Historical analysis and visualization of the retreat of Findelengletscher, Switzerland, 1859–2010

Since the end of the Little Ice Age around 1850, glaciers in Europe have strongly retreated. Thanks to early topographic surveys in Switzerland, accurate maps are available, which enable us to trace glacier changes back in time. The earliest map for all of Switzerland that is usable for a detailed analysis is the Dufour map from around 1850 with subsequent topographic maps on a ~ 20 year interval. Despite the large public and scientific interest in glacier changes through time, this historic dataset has not yet been fully utilized for topographic change assessment or visualization of historic glacier extents. In this study, we use eleven historical topographic maps and more recent digital datasets for the region of Zermatt to analyze geometric changes (length, area and volume) of Findelengletscher as well as for creating animations of glacier evolution through time for use in public communication. All maps were georeferenced, the contour lines digitized, and digital elevation models (DEMs) created and co-registered. Additional digital data like the SRTM X-band DEM and high resolution laser scanning data were used to extend the analysis until 2010. Moreover, one independent DEM from aerial photogrammetry was used for comparison. During the period 1859–2010, Findelengletscher lost 3.5 km of its length (6.9 km in 2010), 4.42 ± 0.13 km² of its area (15.05 ± 0.45 km² in 2010) and 1.32 ± 0.52 km³ of its volume. The average rate of thickness loss is 0.45 ± 0.042 m yr− 1 for the 151 years period. Four periods with high thickness change from − 0.56 m ± 0.28 yr− 1 (1859–1881), − 0.40 ± 0.08 m yr− 1 (1937–1965), − 0.90 ± 0.31 m yr− 1 (1995–2000) and − 1.18 ± 0.02 m yr− 1 (2000–2005) have been identified. Small positive thickness changes were found for the periods 1890–1909 (+ 0.09 ± 0.46 m yr − 1) and 1988–1995 (+ 0.05 ± 0.24 m yr− 1). During its retreat with intermittent periods of advance, the glacier separated into three parts. The above changes are demonstrated through an animation (available from the supplementary material), which has been created to inform the general public

The current deglaciation of the Ortles-Cevedale massif (Eastern Italian Alps): impacts, controls and degree of imbalance.

The Ortles-Cevedale is the largest glacierized mountain group of the Italian Alps hosting 112 ice bodies, with a total area of 76.8 km2. Since the 1980\u2019s, this massif is undergoing a rapid deglaciation, as most of the mountain ranges in the European Alps. The aims of this work were: i) to quantify area and volume change of the Ortles- Cevedale glacier system from the 1980s to the 2000s; ii) to improve the knowledge of factors controlling the spatial variability of the deglaciation; and iii) to assess the degree of imbalance of individual glaciers with respect to the present climate conditions. Two inventories were created, based on Landsat5 TM scenes of 20-09-1987 and 31-08-2009. Contrast-enhanced composites (bands TM5, TM4 and TM3), aerial photos and field surveys (for the most recent period) were used to correct the automatic delineation of glaciers derived from a hard classification based on a threshold applied to a TM3/TM5 ratio image. Since Landsat scenes were acquired at the end of the ablation seasons and fresh snow was absent, the accumulation areas could be roughly determined by mapping the snow covered area. This region was identified from the difference in reflectance between snow and ice in the near infrared band of Landsat (TM4), and mapped after correcting topographic effects to determine surface reflectance. The area-averaged geodetic mass budget was then calculated for the individual glaciers by differencing two Digital Terrain Models (2000s minus 1980s, derived from LiDAR and aerial photogrammetry) and combining the result with the glacier outlines. Afterwards, we examined the mass balance data using statistical analyses (Correlation matrices, Principal Component Analysis, Cluster Analysis). This allowed us highlighting clusters of glaciers, which exhibit a similar behavior, identify the outlayers and the relative influence of the factors controlling spatial variability of the mass losses. Finally, we assessed the degree of imbalance of individual glaciers by comparing the current Accumulation Area Ratios (AAR) with the balanced-budget AAR (AAR0), the latter also accounting for the debris cover of glaciers. We found that the total area loss of the Ortles-Cevedale glaciers from 1987 to 2009 amounts to 23.5 km2, i.e. 23.4% of the initial area. On the other hand, the AAR of the entire glacier system was 0.3 in both investigated years. The overall debris cover increased from 10.5% to 16.3%. The geodetic mass balance rate was -0.7 m w.e. y1(as an average on 112 ice bodies), ranging from -0.1 to -1.7 m w.e. y1. We also found that the main controls of the differing change of single glaciers are related to their hypsometry (elevation range and slope), AAR, feeding source and debris cover. Interestingly, a significant correlation was found between AAR, AAR0 and debris cover. This information was used to assess and visualize the needed additional reduction of individual glaciers to reach equilibrium with the current size of their accumulation areas. This amounts on average to a further reduction of 40% of the current areal extent of glaciers

Neuer Beitrag zur Flora der Insel Mljet

Im vorliegenden Beitrag werden 129 für die Insel Mljet neue Pflanzensippen angegeben. Auf Grund der bisherigen Untersuchungen sind für die Insel insgesammt etwa 500 Gefässpflanzen bekanntgeworden. Die Untersuchungen werden fortgesetzt

