Glaciological and geodetic mass balance of ten long-term glaciers in Norway
Summary: This study provided homogenised data series of glaciological and geodetic mass balance for the ten glaciers in Norway with long-term observations. In total, 21 periods of data were compared. Uncertainties were quantified for relevant sources of errors, both in the glaciological and geodetic series. The reanalysis processes altered seasonal, annual and cumulative as well as ELA and AAR values for many of the years for the 10 glaciers presented.
The Cryosphere Discuss., 9, 6581-6626, doi:10.5194/tcd-9-6581-2015, 2015
Modeling Antarctic subglacial lake filling and drainage cycles
Summary: We examine the development and drainage of subglacial lakes in the Antarctic using a finite element hydrology model. Model outputs show development of slow-moving pressure waves initiated from water funneled from a large catchment into the ice stream. Lake drainage occurs due to downstream channel formation and changing system hydraulic gradients. These model outputs have implications for ice stream dynamics and interpretation of satellite altimetry data over subglacial lake regions.
The Cryosphere Discuss., 9, 6545-6579, doi:10.5194/tcd-9-6545-2015, 2015
Characterizing Arctic sea ice topography using high-resolution IceBridge data
Summary: This study provides an analysis of Arctic sea ice topography using high resolution, three-dimensional, surface elevation data from the NASA Operation IceBridge Airborne Topographic Mapper (ATM) laser altimeter. We describe and implement a newly developed surface feature-picking algorithm and derive novel information regarding the height, volume and geometry of surface features over the western Arctic sea ice cover.
The Cryosphere Discuss., 9, 6495-6543, doi:10.5194/tcd-9-6495-2015, 2015
Multi-method observation and analysis of an impulse wave and tsunami caused by glacier calving
The Cryosphere Discuss., 9, 6471-6493, doi:10.5194/tcd-9-6471-2015, 2015
Modeling debris-covered glaciers: extension due to steady debris input
Summary: Mountains erode and shed rocks down slope. When these rocks (debris) fall on glacier ice they can suppress ice melt. By protecting glaciers from melt, debris can make glaciers extend to lower elevations. Using mathematical models of glaciers and debris deposition we find that debris can more than double the length of glaciers. The amount of debris deposited on the glacier, which scales with mountain height and steepness, is the most important control on debris-covered glacier length and volume.
The Cryosphere Discuss., 9, 6423-6470, doi:10.5194/tcd-9-6423-2015, 2015
Growth of a young pingo in the Canadian Arctic observed by RADARSAT-2 interferometric satellite radar
Summary: We describe the growth of a previously unreported very large diameter pingo in the Tuktoyaktuk Coastlands. Analysis of historical data showed that ground uplift initiated sometime between 1935 and 1951 following lake drainage and is largely caused by the growth of intrusive ice. This study demonstrates that satellite radar can successfully contribute to understanding the dynamics of terrain uplift in response to permafrost aggradation and ground ice development in remote polar environments.
The Cryosphere Discuss., 9, 6395-6421, doi:10.5194/tcd-9-6395-2015, 2015
Greenland Ice Sheet seasonal and spatial mass variability from model simulations and GRACE (2003–2012)
Summary: We compared satellite-derived estimates of spatial and seasonal variations in Greenland Ice Sheet mass with a set of model simulations, revealing an agreement between models and satellite estimates for the ice-sheet-wide seasonal fluctuations in mass, but disagreement at finer spatial scales. The model simulations underestimate low-elevation mass loss. Improving the ability of models to capture variations and trends in Greenland Ice Sheet mass is important for estimating future sea level rise.
The Cryosphere Discuss., 9, 6345-6393, doi:10.5194/tcd-9-6345-2015, 2015
Assessment of error in satellite derived lead fraction in Arctic
Summary: Accurate observations of lead fraction are of high importance for model evaluation and/or assimilation into models. In this work consistent quantitative error estimation of existing lead fraction dataset obtained from passive microwave observations is completed using Synthetic Aperture Radar data. A significant bias in the dataset is found, and possible improvement in the methodology is suggested, so that the pixel-wise error is reduced by a factor of 2 on average.
