Journal: Journal of Glaciology

Abbreviation

J Glaciol

Publisher

International Glaciological Society

Journal Volumes

ISSN

0022-1430
1727-5652

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Publications1 - 10 of 133
  • Mountain glacier velocity variation during a retreat/advance cycle quantified using sub-pixel analysis of ASTER images
    Item type: Journal Article
    Herman, Frédéric; Anderson, Brian; Leprince, Sébastien (2011)
    Journal of Glaciology
  • Modelling spatial patterns of near-surface air temperature over a decade of melt seasons on McCall Glacier, Alaska
    Item type: Journal Article
    Troxler, Patrick; Ayala, Alvaro; Shaw, Thomas E.; et al. (2020)
    Journal of Glaciology
    We examine the spatial patterns of near-surface air temperature (Ta) over a melting glacier using a multi-annual dataset from McCall Glacier, Alaska. The dataset consists of a 10-year (2005–2014) meteorological record along the glacier centreline up to an upper glacier cirque, spanning an elevation difference of 900 m. We test the validity of on-glacier linear lapse rates, and a model that calculates Ta based on the influence of katabatic winds and other heat sources along the glacier flow line. During the coldest hours of each summer (10% of time), average lapse rates across the entire glacier range from −4.7 to −6.7°C km−1, with a strong relationship between Ta and elevation (R2 > 0.7). During warm conditions, Ta shows more complex, non-linear patterns that are better explained by the flow line-dependent model, reducing errors by up to 0.5°C compared with linear lapse rates, although more uncertainty might be associated with these observations due to occasionally poor sensor ventilation. We conclude that Ta spatial distribution can vary significantly from year to year, and from one glacier section to another. Importantly, extrapolations using linear lapse rates from the ablation zone might lead to large underestimations of Ta on the upper glacier areas.
  • Statistical modelling of the surface mass-balance variability of the Morteratsch glacier, Switzerland: strong control of early melting season meteorological conditions
    Item type: Journal Article
    Zekollari, Harry; Huybrechts, Philippe (2018)
    Journal of Glaciology
    In this study we analyse a 15-year long time series of surface mass-balance (SMB) measurements performed between 2001 and 2016 in the ablation zone of the Morteratsch glacier complex (Engadine, Switzerland). For a better understanding of the SMB variability and its causes, multiple linear regressions analyses are performed with temperature and precipitation series from nearby meteorological stations. Up to 85% of the observed SMB variance can be explained by the mean May–June–July temperature and the total precipitation from October to March. A new method is presented where the contribution of each month's individual temperature and precipitation to the SMB can be examined in a total sample of 224 (16.8 million) combinations. More than 90% of the observed SMB can be explained with particular combinations, in which the May–June–July temperature is the most recurrent, followed by October temperature. The role of precipitation is less pronounced, but autumn, winter and spring precipitation are always more important than summer precipitation. Our results indicate that the length of the ice ablation season is of larger importance than its intensity to explain year-to-year variations. The widely used June–July–August temperature index may not always be the best option to describe SMB variability through statistical correlation.
  • Reanalysing the 2007-19 glaciological mass-balance series of Mera Glacier, Nepal, Central Himalaya, using geodetic mass balance
    Item type: Journal Article
    Wagnon, Patrick; Brun, Fanny; Khadka, Arbindra; et al. (2021)
    Journal of Glaciology
    The 2007-19 glaciological mass-balance series of Mera Glacier in the Everest Region, East Nepal, is reanalysed using the geodetic mass balance assessed by differencing two DEMs obtained from Pléiades stereo-images acquired in November 2012 and in October 2018. The glaciological glacier-wide annual mass balance of Mera Glacier has to be systematically decreased by 0.11 m w.e. a-1 to match the geodetic mass balance. We attribute part of the positive bias of the glaciological mass balance to an over-estimation of the accumulation above 5520 m a.s.l., likely due to a measurement network unable to capture its spatial variability. Over the period 2007-19, Mera Glacier has lost mass at a rate of-0.41 ± 0.20 m w.e. a-1, in general agreement with regional averages for the central Himalaya. We observe a succession of negative mass-balance years since 2013. Copyright © The Author(s), 2020. Published by Cambridge University Press.
  • Glacier-dammed lake outburst events of Gornersee, Switzerland
    Item type: Journal Article
    Huss, Matthias; Bauder, Andreas; Werder, Mauro; et al. (2007)
    Journal of Glaciology
