ALBERT

Description: Surface digital elevation models (DEMs) and slope-related estimates of glacier thickness enable modelling of glacier-bed topographies over large ice-covered areas. Due to the erosive power of glaciers, such bed topographies can contain numerous overdeepenings, which when exposed following glacier retreat may fill with water and form new lakes. In this study, the bed overdeepenings for similar to 28 000 glaciers (40 775 km(2)) of the Himalaya-Karakoram region are modelled using GlabTop2 (Glacier Bed Topography model version 2), in which ice thickness is inferred from surface slope by parameterizing basal shear stress as a function of elevation range for each glacier. The modelled ice thicknesses are uncertain (+/- 30%), but spatial patterns of ice thickness and bed elevation primarily depend on surface slopes as derived from the DEM and, hence, are more robust. About 16 000 overdeepenings larger than 104 m(2) were detected in the modelled glacier beds, covering an area of similar to 2200 km(2) and having a volume of similar to 120 km(3) (3-4% of present-day glacier volume). About 5000 of these overdeepenings (1800 km(2)) have a volume larger than 10(6) m(3). The results presented here are useful for anticipating landscape evolution and potential future lake formation with associated opportunities (tourism, hydropower) and risks (lake outbursts).

Description: SUMMARYThe current situation of volatile milk prices and rising costs of, e.g. grain and labour, suggests that it is worth studying productivity and efficiency in dairy farming. The objective of the current whole-system study, carried out in lowland Central Switzerland from 2007 to 2010, was to compare the performance, efficiency, land productivity and profitability of indoor-feeding (IF) dairy production with that of pasture-based feeding (PF) dairy production. An IF herd consisting of 11 Holstein–Friesian (HF) and 13 Brown Swiss (BS) cows was kept in a free-stall barn and fed a part-mixed ration (PMR) of maize silage, grass silage and protein concentrate. The cows were allocated 15·8 ha of agricultural land (AL). In the PMR, an average per lactation of 443 kg protein concentrate and 651 kg compound feed was fed by a concentrate dispenser according to the requirements of each cow. The PF herd comprised 14 Swiss Fleckvieh (SF) and 14 BS cows, which were kept in a free-stall barn throughout the winter; barn-ventilated hay was offered ad libitum during the lactation period. This herd was allocated 15·7 ha of AL. After calving in spring, the PF cows grazed on semi-continuous pastures; they consumed an average of 285 kg of concentrate per lactation. The IF cows of the BS breed produced significantly more energy-corrected milk (ECM) per standard lactation compared with PF cows (8750 v. 5610 kg), more milk fat (350 v. 213 kg) and more milk protein (306 v. 203 kg). However, the milk of PF cows had higher levels of conjugated linoleic acid (CLA) (1·9 v. 0·6 g/100 g fat) and ω−3 fatty acids (1·7 v. 0·9 g/100 g fat) than the milk of the IF cows. The calving interval (378 v. 405 days) and the empty time (87 v. 118 days) of the BS breed were significantly shorter in the PF in comparison with that of the IF production system. The IF herd yielded significantly higher ECM/ha AL and year (12 716 v. 10 307 kg), and showed a higher feed efficiency (1·3 v. 1·1 kg ECM/kg of total dry matter intake (DMI)). The productivity per hour was roughly similar in the two systems (IF: 76 v. PF: 73 kg milk/h). The PF system resulted in higher labour income compared with the IF system (20·7 v. 13·4 €/h), but the difference was not significant. In conclusion, land productivity and efficiency were higher with the IF herd than the PF herd due to the higher energy intake per kg feed. However, within the given conditions, the more interesting case, economically, might be the reduced costs and improved milk quality of the PF system rather than the increased milk yield of the IF cows.

