaviour than previously expected. Therefore, we suggest a more complex and topographically controlled configuration of the LGM ice sheet in relation to previous reconstructions. [ABSTRACT FROM AUTHOR]

Ground-based whole sky cameras are now-a-days extensively used for localized monitoring of the clouds. They capture hemispherical images of the sky at regular intervals using a fisheye lens. In this paper, we derive a model for estimating the solar irradiance using pictures taken by those imagers. Unlike pyranometers, these sky images contain information about the cloud coverage and can be used to derive cloud movement. An accurate estimation of the solar irradiance using solely those images is thus a first step towards short-term solar energy generation forecasting, as cloud movement can also be derived from them. We derive and validate our model using pyranometers co-located with our whole sky imagers. We achieve a root mean square error of 178 Watt/m² between estimated and measured solar irradiance, outperforming state-of-the-art methods using other weather instruments. Our method shows a significant improvement in estimating strong short-term variations. [ABSTRACT FROM AUTHOR]

Sky-cloud images obtained from ground-based sky cameras are usually captured using a fisheye lens with a wide field of view. However, the sky exhibits a large dynamic range in terms of luminance, more than a conventional camera can capture. It is thus difficult to capture the details of an entire scene with a regular camera in a single shot. In most cases, the circumsolar region is overexposed, and the regions near the horizon are underexposed. This renders cloud segmentation for such images difficult. In this paper, we propose HDRCloudSeg - an effective method for cloud segmentation using high-dynamic-range (HDR) imaging based on multiexposure fusion. We describe the HDR image generation process and release a new database to the community for benchmarking. Our proposed approach is the first using HDR radiance maps for cloud segmentation and achieves very good results. [ABSTRACT FROM AUTHOR]

Sky/cloud images obtained from ground-based sky-cameras are usually captured using a fish-eye lens with a wide field of view. However, the sky exhibits a large dynamic range in terms of luminance, more than a conventional camera can capture. It is thus difficult to capture the details of an entire scene with a regular camera in a single shot. In most cases, the circumsolar region is over-exposed, and the regions near the horizon are under-exposed. This renders cloud segmentation for such images difficult. In this paper, we propose HDRSeg - an effective method for cloud segmentation using High-Dynamic-Range (HDR) imaging based on multi-exposure fusion. We describe the HDR generation process and release a new database to the community for benchmarking. Our proposed approach is the first using HDR images for cloud segmentation and achieves very good results. [ABSTRACT FROM AUTHOR]