The Cryosphere Discuss., 9, 6315-6344, doi:10.5194/tcd-9-6315-2015, 2015
Acquisition of isotopic composition for surface snow in East Antarctica and the links to climatic parameters
Summary: The relationship between water isotope ratios and temperature is investigated in precipitation snow at Vostok and Dome C, as well as in surface snow along traverses. The temporal slope of the linear regression for the precipitation is smaller than the geographical slope. Thus, using the latter could lead to an underestimation of past temperature changes. The processes active at remote sites (best glacial-analogues) are explored through a combination of water isotopes in short snow pits.
The Cryosphere Discuss., 9, 6275-6313, doi:10.5194/tcd-9-6275-2015, 2015
Evidence of recent changes in the ice regime of lakes in the Canadian High Arctic from spaceborne satellite observations
The Cryosphere Discuss., 9, 6223-6274, doi:10.5194/tcd-9-6223-2015, 2015
Antarctic slush-ice algal accumulation not quantified through conventional satellite imagery: Beware the ice of March
The Cryosphere Discuss., 9, 6187-6222, doi:10.5194/tcd-9-6187-2015, 2015
Strong ELA increase causes fast mass loss of glaciers in central Spitsbergen
Summary: Svalbard is one of the major terrestrial ice repositories in the Arctic. This paper characterizes response of glaciers in its central part (Dickson Land) to climate change. After the Little Ice Age termination all ice masses have been retreating. Their recent fast thinning contributes strongly to total Svalbard mass balance despite their negligible proportion to toal ice area. These negative changes were linked to 400 m rise of equilibrium line due to climate warming.
The Cryosphere Discuss., 9, 6153-6185, doi:10.5194/tcd-9-6153-2015, 2015
Potential genesis and implications of calcium nitrate in Antarctic snow
Summary: Our results show a strong association between calcium and nitrate ions in snow from two different regions that are >2000 km apart in East Antarctica. Such association could have formed during the interaction between long-range transported dust with the atmospheric nitrate. This study also implies that apart from other well-known sources of nitrate in Antarctica, nitrate associated with mineral dust could form a significant portion of total nitrate deposited in Antarctic snow.
The Cryosphere Discuss., 9, 6125-6151, doi:10.5194/tcd-9-6125-2015, 2015
Anisotropy of seasonal snow measured by polarimetric phase differences in radar time series
Summary: Four years of anisotropy measurements of seasonal snow are presented in the paper. The anisotropy was measured every 4 hours with a ground based polarimetric radar. An electromagnetic model has been developed to measured the anisotropy with radar instruments from ground and from space. The anisotropic permittivity was derived with Maxwell-Garnett type mixing formulas which are shown to be equivalent with series expansions of the permittivity tensor based on spatial correlation function of snow.
The Cryosphere Discuss., 9, 6061-6123, doi:10.5194/tcd-9-6061-2015, 2015
A Retrospective, Iterative, Geometry-Based (RIGB) tilt correction method for radiation observed by Automatic Weather Stations on snow-covered surfaces: application to Greenland
Summary: We identify and correct station tilt induced biases in insolation observed by the Automatic Weather Stations on the Greenland Ice Sheet. Without tilt correction, only 40 % of clear days have the correct solar noon time (±0.5 h). The largest hourly bias exceeds 20 %. We estimate the tilt angles based on solar geometric relationship between insolation observed on a horizontal surface and that on a tilted surface, and produce shortwave radiation and albedo that agree better with independent datasets.
The Cryosphere Discuss., 9, 6025-6060, doi:10.5194/tcd-9-6025-2015, 2015
Two cases of aerodynamic adjustment of sastrugi
Summary: This study presents observational characterization of interactions between wind-induced surface roughness and aeolian erosion over a rough surface in coastal East Antarctica. It is shown that the drag caused by small-scale roughness elements can significantly affects the aeolian snow mass flux during an erosion event, depending on the ability of the surface to adjust according to the main wind. Such measurements are essential to improve parameterization schemes for aeolian snow transport model.
