Calibrated ice thickness estimate for all glaciers in Austria

Knowledge on ice thickness distribution and total ice volume is a prerequisite for computing future glacier change for both glaciological and hydrological applications. Various ice thickness estimation methods have been developed but regional differences in fundamental model parameters are substantial. Parameters calibrated with measured data at specific points in time and space can vary when glacier geometry and dynamics change. This study contributes to a better understanding of accuracies and limitations of modeled ice thicknesses by taking advantage of a comprehensive data set of in-situ ice thickness measurements from 58 glaciers in the Austrian Alps and observed glacier geometries of three Austrian glacier inventories (GI) between 1969 and 2006. The field data are used to calibrate an established ice thickness model to calculate an improved ice thickness data set for the Austrian Alps. A cross-validation between modeled and measured point ice thickness indicates a model uncertainty of 25–31% of the measured point ice thickness. The comparison of the modeled and measured average glacier ice thickness revealed an underestimation of 5% with a mean standard deviation of 15% for the glaciers with calibration data. The apparent mass balance gradient, the primary model parameter accounting for the effects of surface mass balance distribution as well as ice flux, substantially decreases over time and has to be adjusted for each temporal increment to correctly reproduce observed ice thickness. This reflects the general stagnation of glaciers in Austria. Using the calibrated parameter set, 93% of the observed ice thickness change on a glacier-specific scale could be captured for the periods between the GI. We applied optimized apparent mass balance gradients to all glaciers of the latest Austrian glacier inventory and found a volume of 15.9 km3 for the year 2006. The ten largest glaciers account for 25% of area and 35% of total ice volume. An estimate based on mass balance measurements from nine glaciers indicates an additional volume loss of 3.5 ± 0.4 km3 (i.e., 22 ± 2.5%) until 2016. Relative changes in area and volume were largest at glaciers smaller than 1 km2, and relative volume changes appear to be higher than relative area changes for all considered time periods

Twenty-three unsolved problems in hydrology (UPH) – a community perspective

This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through on-line media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focussed on process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come

Ice thickness distribution and glacier bed of Hallstätter Gletscher

Hallstätter Glacier is the northernmost glacier of Austria. Appendant to the northern Limestone Alps, the glacier is located at 47°28'50'' N, 13°36'50'' E in the Dachstein-region. At the same time with its advance linked to the Little Ice Age (LIA), research on changes in size and mass of Hallstätter glacier was started in 1842 by Friedrich Simony. He observed and documented the glacier retreat related to its last maximum extension in 1856. In addition, Hallstätter Glacier is a subject to scientific research to date. In this thesis methods and results of ongoing mass balance measurements are presented and compared to long term volume changes and meteorological observations. The current mass balance monitoring programm using the direct glaciological method was started 2006. In this context, 2009 the ice thickness was measured with ground penetrating radar. The result are used with digital elevation models reconstucted from historical maps and recent digital elevation models to calculate changes in shape and volume of Hallstätter Glacier. Based on current meteorological measurements near the glacier and longtime homogenized climate data provided by HISTALP, time series of precipitation and temperature beginning at the LIA are produced. These monthly precipitation and monthly mean temperature data are used to compare results of a simple degree day model with the volume change calculated from the difference of the digital elevation models. The two years of direct mass balance measurements are used to calibrate the degree day model. A number of possible future scenarios are produced to indicate prospective changes. Within the 150-year-period between 1856 and 2007 the Hallstätter Glacier lost 1940 meters of its length and 2.23 km**2 in area. 37% of the initial volume of 1856 remained. This retreat came along with a change in climate. The application of a running avarage of 30 years shows an increase in precipitation of 18.5% and a warming of 1.3°C near the glacier between 1866 and 1993. The mass loss was continued in the hydrological years 2006/2007 and 2007/2008 showing mean specific mass balance of -376 mm and -700 mm, respectively. Applying a temperature correction for the different minimum elevations of the glacier, the degree day approach based on the two measured mass balances can reproduce sign and order of magnitude of the volume change of Hallstätter Glacier since 1856. Nevertheless, the relative deviation is significant. Future scenarios show, that 30% of the entire glacier volume remains after subtracting the elevation changes between the digital elevation models of 2002 and 2007 ten times from the surface of 2007. The past and present mass changes of Hallstätter Glacier are showing a retreating glacier as a consequence of rising temperatures. Due to high precepitation, increased with previous warming, the Hallstätter Glacier can and will exist in lower elevation compared to inner alpine glaciers

Analysis of the spatial and temporal variation of seasonal snow accumulation in alpine catchments using airborne laser scanning : basic research for the adaptation of spatially distributed hydrological models to mountain regions

