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Glaciers distinct from the Greenland and Antarctic ice sheets are shrinking rapidly, altering regional hydrology.sup.1, raising global sea level.sup.2 and elevating natural hazards.sup.3. Yet, owing to the scarcity of constrained mass loss observations, glacier evolution during the satellite era is known only partially, as a geographic and temporal patchwork.sup.4,5. Here we reveal the accelerated, albeit contrasting, patterns of glacier mass loss during the early twenty-first century. Using largely untapped satellite archives, we chart surface elevation changes at a high spatiotemporal resolution over all of Earth's glaciers. We extensively validate our estimates against independent, high-precision measurements and present a globally complete and consistent estimate of glacier mass change. We show that during 2000-2019, glaciers lost a mass of 267 [plus or minus] 16 gigatonnes per year, equivalent to 21 [plus or minus] 3 per cent of the observed sea-level rise.sup.6. We identify a mass loss acceleration of 48 [plus or minus] 16 gigatonnes per year per decade, explaining 6 to 19 per cent of the observed acceleration of sea-level rise. Particularly, thinning rates of glaciers outside ice sheet peripheries doubled over the past two decades. Glaciers currently lose more mass, and at similar or larger acceleration rates, than the Greenland or Antarctic ice sheets taken separately.sup.7-9. By uncovering the patterns of mass change in many regions, we find contrasting glacier fluctuations that agree with the decadal variability in precipitation and temperature. These include a North Atlantic anomaly of decelerated mass loss, a strongly accelerated loss from northwestern American glaciers, and the apparent end of the Karakoram anomaly of mass gain.sup.10. We anticipate our highly resolved estimates to advance the understanding of drivers that govern the distribution of glacier change, and to extend our capabilities of predicting these changes at all scales. Predictions robustly benchmarked against observations are critically needed to design adaptive policies for the local- and regional-scale management of water resources and cryospheric risks, as well as for the global-scale mitigation of sea-level rise. Analysis of satellite stereo imagery uncovers two decades of mass change for all of Earth's glaciers, revealing accelerated glacier shrinkage and regionally contrasting changes consistent with decadal climate variability., Author(s): Romain Hugonnet [sup.1] [sup.2] [sup.3] , Robert McNabb [sup.4] [sup.5] , Etienne Berthier [sup.1] , Brian Menounos [sup.6] [sup.7] , Christopher Nuth [sup.5] [sup.8] , Luc Girod [sup.5] , [...]

Knowledge of the ice thickness distribution of glaciers and ice caps is an important prerequisite for many glaciological and hydrological investigations. A wealth of approaches has recently been presented for inferring ice thickness from characteristics of the surface. With the Ice Thickness Models Intercomparison eXperiment (ITMIX) we performed the first coordinated assessment quantifying individual model performance. A set of 17 different models showed that individual ice thickness estimates can differ considerably - locally by a spread comparable to the observed thickness. Averaging the results of multiple models, however, significantly improved the results: on average over the 21 considered test cases, comparison against direct ice thickness measurements revealed deviations on the order of 10 ± 24% of the mean ice thickness (1σ estimate). Models relying on multiple data sets - such as surface ice velocity fields, surface mass balance, or rates of ice thickness change - showed high sensitivity to input data quality. Together with the requirement of being able to handle large regions in an automated fashion, the capacity of better accounting for uncertainties in the input data will be a key for an improved next generation of ice thickness estimation approaches.

Basal conditions play an essential role in the dynamics of outlet glaciers, but direct observations at the bed of glaciers are challenging to obtain. Instead, inverse methods can be used to infer basal parameters from surface observations. Here, we use a simple ice-flow model as a forward model in an inversion scheme to retrieve the spatio-temporally variable basal stress parameter for Hagen Bræ, North Greenland, from 1990 to 2020. Hagen Bræ is a surge-type glacier with up to an order of magnitude variability of winter velocities near the grounding line. We find that downstream changes in the basal stress parameter can explain most of the variation of flow velocity, and we further identify a region of high resistance ~20–40 km from the grounding line. We hypothesise that this region of high resistance plays an important role in controlling glacier discharge. [ABSTRACT FROM AUTHOR]

The relationship between unions, new work practices and organizational performance has been the subject of much debate. Some commentators view unions as inimical to new work practices, whereas others see them as offering channels to facilitate their introduction. It has also been suggested that unions might prevent such practices from attaining their full potential and thereby their enhanced organizational performance. Using data from the third Workplace Industrial Relations Survey and the Employer Manpower Skills Practices Survey, a multinomial logit analysis is undertaken involving proxies for the adoption of flexibility and team working as the dependent variable and a vector of variables (including proxies for unionism) as independent variables. The results indicate that the presence of a closed shop at the workplace inhibits the adoption of flexibility and team working but that the presence of a recognized union is beneficial to their introduction. A binomial logit analysis of financial performance also indicates that the joint effect of union presence and both flexibility and team working on financial performance is positive, even though the single effect of union presence is negative. (Reprinted by permission of the publisher.), Introduction Recent years have seen the introduction of a wide range of innovative human resource management practices by firms in their attempt to attain and sustain competitive advantage in increasingly [...]

This article discusses the effect of recurrent spells upon unemployment duration in Great Britain. It is argued that recurrent spells and long durations are causally related. In particular, evidence is provided to support the proposition that recurrent spells are a partial determinant of unemployment duration. The fact that recurrent spells appear to prolong the duration of unemployment has an obvious implication. There has been a tendency for academics concerned with unemployment to concentrate upon the duration question, sometimes at the expense of information about spell repetition. Yet spell repetition seems to have both a direct and indirect influence upon the length of time an individual spends out of work.