The Cryosphere Discuss., 9, 6003-6024, doi:10.5194/tcd-9-6003-2015, 2015
Improved measurement of ice layer density in seasonal snowpacks
Summary: Ice layers in snowpacks introduce uncertainty in satellite derived estimates of snow water equivalent, have ecological impacts on plants and animals, and change the thermal and vapour transport properties of the snowpack. Here we present a new field method, for measuring the density of ice layers caused by melt or rain-on-snow events. The method was used in the Arctic and mid-latitudes; the mean measured ice layer density was significantly higher than values typically used in the literature.
The Cryosphere Discuss., 9, 5979-6002, doi:10.5194/tcd-9-5979-2015, 2015
Soil temperature-threshold based runoff generation processes in a permafrost catchment
Summary: In cold regions, a comprehensive understanding of the runoff generation mechanism at various scales and within different environments still remains elusive, which is one of the most challenging obstructions in the solution of hydrological scale issues and the development of distributed hydrological models. The traditional theory of nonlinear water-storage capacity curve is obviously not suitable to permafrost catchments in which active soil freezing-thawing cycle have important effects on runoff
The Cryosphere Discuss., 9, 5957-5978, doi:10.5194/tcd-9-5957-2015, 2015
Brief Communication: Twelve-year cyclic surging episode at Donjek Glacier in Yukon, Canada
Summary: We identified twelve-year cyclic surging episode at Donjek Glacier in Yukon, Canada. The surging area is limited within the ~ 20 km section from the terminus, where the flow width is significantly narrower than upstream. Our results suggest a strong control of the valley constriction on the surge dynamics.
The Cryosphere Discuss., 9, 5943-5955, doi:10.5194/tcd-9-5943-2015, 2015
neXtSIM: a new Lagrangian sea ice model
Summary: The Arctic sea-ice cover has changed drastically over the last decades. Associated with these changes is a shift in dynamical regime seen by an increase of extreme fracturing events and an acceleration of sea-ice drift. In this paper we present a new sea ice model that is capable of simulating both sea ice drift and deformation as observed from satellite, with similar spatial and temporal scaling properties.
The Cryosphere Discuss., 9, 5885-5941, doi:10.5194/tcd-9-5885-2015, 2015
Analysis of the mass balance time series of glaciers in the Italian Alps
The Cryosphere Discuss., 9, 5849-5883, doi:10.5194/tcd-9-5849-2015, 2015
Small-scale disturbances in the stratigraphy of the NEEM ice core: observations and numerical model simulations
Summary: In this study we present an analysis of small scale folds observed in the NEEM ice core, North Greenland, discuss their characteristics and frequency and present examples of typical fold structures. Numerical modelling of crystal viscoplasticity deformation and dynamic recrystallisation was used to improve the understanding of the formation of the observed structures during deformation. We conclude that the observed folds are a consequence of localized deformation at the boundaries of kink bands
The Cryosphere Discuss., 9, 5817-5847, doi:10.5194/tcd-9-5817-2015, 2015
Simulating the climatic mass balance of Svalbard glaciers from 2003 to 2013 with a high-resolution coupled atmosphere-glacier model
Summary: A high-resolution, coupled atmosphere - climatic mass balance (CMB) model is applied to Svalbard for the period 2003 to 2013. The mean CMB during this period is negative, but displays large spatial and temporal variations. Comparison with observations on different scales shows a good overall model performance, except for one particular glacier, where wind strongly affects the spatial patterns of CMB. The model also shows considerable sensitivity to model resolution, especially on local scales.
