An analytical model for wind-driven Arctic summer sea ice drift
Summary: We have derived an analytical model for wind-induced sea-ice drift. We allow for partial sea ice cover using the "mixture layer" formulation and explicitly assume an oceanic Ekman layer, separated from the ice by a thin boundary layer. Provided that surface wind field is known, it is very easy to calculate the sea-ice motion using this analytical model. We believe this analytical model is a powerful tool for identifying and quantifying the mechanisms for the Arctic sea-ice variability.
The Cryosphere Discuss., 9, 2101-2133, doi:10.5194/tcd-9-2101-2015, 2015
Active lakes in Antarctica survive on a sedimentary substrate – Part 1: Theory
Summary: We develop a model that simulated the observed filling and draining of active subglacial lakes in Antarctica that suggests the may occurs by the erosion of channels into deformable subglacial sediments, that then deform shut as lake level declines. This contrasts with ice dammed alpine lakes which drain by channels incised into ice. If active subglacial lakes require deformable sediments to fill and drain as observed, then classic radar-based methods of lake detection may fail to find them.
The Cryosphere Discuss., 9, 2053-2099, doi:10.5194/tcd-9-2053-2015, 2015
Overview on radon measurements in Arctic glacier waters
Summary: We present a study of the subglacial component in waters using the natural radioisotope radon. The paper is the result of several years of investigations on a Svalbard glacier and constitutes a first overview on this new technique. The paper is innovative as we are the first to use radon as a tracer for the system of glacier drainage, hydrology and glacier dynamics.
The Cryosphere Discuss., 9, 2013-2052, doi:10.5194/tcd-9-2013-2015, 2015
Impact of model developments on present and future simulations of permafrost in a global land-surface model
Summary: In this paper we use a global land-surface model to study the dynamics of Arctic permafrost. We examine the impact of new and improved processes in the model, namely soil depth and resolution, organic soils, moss and the representation of snow. These improvements make the simulated soil temperatures and thaw depth significantly more realistic. Simulations under future climate scenarios show that permafrost thaws more slowly in the new model version, but still a large amount is lost by 2100.
The Cryosphere Discuss., 9, 1965-2012, doi:10.5194/tcd-9-1965-2015, 2015
First Sentinel-1 detections of avalanche debris
Summary: During an avalanche cycle in January 2015 in northern Norway we used repeat pass Sentinel-1 images to map avalanches. Avalanche debris shows up as increased backscatter in repeat pass images. We detected 489 avalanches in a single scene. Results were validated using high resolution SAR data and field reconnaissance. The results are very promising, and pave the way for operational avalanche monitoring using SAR. Sentinel-1 grant frequent coverage with high quality to monitor avalanches.
The Cryosphere Discuss., 9, 1943-1963, doi:10.5194/tcd-9-1943-2015, 2015
Century-scale simulations of the response of the West Antarctic Ice Sheet to a warming climate
Summary: We used a high resolution ice sheet model capable of resolving grouding line dynamics (BISICLES) to compute responses of the major West Antarctic ice streams to projections of ocean and atmospheric warming. This is computationally demanding, and although other groups have considered parts of West Antarctica, we think this is the first calculation for the whole region at the sub-kilometer resolution that we show is required.
The Cryosphere Discuss., 9, 1887-1942, doi:10.5194/tcd-9-1887-2015, 2015
Meteorological, elevation, and slope effects on surface hoar formation
Summary: We investigate how various meteorological and terrain factors affect surface hoar formation in complex terrain. We modelled the distribution of three surface hoar layers with a coupled NWP - snow cover model, and verify with field studies. Layers developed in regions and elevation bands with warm moist air, light winds, and cold surfaces. Possible avalanche forecasting applications are discussed.
The Cryosphere Discuss., 9, 1857-1885, doi:10.5194/tcd-9-1857-2015, 2015
Four decades of glacier variations at Muztag Ata (Eastern Pamir): a multi-sensor study including Hexagon KH-9 and Pléiades data
Summary: Investigations of glacier mass-balance and area changes at Muztag 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 based on 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 Discuss., 9, 1811-1856, doi:10.5194/tcd-9-1811-2015, 2015
Diagnostic and model dependent uncertainty of simulated Tibetan permafrost area
Summary: We use a model-ensemble approach for simulating permafrost on the Tibetan Plateau. We identify the uncertainties of across-models (state-of-the-art land surface models) and across-methods (most commonly used methods to define permafrost). We differentiate between uncertainties stemming from climatic driving data or from physical process parameterization, and show how these uncertainties vary seasonally and inter-annually, and how estimates are subject to the definition of permafrost used.
