Revealing glacier flow and surge dynamics from animated satellite image sequences: examples from the Karakoram
Summary: This study uses animations of freely available Landsat images (acquired over 25 years) to reveal glacier flow and surge dynamics in the central Karakoram. The animations provide a holistic view on the timing and variability of glacier dynamics that is hard to obtain by other more quantitative methods. Among others, the study reveals that most surging glaciers are comparably small, steep and debris-free, with a wide range of advance rates and durations, overlapping with non-surge-type glaciers.
The Cryosphere, 9, 2201-2214, doi:10.5194/tc-9-2201-2015, 2015
A new methodology to simulate subglacial deformation of water-saturated granular material
Summary: This paper details a new algorithm for performing computational experiments of subglacial granular deformation. The numerical approach allows detailed studies of internal sediment and pore-water dynamics under shear. Feedbacks between sediment grains and pore water can cause rate-dependent strengthening, which additionally contributes to the plastic shear strength of the granular material. Hardening can stabilise patches of the subglacial beds with implications for landform development.
The Cryosphere, 9, 2183-2200, doi:10.5194/tc-9-2183-2015, 2015
Changing surface–atmosphere energy exchange and refreezing capacity of the lower accumulation area, West Greenland
The Cryosphere, 9, 2163-2181, doi:10.5194/tc-9-2163-2015, 2015
Comparison of a coupled snow thermodynamic and radiative transfer model with in situ active microwave signatures of snow-covered smooth first-year sea ice
Summary: We modeled snow (based on weather variables) to simulate microwave response. The simulated snowpack, and the simulated microwave backscatter response, was compared to observed physical snow and ice properties and the observed microwave response. There was better agreement between the simulated and observed microwave signatures when we applied observed salinity profiles to the simulated snow pack. Without correction for observed salinity, there was less agreement.
The Cryosphere, 9, 2149-2161, doi:10.5194/tc-9-2149-2015, 2015
From Doktor Kurowski's Schneegrenze to our modern glacier equilibrium line altitude (ELA)
Summary: Kurowski suggested in 1891 that ELA is equal to the mean altitude of the glacier when the glacier is in balance. I compare mean altitude with balanced-budget ELA for 103 modern glaciers. Kurowski’s mean altitude is significantly higher (at 95% level) than balanced-budget ELA for 19 outlet and 42 valley glaciers, but not significantly higher for 34 mountain glaciers. The error in Kurowski mean altitude as a predictor of balanced budget might be due to non-linearity in balance gradients.
The Cryosphere, 9, 2135-2148, doi:10.5194/tc-9-2135-2015, 2015
A prognostic model of the sea-ice floe size and thickness distribution
Summary: Sea-ice cover is composed of floes of different sizes and thicknesses, whose distribution varies in space and time, and may affect the interaction between sea ice and the ocean and atmosphere, yet is not represented in climate models. We develop and demonstrate a model for the evolution of the joint distribution of floe sizes and thicknesses, subject to melting and freezing, mechanical interactions between floes, and the fracture of floes by waves, forced by atmospheric and ocean forcing fields.
The Cryosphere, 9, 2119-2134, doi:10.5194/tc-9-2119-2015, 2015
Microwave scattering coefficient of snow in MEMLS and DMRT-ML revisited: the relevance of sticky hard spheres and tomography-based estimates of stickiness
Summary: The paper establishes a theoretical link between two widely used microwave models for snow. The scattering formulations from both models are unified by reformulating their microstructure models in a common framework. The results show that the scattering formulations can be considered equivalent, if exactly the same microstructure model is used. The paper also provides a method to measure a hitherto unknown input parameter for the microwave models from tomography images of snow.
The Cryosphere, 9, 2101-2117, doi:10.5194/tc-9-2101-2015, 2015
Assessment of permafrost distribution maps in the Hindu Kush Himalayan region using rock glaciers mapped in Google Earth
Summary: The extent and distribution of permafrost in the mountainous parts of the Hindu Kush Himalayan (HKH) region are largely unknown. This article provides a first-order assessment of the two available permafrost maps in the HKH region based on the mapping of rock glaciers in Google Earth. The Circum-Arctic Map of Permafrost and Ground Ice Conditions does not reproduce mapped conditions in the HKH region adequately, whereas the Global Permafrost Zonation Index does so with more success.
The Cryosphere, 9, 2089-2099, doi:10.5194/tc-9-2089-2015, 2015
Four decades of glacier variations at Muztagh Ata (eastern Pamir): a multi-sensor study including Hexagon KH-9 and Pléiades data
Summary: Investigations of glacier mass-balance and area changes at Muztagh Ata (eastern Pamir) are based on Hexagon KH-9 (1973), ALOS-PRISM (2009), Pléiades (2013) and Landsat 7 ETM+/SRTM-3 (2000). Surface velocities of Kekesayi Glacier are derived by TerraSAR-X (2011) amplitude tracking. Glacier variations differ spatially and temporally, but on average not significantly for the entire massif. Stagnant Kekesayi and other debris-covered glaciers indicate no visual length changes, but clear down-wasting.