The Cryosphere Discuss., 9, 5775-5815, doi:10.5194/tcd-9-5775-2015, 2015
Microwave snow emission modeling uncertainties in boreal and subarctic environments
The Cryosphere Discuss., 9, 5719-5773, doi:10.5194/tcd-9-5719-2015, 2015
Snow on Arctic sea ice: model representation and last decade changes
Summary: The snow cover on Arctic sea ice is subject to vast changes due to a warming climate. In this study, we assess last decade changes of Arctic snow depth (SD) on sea-ice simulated by an Arctic general circulation model. North of 76 N, the model SD is on average 3 cm thicker than radar SD measurements. In the last decade, the mean regional SD decreased 21 % mainly in first-year ice areas. Surface snow sublimation and melt are the dominant processes responsible of this decline.
The Cryosphere Discuss., 9, 5681-5718, doi:10.5194/tcd-9-5681-2015, 2015
Anomalously-dense firn in an ice-shelf channel revealed by wide-angle radar
Summary: The thickness of ice shelves is typically inferred using hydrostatic equilibrium which requires knowledge of the firn density. Here, we infer density from wide-angle radar using a novel algorithm including traveltime inversion and raytracing. We find that firn is denser inside a 2 km wide ice-shelf channel which is confirmed by optical televiewing of two boreholes. Such horizontal density variations must be accounted for when using the hydrostatic ice thickness for determining basal melt rate.
The Cryosphere Discuss., 9, 5647-5680, doi:10.5194/tcd-9-5647-2015, 2015
The darkening of the Greenland ice sheet: trends, drivers and projections (1981–2100)
Summary: - Summer surface albedo over Greenland decreased at a rate of 0.02/decade between 1996 and 2012 - The decrease is due to snow grain growth, the expansion of bare ice areas, and to trends in light-absorbing impurities on snow and ice surfaces -Neither aerosol models nor in-situ observations indicate increasing trends in impurities in the atmosphere over Greenland - Albedo projections through the end of the century under different warming scenarios consistently point to continued darkening
The Cryosphere Discuss., 9, 5595-5645, doi:10.5194/tcd-9-5595-2015, 2015
A comprehensive interpretation of the NEEM basal ice build-up using a multi parametric approach
Summary: This first multi-parametric analysis of the basal ice layer of the NEEM ice core reveals that its formation does not result from a mixing process between local relict ice and the deepest ice layers of the advancing ice sheet during its growth phase. Instead, it is shown that the basal sequence partly originates from melting and refreezing processes acting at the ice-bedrock interface under a well-developed ice-sheet. These have partially destroyed the paleoclimatic records of the ice.
The Cryosphere Discuss., 9, 5555-5593, doi:10.5194/tcd-9-5555-2015, 2015
Seasonal sea ice predictions for the Arctic based on assimilation of remotely sensed observations
Summary: The manuscript describes the use of remotely sensed sea ice observations for the initialization of seasonal sea ice predictions. Among other observations, CryoSat-2 ice thickness is, to our knowledge for the first time, utilized. While a direct assimilation with CryoSat ice thickness could improve the predictions only locally, the use an advanced data assimilation system (4dVar) allows to establish a bias correction scheme, which is shown to improve the seasonal predictions Arctic wide.
The Cryosphere Discuss., 9, 5521-5554, doi:10.5194/tcd-9-5521-2015, 2015
Modelling the dynamic response of Jakobshavn Isbræ, West Greenland, to calving rate perturbations
Summary: We implemented a Level-Set Method in the Ice Sheet System Model. This method allows us to dynamically evolve a 2-D/3-D ice front subject to user-defined calving rates. We apply the method to Jakobshavn Isbræ, West Greenland, and study its response to calving rate perturbations. We find its behaviour strongly dependent on the calving rate, which was to be expected. Both reduced basal drag and rheological shear margin weakening sustain the acceleration of this dynamic outlet glacier.
The Cryosphere Discuss., 9, 5485-5520, doi:10.5194/tcd-9-5485-2015, 2015
Retrieval of the thickness of undeformed sea ice from C-band compact polarimetric SAR images
Summary: In this work, we introduced a parameter (“CP-Ratio”) for the retrieval of the thickness of undeformed first-year sea ice that is specifically adapted to compact polarimetric SAR images. Based on a validation using other compact polarimetric SAR images from the Sea of Labrador we found a root mean square error of 8 cm and a maximum correlation coefficient of 0.92 for the retrieval procedure when applying it on level ice of 0.9 m mean thickness.
