Recent changes in north-west Greenland climate documented by NEEM shallow ice core data and simulations, and implications for past temperature reconstructions
Summary: The deep NEEM ice core provides the oldest Greenland ice core record,motivating improved understanding of the response of ice core records to local climate. Here, we focus on shallow ice cores providing a stack record of accumulation and water stable isotopes spanning the past centuries. For the first time, we document the ongoing warming in a Greenland ice core. By combining our data with other Greenland ice cores and model results, we characterize the spatio-temporal patterns of variability.
V. Masson-Delmotte, H. C. Steen-Larsen, P. Ortega, D. Swingedouw, T. Popp, B. M. Vinther, H. Oerter, A. E. Sveinbjornsdottir, H. Gudlaugsdottir, J. E. Box, S. Falourd, X. Fettweis, H. Gallée, E. Garnier, J. Jouzel, A. Landais, B. Minster, N. Paradis, A. Orsi, C. Risi, M. Werner, and J. W. C. White The Cryosphere Discuss., 9, 655-717, 2015 AbstractDiscussion Paper (PDF, 6129 KB)Supplement (608 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for TC
29 Jan 2015
Modeling of crack propagation in weak snowpack layers using the discrete element method
Summary: We proposed a new approach to characterize the dynamic phase of crack propagation in weak snowpack layers as well as fracture arrest propensity by means of numerical "Propagation Saw Test" simulations based on the discrete element method. Crack propagation speed and distance before fracture arrest were derived from the simulations for different snowpack configurations and mechanical properties. Numerical and experimental results were compared and the mechanical processes at play were discussed.
Can we retrieve a clear paleoclimatic signal from the deeper part of the EPICA Dome C ice core?
Summary: The oldest paleoclimatic information is buried within the lowermost layers of deep ice cores. It is therefore essential to judge how deep these records remain unaltered. We study the bottom 60 meters of the EPICA Dome C ice core from central Antarctica to show that the paleoclimatic signal is only affected at the small scale (decimeters) in terms of some of the global ice properties. However our data suggest that the time scale has been considerably distorted by mechanical stretching.
J.-L. Tison, M. de Angelis, G. Littot, E. Wolff, H. Fischer, M. Hansson, M. Bigler, R. Udisti, A. Wegner, J. Jouzel, B. Stenni, S. Johnsen, V. Masson-Delmotte, A. Landais, V. Lipenkov, L. Loulergue, J.-M. Barnola, J.-R. Petit, B. Delmonte, G. Dreyfus, D. Dahl-Jensen, G. Durand, B. Bereiter, A. Schilt, R. Spahni, K. Pol, R. Lorrain, R. Souchez, and D. Samyn The Cryosphere Discuss., 9, 567-608, 2015 AbstractDiscussion Paper (PDF, 2759 KB)Supplement (107 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for TC
28 Jan 2015
Changes in the firn structure of the Greenland Ice Sheet caused by recent warming
Summary: This paper presents an assessment of changes in the near-surface structure of the accumulation zone of the Greenland Ice Sheet caused by an increase of melt at higher elevations in the last decade, especially during the unusually warm years of 2010 and 2012. The increase in melt and firn densification complicate the interpretation of changes in the ice volume, and the observed increase in firn ice content may reduce the important meltwater buffering capacity of the Greenland Ice Sheet.
S. de la Peña, I. M. Howat, P. W. Nienow, M. R. van den Broeke, E. Mosley-Thompson, S. F. Price, D. Mair, B. Noël, and A. J. Sole The Cryosphere Discuss., 9, 541-565, 2015 AbstractDiscussion Paper (PDF, 4644 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for TC
27 Jan 2015
Numerical simulation of extreme snow melt observed at the SIGMA-A site, northwest Greenland, during summer 2012
Summary: A physical snowpack model SMAP and in situ meteorological and snow data obtained at site SIGMA-A on the northwest Greenland ice sheet are used to assess surface energy balance during the extreme near-surface snowmelt event around 12 July 2012. We determined that the main factor for the melt event observed at site SIGMA-A was low-level clouds accompanied by a significant temperature increase, which induced surface heating via cloud radiative forcing in the polar region.
M. Niwano, T. Aoki, S. Matoba, S. Yamaguchi, T. Tanikawa, K. Kuchiki, and H. Motoyama The Cryosphere Discuss., 9, 495-539, 2015 AbstractDiscussion Paper (PDF, 1981 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for TC
20 Jan 2015
Snowfall in the Himalayas: an uncertain future from a little-known past
Summary: Snow and ice provide large amounts of meltwater to the Indus, Ganges and Brahmaputra rivers. In this study we show that climate change will reduce the amount of snow falling in the Himalayas, Hindu Kush and Karakoram substantially. The limited number of observations in remote, upper-level terrain makes it difficult to get a complete overview of the situation today, but our results indicate that by 2071–2100 snowfall may be reduced by 30–70 % with the strongest anthropogenic forcing scenario.