The Cryosphere Discuss., 9, 1769-1810, doi:10.5194/tcd-9-1769-2015, 2015
Exploring the utility of quantitative network design in evaluating Arctic sea-ice thickness sampling strategies
Summary: We present a quantitative network design study of the Arctic sea ice-ocean system. For a demonstration, we evaluate two idealised hypothetical flight transects derived from NASA’s Operation IceBridge airborne ice surveys in terms of their potential to improve ten-day to five-month sea-ice forecasts. Our analysis quantifies the benefits of sampling upstream of the target area and of reducing the sampling uncertainty. It further quantifies the complementarity of combining two flight transects.
The Cryosphere Discuss., 9, 1735-1768, doi:10.5194/tcd-9-1735-2015, 2015
Comparing ice discharge through West Antarctic Gateways: Weddell vs. Amundsen Sea warming
Summary: Numerical ice sheet modelling shows that idealized, step-function type ocean warming in the Weddell Sea, where the ice sheet is close to floatation, leads to more immediate ice discharge with a higher sensitivity to small warming levels than the same warming in the Amundsen Sea. While the cumulative ice loss in the Amundsen Sea Sector is of similar magnitude after five centuries of continued warming, ice loss increases at a slower pace and only for significantly higher warming levels.
The Cryosphere Discuss., 9, 1705-1733, doi:10.5194/tcd-9-1705-2015, 2015
Area, elevation and mass changes of the two southernmost ice caps of the Canadian Arctic Archipelago between 1952 and 2014
Summary: In this study, we used multiple datasets, in particular some Pléiades stereo-pairs, to measure the first historical and recent mass balances of Grinnell and Terra Nivea ice caps, as well as area and elevation changes for both ice caps. Results show that rates of area, elevation and mass changes strongly accelerated in the last years. At -1.68 ± 0.36 m a-1 w.e. between 2007 and 2014, Terra Nivea mass balance is among the most negative multi-annual glacier-wide mass balances measured to date.
The Cryosphere Discuss., 9, 1667-1704, doi:10.5194/tcd-9-1667-2015, 2015
Automatic monitoring of the effective thermal conductivity of snow in a low Arctic shrub tundra
Summary: The thermal conductivity of Arctic snow strongly impacts ground temperature, nutrient recycling and vegetation growth. We have monitored the thermal conductivity of snow in low Arctic shrub tundra for 2 consecutive winters using heated needle probes. We observe very different thermal conductivity evolutions in both winters studied, with more extensive melting in the second winter. Results illustrate the effect of vegetation on snow properties and the need to include it in snow physics models.
The Cryosphere Discuss., 9, 1633-1665, doi:10.5194/tcd-9-1633-2015, 2015
Evolution of ice-shelf channels in Antarctic ice shelves
Summary: Floating ice shelves extend the continental ice of Antarctica seawards and mediate ice—ocean interactions. Ice-shelf channels are carved into ice shelves by enhanced channelized melting. With data and modelling we illustrate how the channel geometry changes as a function of basal melt and along-flow advection, when channels are not freely floating, and how channel formation imprints the general flow pattern. This important for quantifying the channel formation from surface velocities only.
The Cryosphere Discuss., 9, 1603-1631, doi:10.5194/tcd-9-1603-2015, 2015
Brief Communication: Getting Greenland's glaciers right – a new dataset of all official Greenlandic glacier names
Summary: During the last centuries hundreds of glaciers in Greenland have been mapped and named. Here we present the official database of all Greenlandic glacier names -consisting of 733 glacier names that have been approved by the Greenlandic authorities. This dataset will help the reseachers working with Greenlandic glaciers in naming the glaciers properly in order to avoid future misunderstandings - as well as help the researcher who is looking for older Glacier names found in the historic literature.
The Cryosphere Discuss., 9, 1593-1601, doi:10.5194/tcd-9-1593-2015, 2015
Satellite monitoring of glaciers in the Karakoram from 1977 to 2013: an overall almost stable population of dynamic glaciers
The Cryosphere Discuss., 9, 1555-1592, doi:10.5194/tcd-9-1555-2015, 2015
A macroscale mixture theory analysis of deposition and sublimation rates during heat and mass transfer in snow
Summary: We implement a continuum mixture theory to elucidate coupled heat and mass transfer phenomena occurring in a snow cover. The effects of mass transfer near the ground, near the surface including diurnal temperature effects, as well as adjacent to an ice crust are examined. The analysis requires an accurate assessment of thermal conductivity and the mass diffusion coefficient for snow. An analytical model for these parameters is developed, showing remarkable agreement with numerical models.
The Cryosphere Discuss., 9, 1503-1554, doi:10.5194/tcd-9-1503-2015, 2015
Assimilation of Antarctic velocity observations provides evidence for uncharted pinning points
Summary: We present a comprehensive, high-resolution assimilation of Antarctic surface velocities with a flow model. The inferred velocities are in very good agreement with observations, even when compared to recent studies on individual shelves. This quality allows to identify a pattern in the velocity mismatch that points at pinning points, not present in the input geometry. We identify 7 potential pinning points around Antarctica, for now uncharted, providing prominent resistance to the ice flow.