Annual to seasonal glacier mass balance in High Mountain Asia derived from Pl\ue9iades stereo images: examples from the Pamir and the Tibetan Plateau

\ua9 Copyright: Glaciers are crucial sources of freshwater in particular for the arid lowlands surrounding High Mountain Asia. To better constrain glacio-hydrological models, annual, or even better, seasonal information about glacier mass changes is highly beneficial. In this study, we evaluate the suitability of very-high-resolution Pl\ue9iades digital elevation models (DEMs) to measure glacier mass balance at annual and seasonal scales in two regions of High Mountain Asia (Muztagh Ata in Eastern Pamirs and parts of western Nyainq\ueantanglha, south-central Tibetan Plateau), where recent estimates have shown contrasting glacier behaviour. The average annual mass balance in Muztagh Ata between 2019 and 2022 was -0.07ĝ€\uaf\ub1ĝ€\uaf0.20ĝ€\uafmĝ€\uafw.e.ĝ€\uafa-1, suggesting the continuation of a recent phase of slight mass loss following a prolonged period of balanced mass budgets previously observed. The mean annual mass balance in western Nyainq\ueantanglha was highly negative for the same period (-0.60ĝ€\uaf\ub1ĝ€\uaf0.15ĝ€\uafmĝ€\uafw.e.ĝ€\uafa-1), suggesting increased mass loss rates compared to the approximately previous 5 decades. The 2022 winter (+0.13ĝ€\uaf\ub1ĝ€\uaf0.24ĝ€\uafmĝ€\uafw.e.) and summer (-0.35ĝ€\uaf\ub1ĝ€\uaf0.15ĝ€\uafmĝ€\uafw.e.) mass budgets in Muztagh Ata and western Nyainq\ueantanglha (-0.03ĝ€\uaf\ub1ĝ€\uaf0.27ĝ€\uafmĝ€\uafw.e. in winter; -0.63ĝ€\uaf\ub1ĝ€\uaf0.07ĝ€\uafmĝ€\uafw.e. in summer) suggest winter- and summer-accumulation-type regimes, respectively. We support our findings by implementing the Sentinel-1-based Glacier Index to identify the firn and wet-snow areas on glaciers and characterize the accumulation type. The good match between the geodetic and Glacier Index results supports the potential of very-high-resolution Pl\ue9iades data to monitor mass balance at short timescales and improves our understanding of glacier accumulation regimes across High Mountain Asia

Error sources and guidelines for quality assessment of glacier area, elevation change, and velocity products derived from satellite data in the Glaciers_cci project

Satellite data provide a large range of information on glacier dynamics and changes. Results are often reported, provided and used without consideration of measurement accuracy (difference to a true value) and precision (variability of independent assessments). Whereas accuracy might be difficult to determine due to the limited availability of appropriate reference data and the complimentary nature of satellite measurements, precision can be obtained from a large range of measures with a variable effort for determination. This study provides a systematic overview on the factors influencing accuracy and precision of glacier area, elevation change (from altimetry and DEM differencing), and velocity products derived from satellite data, along with measures for calculating them. A tiered list of recommendations is provided (sorted for effort from Level 0 to 3) as a guide for analysts to apply what is possible given the datasets used and available to them. The more simple measures to describe product quality (Levels 0 and 1) can often easily be applied and should thus always be reported. Medium efforts (Level 2) require additional work but provide a more realistic assessment of product precision. Real accuracy assessment (Level 3) requires independent and coincidently acquired reference data with high accuracy. However, these are rarely available and their transformation into an unbiased source of information is challenging. This overview is based on the experiences and lessons learned in the ESA project Glaciers_cci rather than a review of the literature

The future sea-level rise contribution of Greenland’s glaciers and ice caps

We calculate the future sea-level rise contribution from the surface mass balance of all of Greenland's glaciers and ice caps (GICs, ~90 000 km2) using a simplified energy balance model which is driven by three future climate scenarios from the regional climate models HIRHAM5, RACMO2 and MAR. Glacier extent and surface elevation are modified during the mass balance model runs according to a glacier retreat parameterization. Mass balance and glacier surface change are both calculated on a 250 m resolution digital elevation model yielding a high level of detail and ensuring that important feedback mechanisms are considered. The mass loss of all GICs by 2098 is calculated to be 2016 ± 129 Gt (HIRHAM5 forcing), 2584 ± 109 Gt (RACMO2) and 3907 ± 108 Gt (MAR). This corresponds to a total contribution to sea-level rise of 5.8 ± 0.4, 7.4 ± 0.3 and 11.2 ± 0.3 mm, respectively. Sensitivity experiments suggest that mass loss could be higher by 20–30% if a strong lowering of the surface albedo were to take place in the future. It is shown that the sea-level rise contribution from the north-easterly regions of Greenland is reduced by increasing precipitation while mass loss in the southern half of Greenland is dominated by steadily decreasing summer mass balances. In addition we observe glaciers in the north-eastern part of Greenland changing their characteristics towards greater activity and mass turnover