Decapitation of high-altitude glaciers on the Tibetan Plateau revealed by ice core tritium and mercury records
S. C. Kang, F. Y. Wang, U. Morgenstern, Y. L. Zhang, B. Grigholm, S. Kaspari, M. Schwikowski, J. W. Ren, T. D. Yao, D. H. Qin, and P. A. Mayewski The Cryosphere Discuss., 9, 417-440, 2015 AbstractDiscussion Paper (PDF, 5028 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for TC
16 Jan 2015
Modelling annual mass balances of eight Scandinavian glaciers using statistical models
Summary: We employ statistical models to model annual glacier mass balances of 8 Scandinavian glaciers as function of ablation-season temperature and accumulation-season precipitation
Relative importances of accumulation-season precipitation and ablation-season temperature vary in time
Relative importance is influenced by AMO and NAO
Climate sensitivities are comparable to degree day models but lower than energy balance models
For the future (2050, 2100) all average annual mass balances are negative
Mapping snow-depth from manned-aircraft on landscape scales at centimeter resolution using Structure-from-Motion photogrammetry
Summary: This paper presents a photogrammetric method for measuring topography from manned aircraft with an accuracy of 30 cm and repeatability of 8 cm, at significantly lower cost than other methods. Here we created difference maps to demonstrate that we could measure snow depth with an accuracy of 10 cm compared to over 6000 snow-probe measurements on the ground, but do so over entire watersheds at 10-20 cm spatial resolution rather than just a few transects.
A 3-D simulation of drifting snow in the turbulent boundary layer
Summary: Drifting snow is a frequent occurrence natural phenomenon at high latitudes, which has a non-ignorable contribution to the mass balance of ice sheets as well as hydrological balance. The snow drifting process in the turbulent boundary layer is performed and the snow streamers are reproduced. In addition, the particles' velocities along spanwise direction is one order of magnitude smaller than streamwise direction and the diameter distribution along height shows a stratification structure.
Atmospheric and oceanic forcing of Larsen C Ice Shelf thinning
Summary: Many ice shelves on the Antarctic Peninsula have collapsed in recent decades. The surface of Larsen C Ice Shelf is lowering, but the cause of this has not been understood. This study uses data from eight radar surveys to show that the lowering is caused by both ice loss and a loss of air from the ice shelf's snowpack. At least two different processes are causing the lowering. It is possible that this ice shelf will collapse within decades if its ice front is destabilised.
P. R. Holland, A. Brisbourne, H. F. J. Corr, D. McGrath, K. Purdon, J. Paden, H. A. Fricker, F. S. Paolo, and A. H. Fleming The Cryosphere Discuss., 9, 251-299, 2015 AbstractDiscussion Paper (PDF, 6747 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for TC
13 Jan 2015
A sensitivity study of fast outlet glaciers to short timescale cyclical perturbations
Analysis of long-term precipitation pattern over Antarctica derived from satellite-borne radar
Summary: The aim of this work is to show that the CloudSat Cloud Profiling Radar (CPR) can be a valuable source of snowfall rate data in Antarctica that can be used at different temporal scales. Two years of CloudSat data over Antarctica are analyzed and two different approaches for precipitation estimates are considered. The results show that CPR can provide valuable support to the sparse network of ground-based instruments both for numerical model validation and climatological studies.
L. Milani, F. Porcù, D. Casella, S. Dietrich, G. Panegrossi, M. Petracca, and P. Sanò The Cryosphere Discuss., 9, 141-182, 2015 AbstractDiscussion Paper (PDF, 2886 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for TC
08 Jan 2015
Future projections of the climate and surface mass balance of Svalbard with the regional climate model MAR
Dissolved organic carbon (DOC) in Arctic ground ice
Summary: will be provided later
M. Fritz, T. Opel, G. Tanski, U. Herzschuh, H. Meyer, A. Eulenburg, and H. Lantuit The Cryosphere Discuss., 9, 77-114, 2015 AbstractDiscussion Paper (PDF, 3625 KB)Interactive Discussion (Open, 1 Comment)Manuscript under review for TC
07 Jan 2015
Winter observations of CO2 exchange between sea-ice and the atmosphere in a coastal fjord environment
Theoretical framework for estimating snow distribution through point measurements
Summary: In this article, we present a methodology for the objective evaluation of the error in capturing mean snow depths from point measurements. We show using LIDAR snow depths how the model can be used for assisting the design of survey strategies such that the error is minimized or an estimation threshold is achieved. Furthermore, the model can be extended to other spatially distributed snow variables (e.g., SWE) whose statistical properties are comparable to those of snow depth.