The Cryosphere Discuss., 9, 1461-1502, doi:10.5194/tcd-9-1461-2015, 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 Discuss., 9, 1425-1460, doi:10.5194/tcd-9-1425-2015, 2015
SeaRISE experiment revisited: sources of spread in multi-model projections of the Greenland ice-sheet
Summary: This article, as the title denotes, is a follow-up study of an ice-sheet intercomparison project SeaRISE, which focuses on the response of Greenland ice-sheet to future global warming. The projections of the different SeaRISE participants show diversion, which has not been examined in detail to date. This study detects the main sources of the diversion by a number of sensitivity experiments and shows the importance of initialization methods as well as climate forcing methods.
The Cryosphere Discuss., 9, 1383-1424, doi:10.5194/tcd-9-1383-2015, 2015
Albedo reduction caused by black carbon and dust accumulation: a quantitive model applied to the western margin of the Greenland ice sheet
The Cryosphere Discuss., 9, 1345-1381, doi:10.5194/tcd-9-1345-2015, 2015
Quantifying the resolution level where the GRACE satellites can separate Greenland's glacial mass balance from surface mass balance
Summary: Separating surface mass balance from glacial mass balance over Greenland would provide important climatological information and constraints for models, but due to poor spatial resolution, the GRACE gravity satellites cannot ordinarily accomplish this. We demonstrate a least-squares technique which allows us to do so, in theory. However we also find that the GRACE errors are too large to make it practical for real-world use at this time. About a 9-fold reduction in noise would be needed.
The Cryosphere Discuss., 9, 1315-1343, doi:10.5194/tcd-9-1315-2015, 2015
Satellite passive microwave measurements of sea ice concentration: an optimal algorithm and challenges
Summary: An optimal approach is suggested to retrieve sea ice concentration globally for climate monitoring purposes. This is a result of a validation and inter-comparison experiment with thirty satellite passive microwave algorithms (13 shown to demonstrate the findings) where their skills are evaluated over low and high sea ice concentrations, thin ice and areas covered by melt ponds. In addition, atmospheric correction of input brightness temperatures and dynamic tie-points approach are suggested.
The Cryosphere Discuss., 9, 1269-1313, doi:10.5194/tcd-9-1269-2015, 2015
Soot on snow experiments: light-absorbing impurities effect on the natural snowpack
Summary: Soot's (including black carbon and organics) negative effect on a natural snow pack is experimentally addressed in this paper through a series of experiments. Soot concentrations in the snow in the range of 200-200 000 ppb verify the negative effects on the albedo, the physical snow characteristics, as well as increasing the melt rate of the snow pack. Our experimental data generally agrees when compared with the Snow, Ice and Aerosol Radiation model.
The Cryosphere Discuss., 9, 1227-1267, doi:10.5194/tcd-9-1227-2015, 2015
Brief Communication: Future avenues for permafrost science from the perspective of early career researchers
Summary: This is a contribution about the future of permafrost research to the 3rd International Conference on Arctic Research Planning 2015 (ICARP III). We summarize the top five research questions for the next decade of permafrost science from the perspective of early career researchers (ECR). We highlight the pathways and structural preconditions to address these research priorities. This manuscript is an outcome of a community consultation conducted for and by ECR on a global level.
The Cryosphere Discuss., 9, 1209-1225, doi:10.5194/tcd-9-1209-2015, 2015
Summer snowfall on the Greenland Ice Sheet: a study with the updated regional climate model RACMO2.3
Summary: We compare Greenland ice sheet surface mass balance (SMB) from the updated polar version of the regional climate model RACMO2.3 and the previous version 2.1. RACMO2.3 has an adjusted rainfall-to-snowfall conversion favouring summer snowfall over rainfall. Enhanced summer snowfall reduce melt rates in the ablation zone by covering dark ice with highly reflective fresh snow. This improves the modelled SMB-elevation gradient and surface energy balance compared to observations in west Greenland.
The Cryosphere Discuss., 9, 1177-1208, doi:10.5194/tcd-9-1177-2015, 2015
The impact of Saharan dust and black carbon on albedo and long-term glacier mass balance
Summary: Light-absorbing impurities in snow and ice increase the absorption of solar radiation and thus enhance melting. We investigated the effect of Saharan dust and black carbon on the mass balance of an Alpine glacier over 1914-2014. Snow impurities increased melt by 15-19% depending on the location on the glacier. From the accumulation area towards the equilibrium line, the effect of impurities increased as more frequent years with negative mass balance led to a re-exposure of dust-enriched layers.