The Cryosphere Discuss., 9, 5445-5483, doi:10.5194/tcd-9-5445-2015, 2015
Wind tunnel experiments: cold-air pooling and atmospheric decoupling above a melting snow patch
Summary: For the first time, this contribution investigates atmospheric decoupling above melting snow in a wind tunnel study. High-resolution vertical profiles of sensible heat fluxes are measured directly over the melting snow patch. The study shows that atmospheric decoupling is strongly increased in case of topographic sheltering but only for low wind velocities. Then turbulent mixing close to the surface is strongly suppressed, facilitating the formation of cold-air pooling in local depressions.
The Cryosphere Discuss., 9, 5413-5443, doi:10.5194/tcd-9-5413-2015, 2015
An investigation of the influence of supraglacial debris on glacier-hydrology
Summary: Dye-tracing of a debris-covered glacier revealed that its hydrological system was not similar to that of a debris-free glacier. Beneath the thick debris covering the lower glacier the drainage system was mainly inefficient, probably due lower sub-debris melt rates causing a lack of the large inputs required to open efficient channels. However, efficient channels opened by the large melt inputs from the debris-free areas did route water from the moulins above the thick debris.
The Cryosphere Discuss., 9, 5373-5411, doi:10.5194/tcd-9-5373-2015, 2015
Analyzing airflow in static ice caves by using the calcFLOW method
Summary: In the paper a new method to calculate airflow speeds in static ice caves by using air temperature data is presented. As most study sites are in very remote places, where it is often not possible to use sonic anemometers and other devices for the analysis of the cave climate, we show how one can use the given database for calculating airflow speeds. To understand/quantify all elements of the specific cave climate is indispensable for understanding the evolution the ice body in ice caves.
The Cryosphere Discuss., 9, 5291-5326, doi:10.5194/tcd-9-5291-2015, 2015
Semi-automated calibration method for modelling of mountain permafrost evolution in Switzerland
Summary: This paper presents a new semi-automated method to calibrate the 1-D model COUPmodel. It is the first time (as far as we know) that such a method is presented for permafros. It is applied at 6 test sites in the Swiss Alps. In a second step, the calibrated model is used for RCM-based simulations with the climate data specifically downscaled at the borehole scale. The projections of the evolution of permafrost at 6 sites until the end of the century and according to A1B scenario are shown.
The Cryosphere Discuss., 9, 4787-4843, doi:10.5194/tcd-9-4787-2015, 2015
Linking catchment-scale subglacial discharge to subsurface glacially modified waters near the front of a marine terminating outlet glacier using an autonomous underwater vehicle
Summary: Here we pair detailed hydrographic measurements collected with an Autonomous Underwater Vehicle as close as 150 m from the ice/ocean interface of the Sarqardliup sermia/Sarqardleq Fjord system, West Greenland, with modeled and observed subglacial discharge locations and magnitudes. We find evidence of two main types of subsurface glacially modified water localized in space that are consistent with runoff discharged at two locations along the grounding line.
The Cryosphere Discuss., 9, 4583-4624, doi:10.5194/tcd-9-4583-2015, 2015
Tilt error in cryospheric surface radiation measurements at high latitudes: a model study
Summary: The magnitude and makeup of error in cryospheric radiation observations due to small sensor misalignment in in-situ measurements of solar irradiance is evaluated. It is shown that relatively minor sensor misalignments give significant errors in irradiance and hence albedo measurements. The total measurement error introduced by sensor tilt is dominated by the direct component. Significant measurement error can persist also in integrated daily irradiance and albedo.
The Cryosphere Discuss., 9, 4355-4376, doi:10.5194/tcd-9-4355-2015, 2015
Coastal dynamics and submarine permafrost in shallow water of the central Laptev Sea, East Siberia
The Cryosphere Discuss., 9, 3741-3775, doi:10.5194/tcd-9-3741-2015, 2015