Description: Modern geoinformatic techniques allow the automated creation of detailed glacier inventory data from glacier outlines and digital terrain models (DTMs). Once glacier entities are defined and an appropriate DTM is available, several methods exist to derive the inventory data (e.g. minimum, maximum and mean elevation; mean slope and aspect) for each glacier from digital intersection of both datasets. Compared to the former manual methods, the new grid-based statistical calculations are very fast and reproducible. The major aim of this contribution is to help in standardizing the related calculations to enhance the integrity of the Global Land Ice Monitoring from Space (GLIMS) database. The recommendations were prepared by a working group and also contribute to the European Space Agency project GlobGlacier. The document follows the former UNESCO manual for the production of the World Glacier Inventory published in 1970, identifies the potential pitfalls, and describes the differences from the former methods of compilation. The online background material for this paper (see http://www.glims.org) contains example scripts for calculation of each parameter and will be updated when required.

Description: Deriving glacier outlines from satellite data has become increasingly popular in the past decade. In particular when glacier outlines are used as a base for change assessment, it is important to know how accurate they are. Calculating the accuracy correctly is challenging, as appropriate reference data (e.g. from higher-resolution sensors) are seldom available. Moreover, after the required manual correction of the raw outlines (e.g. for debris cover), such a comparison would only reveal the accuracy of the analyst rather than of the algorithm applied. Here we compare outlines for clean and debris-covered glaciers, as derived from single and multiple digitizing by different or the same analysts on very high- (1 m) and medium-resolution (30 m) remote-sensing data, against each other and to glacier outlines derived from automated classification of Landsat Thematic Mapper data. Results show a high variability in the interpretation of debris-covered glacier parts, largely independent of the spatial resolution (area differences were up to 30%), and an overall good agreement for clean ice with sufficient contrast to the surrounding terrain (differences ∼5%). The differences of the automatically derived outlines from a reference value are as small as the standard deviation of the manual digitizations from several analysts. Based on these results, we conclude that automated mapping of clean ice is preferable to manual digitization and recommend using the latter method only for required corrections of incorrectly mapped glacier parts (e.g. debris cover, shadow).

Description: Glacier inventories provide the baseline data to perform climate-change impact assessment on a regional scale in a consistent and spatially representative manner. In particular, a more accurate calculation of the current and future contribution to global sea-level rise from heavily glacierized regions such as Alaska is much needed. We present a new glacier inventory for a large part of western Alaska (including Kenai Peninsula and the Tordrillo, Chigmit and Chugach mountains), derived from nine Landsat Thematic Mapper scenes acquired between 2005 and 2009 using well-established automated glacier-mapping techniques (band ratio). Because many glaciers are covered by optically thick debris or volcanic ash and partly calve intowater, outlineswere manually edited in these wrongly classified regions during post-processing. In total we mapped ~8830 glaciers (〉0.02 km2) with a total area of ~16 250 km2. Large parts of the area (47%) are covered by a few (31) large (〉100 km2) glaciers, while glaciers less than 1 km2 constitute only 7.5% of the total area but 86% of the total number. We found a strong dependence of mean glacier elevation on distance from the ocean and only a weak one on aspect. Glacier area changes were calculated for a subset of 347 selected glaciers by comparison with the Digital Line Graph outlines from the US Geological Survey. The overall shrinkage was ~23% between 1948–57 and 2005–09.

Description: Meltwater from glaciers in the European Alps plays an important role in hydropower production, and future glacier development is thus of economic interest. However, an up-to-date and alpine-wide inventory for accurate assessment of glacier changes or modelling of future glacier development has not hitherto been available. Here we present a new alpine-wide inventory (covering Austria, France, Italy and Switzerland) derived from ten Landsat Thematic Mapper (TM) scenes acquired within 7 weeks in 2003. Combined with the globally available digital elevation model from the Shuttle Radar Topography Mission, topographic inventory parameters were derived for each of the 3770 mapped glaciers, covering 2050 km2. The area-class frequency distribution is very similar in all countries, and a mean northerly aspect (NW, N, NE) is clearly favoured (arithmetic counting). Mean glacier elevation is ~2900 m, with a small dependence on aspect. The total area loss since the previous glacier inventory (acquired around 1970±15 years) is roughly one-third, yielding a current area loss rate of ~2%a–1. Digital overlay of the outlines from the latest Austrian glacier inventory revealed differences in the interpretation of glacier extents that prohibit change assessment. A comparison of TM-derived outlines with manually digitized extents on a high-resolution IKONOS image returned 1.5% smaller glaciers with TM.