    Gornersee, Switzerland, is an ice-marginal lake, which drains almost every year, subglacially, within a few days. We present an analysis of the lake outburst events between 1950 and 2005, as well as results of detailed field investigations related to the lake drainage in 2004 and 2005. The latter include measurements of lake geometry, water pressure in nearby boreholes and glacier surface motion. A distributed temperature-index melt model coupled to a linear-reservoir runoff model is used to calculate hourly discharge from the catchment of Gornergletscher in order to distinguish between the melt/precipitation component and the outburst component of the discharge hydrograph. In this way, drainage volume and timing are determined. From 1950 there is a clear trend for the outburst flood to occur earlier in the melt season, but there is no trend in lake discharge volumes. Peak discharges from the lake lie significantly below the values obtained using the empirical relation proposed by Clague and Mathews (1973). The shapes of the 2004 and 2005 lake outflow hydrographs differ substantially, suggesting different drainage mechanisms. From water balance considerations we infer a leakage of the glacier-dammed lake in 2005, starting 1 week prior to the lake outburst. During the drainage events, up to half of the lake water is temporarily stored in the glacial system, causing substantial uplift of the glacier surface.
  • Mass-balance changes of the debris-covered glaciers in the Langtang Himal, Nepal, from 1974 to 1999
    Item type: Journal Article
    Pellicciotti, Francesca; Stephan, Christa; Miles, Evan; et al. (2015)
    Journal of Glaciology
  • Ice thickness measurements and volume estimates for glaciers in Norway
    Item type: Journal Article
    Andreassen, Liss M.; Huss, Matthias; Melvold, Kjetil; et al. (2015)
    Journal of Glaciology
  • Evidence of log-periodic oscillations and increasing icequake activity during the breaking-off of large ice masses
    Item type: Journal Article
    Faillettaz, Jérome; Pralong, Antoine; Funk, Martin; et al. (2008)
    Journal of Glaciology
  • SHIMP The subglacial hydrology model intercomparison Project
    Item type: Journal Article
    de Fleurian, Basile; Werder, Mauro; Beyer, Sebastian; et al. (2018)
    Journal of Glaciology
    Subglacial hydrology plays a key role in many glaciological processes, including ice dynamics via the modulation of basal sliding. Owing to the lack of an overarching theory, however, a variety of model approximations exist to represent the subglacial drainage system. The Subglacial Hydrology Model Intercomparison Project (SHMIP) provides a set of synthetic experiments to compare existing and future models. We present the results from 13 participating models with a focus on effective pressure and discharge. For many applications (e.g. steady states and annual variations, low input scenarios) a simple model, such as an inefficient-system-only model, a flowline or lumped model, or a porous-layer model provides results comparable to those of more complex models. However, when studying short term (e.g. diurnal) variations of the water pressure, the use of a two-dimensional model incorporating physical representations of both efficient and inefficient drainage systems yields results that are significantly different from those of simpler models and should be preferentially applied. The results also emphasise the role of water storage in the response of water pressure to transient recharge. Finally, we find that the localisation of moulins has a limited impact except in regions of sparse moulin density.
  • Terminus dynamics at an advancing glacier: Taku Glacier, Alaska
    Item type: Journal Article
    Truffer, Martin; Motyka, Roman J.; Hekkers, Michael; et al. (2009)
    Journal of Glaciology
    Taku Glacier, Alaska, USA, is currently in the advance stage of the tidewater glacier cycle. We investigated the near-terminus dynamics by measuring surface velocities, surface elevation changes, ice thickness and ablation. Velocities vary on sub-daily, diurnal, seasonal and interannual timescales. Flowline modeling shows that the modeled surface velocities are sensitive to changes in till yield strength and thus effective basal pressures. The glacier bed deepens in the up-glacier direction and this imposes a minimum subglacial water pressure necessary for water to drain along the bed. In a simple model we impose water-pressure gradients based on phreatic surfaces of constant slopes to simulate the winter–summer transitions. This proves sufficient to explain an observed early-season switch from compressional to block flow. Velocities also vary between years. Changing basal conditions can result in lower horizontal velocities, which decrease the ice supply to the terminus and result in temporary surface lowering. But a decrease in ice flux to the terminus must lead to ice storage further upstream, and that ice mass will eventually reach the terminus. This can explain the observed episodic nature of terminus advance.
Publications1 - 10 of 133