Greenland's peripheral glaciers play a crucial role in a changing climate and related sea-level rise. However, the recent evolution of the ice volume along Greenland's periphery is still poorly understood. The restricted number of geodetic glacier thickness changes on Greenland is probably related to the absence of digital elevation models (DEM) of sufficient accuracy. The AeroDEM representing the surface in the 1970s-80s and the recently released high resolution TanDEM-X DEM (representing 2010-2014) have potential to provide geodetic volume change estimates of many glaciers in Polar Regions. Using these two DEMs, we were able to calculate glacier-specific elevation changes of approximately 1'400 glaciers in West-central Greenland. To appropriately deal with data voids and artifacts occurring in the AeroDEM, we applied a void-filling method that considers the hypsometry of the individual glaciers. Based on the preliminary results, we expect the mean elevation change to be approximately -0.5 m per year from 1985-2010/14, resulting in a sea-level contribution of approximately 39 Gt for the full observation period. A previous ICESat study calculated a mean elevation change of -0.28 m per year from 2003-2008 for West-central Greenland. Here, we discuss the reasons for these significant differences. Additionally, our analysis includes a sound uncertainty assessment considering different sources of random and systematic errors. This study contributes to improve current estimates of glacier ice loss and corresponding contributions to global sea level. [ABSTRACT FROM AUTHOR]

The Tien Shan and Pamir, hosting more than 25'000 glaciers, act as important water towers for the dry, continental lowlands of Central Asia. Most glacier mass balance assessments focus on region-wide, decadal mass changes and only a few address seasonal or annual glacier mass balances. The regional annual variability is thus far poorly understood. However, it is essentially needed to improve our understanding of glacier runoff contribution. Here, multi-annual glacier mass changes derived from remote sensing were complemented with seasonal to annual mass balance series inferred from modelling closely constrained with repeated transient snowline observations on a regional scale. To derive annual time series, transient snowline observations were used to calibrate an accumulation and temperature-index melt model for each year and glacier individually. The modelled decadal mass balance was constrained with glacier specific geodetic mass balances calculated from satellite stereo images. We calculated geodetic mass loss from 2004 to 2012 and annual surface mass balance time series from 2000 to 2017 for the Tien Shan and Pamir. A geodetic mass loss of -0.52 ± 0.53 m w.e. yr-1 was calculated for the Tien Shan and -0.24 ± 0.43 m w.e. yr-1 for the Pamir from 2004 to 2012. First results from transient snowline-constrained modelling confirmed the decadal mass loss ranging from -0.36 ± 0.32 to -0.44 to ± 0.32 m w.e. yr-1 for 2000 to 2017 for the subranges Kyrgyz Ala-Too (Tien Shan), the Pamir-Alay (Pamir) and the Akshiirak range (Tien Shan). Lower rates of mass loss was encountered for the early years of the study period and exceptionally negative balances were found for most glaciers in 2008. Our results show a significant trend to increased mass loss for the Pamir-Alay and the Kyrgyz Ala-Too, accompanied with a moderate increase of the interannual variability with time. Annual variability is similar for the Kyrgyz Ala-Too and Pamir-Alay and is considerably smaller for the Akshiirak massif. For Akshiirak, the interannual variability seems to have increased in recent years, however, no significant trends in mass balance were observed. Our time series, annually tied to transient snowline observations and linked to the geodetic estimates at the decadal scale, enable the analysis of yearly mass balance variability for glaciers in a region with few in situ measurements. Moreover, they deliver important baseline data for in depth analysis of the glacier response to climate fluctuations and enable to analyse the importance of glacier melt contribution to the hydrological cycle with an enhanced temporal resolution. [ABSTRACT FROM AUTHOR]

The Arctic is one of the fastest-warming regions in the world, and Arctic glaciers have been identified as one of the largest sources of global sea level rise in recent years. In addition to sea level rise, Arctic glacier mass loss has implications for local and regional changes in ocean chemistry and circulation, and oceanic and terrestrial ecosystems. In spite of this overall importance, Arctic glacier changes are poorly constrained on a spatial and/or temporal basis, with regional estimates coming either from spatially-coarse gravimetry estimates, extrapolations using sparse satellite altimetry measurements, or extrapolation using in-situ mass balance for small numbers of individual glaciers. While these approaches provide a good picture of changes across the region, they provide limited information about changes on an individual glacier or mountain range scale, or on non-observed glaciers. Newly opened satellite image archives, combined with new processing techniques as well as increased computing power and storage capacity, provide the opportunity to observe and investigate glacier processes and changes regionally on enhanced spatial and temporal scales.Using MMASTER, a processing pipeline based on the MicMac open-source photogrammetry suite, we have processed over 20000 ASTER scenes covering the Arctic over the period 2000-2018. These DEMs, in combination with the recently-released ArcticDEM v3.0 archive and IPY-SPIRIT SPOT5-HRS DEMs, provide an unparalleled spatially- and temporally-resolved picture of glacier elevation and volume changes across the Arctic over the past two decades. Using older images and data sources where available, we provide a longer-term perspective on the changes observed. Finally, we compare our satellite-derived estimates of glacier change in the Arctic to in-situ mass balances and satellite gravimetry. [ABSTRACT FROM AUTHOR]