The Cryosphere, 9, 2071-2088, doi:10.5194/tc-9-2071-2015, 2015
The global land shortwave cryosphere radiative effect during the MODIS era
Summary: Our work quantifies the effect of snow/ice cover on Earth's top-of-atmosphere solar energy budget. We used higher resolution MODIS data, combined with microwave retrievals of snow presence and radiative kernels produced from 4 different models for Cryosphere Radiative Effect (CrRE) estimation. We have estimated a global land-based CrRE of about -2.6Wm-2 during 2001-2013, with about 59% of the effect originating from Antarctica. We were also be able to resolve contribution from mountain glaciers.
The Cryosphere, 9, 2057-2070, doi:10.5194/tc-9-2057-2015, 2015
Reducing uncertainties in projections of Antarctic ice mass loss
Summary: Projections of Antarctic dynamics and contribution to sea-level rise are evaluated in the light of intercomparison exercises dedicated to evaluate models' ability of representing coastal changes. Uncertainties in projections can be substantially decreased if a selection of models is made and models that are unqualified for the representation of coastal dynamics are excluded.
The Cryosphere, 9, 2043-2055, doi:10.5194/tc-9-2043-2015, 2015
Long-term coastal-polynya dynamics in the southern Weddell Sea from MODIS thermal-infrared imagery
Summary: We established a 13-year-long MODIS-derived thin-ice thickness data set from which we derived information about polynya dynamics in the southern Weddell Sea. In contrast to other studies, we do not focus on a single region but instead discuss polynya dynamics for the complete coastal area. The higher spatial resolution of MODIS compared to passive-microwave sensors enables us to resolve even very narrow coastal polynyas that would remain otherwise undetected.
The Cryosphere, 9, 2027-2041, doi:10.5194/tc-9-2027-2015, 2015
Elevation change of the Greenland Ice Sheet due to surface mass balance and firn processes, 1960–2014
Summary: The snow layer on top of the Greenland Ice Sheet is changing: it is thickening in the high and cold interior due to increased snowfall, while it is thinning around the margins. The marginal thinning is caused by compaction, and by more melt. This knowledge is important: there are satellites that measure volume change of the ice sheet. It can be caused by increased ice discharge, or by compaction of the snow layer. Here, we quantify the latter, so that we can translate volume to mass change.
The Cryosphere, 9, 2009-2025, doi:10.5194/tc-9-2009-2015, 2015
Precipitation measurement intercomparison in the Qilian Mountains, north-eastern Tibetan Plateau
Summary: The catch ratio of Chinese standard precipitation gauge vs. wind speed relationship for different precipitation types was well quantified by cubic polynomials and exponential functions using 5-year field data in the high-mountain environment of the Tibetan Plateau. The daily precipitation measured by shielded gauges increases linearly with that of unshielded gauges. The pit gauge catches the most local precipitation in rainy season and could be used as a reference in most regions of China.
The Cryosphere, 9, 1995-2008, doi:10.5194/tc-9-1995-2015, 2015
Numerical simulation of formation and preservation of Ningwu ice cave, Shanxi, China
The Cryosphere, 9, 1983-1993, doi:10.5194/tc-9-1983-2015, 2015
Microstructure-based modeling of snow mechanics: a discrete element approach
Summary: This paper deals with a mechanical model that exploits a granular description of the snow microstructure. Its originality is that the geometry of the snow grains and of the inter-granular bonding system are explicitly defined from microtomographic data. It enables to model large deformations controlled by grain-rearrangements, which is of particular interest to study the collapse of weak layers or the characterization of the snowpack with an indenter.
The Cryosphere, 9, 1969-1982, doi:10.5194/tc-9-1969-2015, 2015
Lead detection in Arctic sea ice from CryoSat-2: quality assessment, lead area fraction and width distribution
Summary: Leads in Arctic sea ice have a dominant effect on the exchange between the ocean and the atmosphere. Visual MODIS scenes are used to validate and improve the detection of leads from altimeter measurements of the satellite CryoSat-2. The rarely used maximum power of the returning signal shows the best classification properties. Lead area fraction and width distribution estimates based on CryoSat-2 complement other studies and deepen our understanding of lead characteristics.
The Cryosphere, 9, 1955-1968, doi:10.5194/tc-9-1955-2015, 2015
Projected 21st century changes in snow water equivalent over Northern Hemisphere landmasses from the CMIP5 model ensemble
The Cryosphere, 9, 1943-1953, doi:10.5194/tc-9-1943-2015, 2015
Photopolarimetric retrievals of snow properties
The Cryosphere, 9, 1933-1942, doi:10.5194/tc-9-1933-2015, 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.
The Cryosphere, 9, 1915-1932, doi:10.5194/tc-9-1915-2015, 2015