Evolution of surface velocities and ice discharge of Larsen B outlet glaciers from 1995 to 2013
Summary: We present new analysis of satellite data showing the variability of glacier velocities in the Larsen B area, Antarctic Peninsula, back to 1995. Velocity data and estimates of ice thickness are used to derive ice discharge at different epochs. Velocities of the glaciers remain to date well above the velocities of the pre-collapse period. The response of individual glaciers differs and velocities show significant temporal fluctuations, implying major variations in ice discharge and mass balance.
J. Wuite, H. Rott, M. Hetzenecker, D. Floricioiu, J. De Rydt, G. H. Gudmundsson, T. Nagler, and M. Kern The Cryosphere Discuss., 8, 6271-6301, 2014 AbstractDiscussion Paper (PDF, 7942 KB)Interactive Discussion (Open, 0 Comments)Manuscript under review for TC
23 Dec 2014
How robust and (un)certain are regional climate models over the Himalayas?
Summary: This paper brings in and debates issues on
1. Uncertainty in regional climate models for glaciological/hydrological studies
2. Bias correction employed on model outputs provide improved results
3. Provides an insight for glacier research
Brief Communication: 2014 velocity and flux for five major Greenland outlet glaciers using ImGRAFT and Landsat-8
Summary: We use 2014 Landsat-8 imagery in combination with a newly developed feature tracking toolbox, ImGRAFT to produce velocity fields and flux for five major Greenland marine terminating glaciers: Helheim, Kangerdlugssuaq, Nioghalvfjerdsbræ, Petermann and Jakobshavn Isbræ. A major finding of the paper documents the increased velocities observed at Jakobshavn Isbræ. We measure velocities over 50m/day which exceed that of the previously recorded maximum.
Influence of weak layer heterogeneity and slab properties on slab tensile failure propensity and avalanche release area
Summary: Slab tensile failure propensity is examined using a mechanical-statistical model of the slab–weak layer (WL) system based on the finite element method. This model accounts for WL heterogeneity, stress redistribution by elasticity of the slab and the slab possible tensile failure. For realistic values of the parameters, the tensile failure propensity is mainly driven by slab properties. Hard and thick snow slabs are more prone to wide–scale crack propagation and thus lead to larger avalanches.
Comparison of aeolian snow transport events and snow mass fluxes between observations and simulations made by the regional climate model MAR in Adélie Land, East Antarctica
A. Trouvilliez, H. Gallée, F. Naaim-Bouvet, C. Genthon, C. Amory, V. Favier, C. Agosta, L. Piard, and H. Bellot The Cryosphere Discuss., 8, 6007-6032, 2014 AbstractDiscussion Paper (PDF, 1504 KB)Interactive Discussion (Open, 2 Comments)Manuscript under review for TC
05 Dec 2014
Weak precipitation, warm winters and springs impact glaciers of south slopes of Mt. Everest (central Himalaya) in the last two decades (1994–2013)
Summary: Climate trends in Himalaya are completely absent at high elevation. We explore the south slopes of Mt Everest though time series reconstructed from 7 stations (2660-5600 m) during 1994-2013. The main increase in temp is concentrated outside of the monsoon, minimum temp increased far more than maximum, while we note a substantial prec weakening. We contribute to change the perspective on which climatic driver (temperature vs. precipitation) led mainly the glacier responses in the last 20 yr
F. Salerno, N. Guyennon, S. Thakuri, G. Viviano, E. Romano, E. Vuillermoz, P. Cristofanelli, P. Stocchi, G. Agrillo, Y. Ma, and G. Tartari The Cryosphere Discuss., 8, 5911-5959, 2014 AbstractDiscussion Paper (PDF, 4918 KB)Supplement (1003 KB)Interactive Discussion (Open, 5 Comments)Manuscript under review for TC
01 Dec 2014
A process-based approach to estimate point snow instability
Thin-ice dynamics and ice production in the Storfjorden polynya for winter-seasons 2002/2003–2013/2014 using MODIS thermal infrared imagery
Summary: The Storfjorden polynya (Svalbard) forms regularly under the influence of strong north-easterly winds. In this study, spatial and temporal characteristics for the period 2002/03 - 2013/14 were inferred from daily calculated thin-ice thickness distributions, based on MODIS ice surface temperatures and ERA-interim reanalysis.
With an estimated average ice production of 28.3 km³/winter, this polynya system is of particular interest regarding its potential contribution to deep water formation.