Die Kenntnis der räumlichen Verteilung der Schneedecke im Hochgebirge ist eine Voraussetzung für die realistische Modellierung des Abflussgeschehens alpiner Einzugsgebiete. Diese Studie präsentiert die Anwendung von luftgestützten Laserscanning Daten (Airborne Laser Scanning, ALS) zur Bestimmung der räumlichen Schneedeckenverteilung im eisfreien und vergletscherten Terrain. Die mit Hilfe von ALS gemessenen Oberflächenänderungen wurden mit den von Bodenradarmessungen berechneten Schneehöhen verglichen. Aufgrund der geringen Firnbedeckung und den in den letzten Jahrzehnten reduzierten Eisbewegungen in den untersuchten Gebieten sind die Abweichungen auf einem Großteil der Gletscherflächen gering. 75% der Gesamtfläche zeigten eine geringe zeitliche Variabilität der standardisierten Schneehöhen. Ein großer Teil der Flächen mit zeitlich hoher Variabilität der Schneehöhen ist in Gebieten zu finden, in denen sich die Eisbedeckung in dem10-jährigen Untersuchungszeitraum geändert hat. Lawinen und Schneerutsche tragen einen stetigen Teil zur Akkumulation auf Gletschern bei, dessen zusätzliches Volumen allerdings gering ist. Mit Hilfe der ALS Daten konnte nicht nur die Abflusssimulation verbessert werden, sondern auch die Simulation der Schneedeckenverteilung im Hochgebirge und des Massenhaushaltes der Gletscher. Die Ergebnisse zeigen, dass ALS Daten eine nützliche Quelle für die ausgiebige Analyse von Mustern der Schneebedeckung und für die Abflussmodellierung im Hochgebirge darstellen.Information about the spatial distribution of snow accumulation is a prerequisitefor adaptating hydro-meteorological models to achieve realistic simulations of therunoff from mountain catchments. Therefore, the spatial snow depthdistribution in complex topography of ice-free terrain and glaciers was investigatedusing airborne laser scanning (ALS) data. This thesis presents for the first timean analysis of the persistence and the variability of the snow patterns at the endof five accumulation seasons in a comparatively large catchment. ALS derived seasonal surface elevation changes on glaciers were compared to the actual snow depths calculated from ground penetrating radar (GPR) measurements. Areas of increased deviations. In the investigated region, the ALS-derived snow depths on most of the glacier surface do not deviate markedly from actual snow depths. 75% of a the total area showed low inter-annual variability of standardized snow depthsat the end of the five accumulation seasons. The high inter-annual variability of snow depths could be attributed to changes in the ice cover within the investigated 10-yearperiod for much of the remaining area. Avalanches and snow sloughs continuously contribute to the accumulation on glaciers, but their share of the total snow covervolume is small. The assimilation of SWE maps calculated from ALS data in the adaptation of snow-hydrological models to mountain catchments improved the results not only for the but also for the simulated snow cover distribution and for the mass balance of the glaciers. The results demonstrate that ALS data are a beneficial source for extensive analysis of snow patterns and for modeling the runoff from high Alpine catchments.by Kay HelfrichtAbweichender Titel laut Übersetzung der Verfasserin/des VerfassersEnth. u.a. 3 Veröff. d. Verf. aus den Jahren 2012 - 2014 . - Zsfassung in dt. SpracheInnsbruck, Univ., Diss., 2014OeBB(VLID)15315

Einfluss des Klimawandels auf die Schneebedeckung

Die Schneebedeckung ist ein entscheidender Parameter für den Energiehaushalt der Erde, da Schneeoberflächen einen großen Teil der einfallenden Globalstrahlung reflektieren. Die Ausprägung der Schneedecke hängt dabei besonders stark von der Temperatur während des Niederschlages und darüber hinaus von der Niederschlagsmenge sowie den Witterungsbedingungen vor und nach einem Schneefallereignis ab. Mit dem Temperaturanstieg über die vergangenen Jahrzehnte wurde global eine Abnahme der Schneebedeckung vor allem in sehr temperatursensitiven Höhenlagen um den Bereich der Schneefallgrenze beobachtet. Signifikante Langfristtrends in der Schneedeckendauer sowie der Schneehöhe sind in den meisten Gebirgen der Welt zu finden, auch wenn diese von einer großen natürlichen Variabilität der Schneebedeckung von Jahr zu Jahr sowie dekadischen Schwankungen überlagert sind. Climate change impacts on snow cover: The snow cover is an important parameter in the energy balance of the Earth, since snow surfaces reflect a large part of the incident global radiation. The state of the snow cover is particularly dependent on the temperature during precipitation events, but also on the amount of precipitation and the prevailing weather conditions before and after a snowfall. As a consequence of rising temperatures over the past decades, a decrease in snow cover has been observed worldwide, especially at very temperature-sensitive altitudes around the snow line. Significant long-term trends in snow cover duration and snow depth can be found in most mountain regions of the world. These trends are overlaid by a high natural year-to-year and decadal variability