The Cryosphere Discuss., 9, 1133-1175, doi:10.5194/tcd-9-1133-2015, 2015
Arctic sea ice area in CMIP3 and CMIP5 climate model ensembles – variability and change
Summary: The shrinking Arctic sea ice cover is probably the clearest manifestation of ongoing climate change. The last generation of climate models from World Climate Research Programme Coupled Model Intercomparison Project (CMIP3 and CMIP5) simulate consistent changes in the Sea Ice Area (SIA) seasonal cycle. On average, the sensitivity of SIA to external forcing is enhanced in the CMIP5 models. The Arctic SIA variability response to anthropogenic forcing is different in CMIP3 and CMIP5.
The Cryosphere Discuss., 9, 1077-1131, doi:10.5194/tcd-9-1077-2015, 2015
Microscale variability of snow depth using U.A.S. technology
Summary: We investigate the capabilities of photogrammetry-based surveys with Unmanned Aerial Systems (U.A.S.) to retrieve the snow depth distribution at cm resolution over a small alpine area. Results show that the U.A.S. technique provides an accurate estimation of point snow depth values, and a distributed evaluation of the snow accumulation patterns.
The Cryosphere Discuss., 9, 1047-1075, doi:10.5194/tcd-9-1047-2015, 2015
Tomography-based monitoring of isothermal snow metamorphism under advective conditions
The Cryosphere Discuss., 9, 1021-1045, doi:10.5194/tcd-9-1021-2015, 2015
Cloud effects on the surface energy and mass balance of Brewster Glacier, New Zealand
Summary: Clouds are shown to force a fundamental change in the surface energy and mass balance of Brewster Glacier, New Zealand. Greater melt during cloudy periods was associated with enhanced emission of longwave radiation by clouds and increased atmospheric vapour pressure, rather than a minimal change in mean air temperature and wind speed. Surface mass balance was more sensitive to changes in air temperature during cloudy periods due to more frequent melt and a strong precipitation – albedo feedback.
The Cryosphere Discuss., 9, 975-1019, doi:10.5194/tcd-9-975-2015, 2015
Estimation and calibration of the water isotope differential diffusion length in ice core records
Summary: The diffusion of the stable water isotope signal during firnification of snow is a temperature dependent process. Therefore, past local temperatures can be derived from the differential diffusion length. In this paper we develop a new method for determining this quantity and compare it with the existing method. Both methods are applied to a large number of synthetic data sets to assess the precision and accuracy of the reconstruction and to a section of the Antarctic EDML ice core record.
The Cryosphere Discuss., 9, 927-973, doi:10.5194/tcd-9-927-2015, 2015
Parameterization of single-scattering properties of snow
Summary: While snow grains are distinctly non-spherical, spheres are often assumed in radiative transfer calculations. Here, angular scattering measurements for blowing snow are used to select an optically equivalent snow grain shape model. Parameterizations are then developed for the asymmetry parameter, single-scattering co-albedo and phase function of snow. The parameterizations will help to improve the treatment of snow in radiative transfer applications, including remote sensing and climate models.
The Cryosphere Discuss., 9, 873-926, doi:10.5194/tcd-9-873-2015, 2015
Brief Communication: Newly developing rift in Larsen C Ice Shelf presents significant risk to stability
Summary: Within the last year, a large rift in the southern part of the Larsen C Ice Shelf, Antarctic Peninsula, propagated towards the inner part of the ice shelf. In this study we present the development of the rift as derived from remote sensing data and assess the impact of possible calving scenarios on the future stability of the Larsen C Ice Shelf, using a numerical model. We find that the calving front is likely to become unstable after the anticipated calving events.
The Cryosphere Discuss., 9, 861-872, doi:10.5194/tcd-9-861-2015, 2015
Constraints on the δ2H diffusion rate in firn from field measurements at Summit, Greenland
Summary: We performed 2H isotope diffusion measurements in the upper 3 meters of firn at Summit, Greenland, by following over a four years period isotope-enriched snow that we deposited. We found that the diffusion process was much less rapid than in the mostly used model. We discuss several aspects of the diffusion process that are still poorly constrained and might lead to this discrepancy. Quantitative knowledge of diffusion is necessary for use of the diffusion process itself as a climate proxy.
The Cryosphere Discuss., 9, 817-859, doi:10.5194/tcd-9-817-2015, 2015
User requirements for the snow and land ice services – CryoLand
Summary: The paper provides detailed information on the outcome of a user survey carried out in the EU FP7 project CryoLand. The project focuses on monitoring of seasonal snow, glaciers and lake/river ice. The user survey showed that a European operational snow and land ice service is required and that there exists products that can meet the specific needs. The majority of the users were mainly interested in the snow services, but also the lake/river ice products and the glacier products were desired.
The Cryosphere Discuss., 9, 791-816, doi:10.5194/tcd-9-791-2015, 2015
A ground temperature map of the North Atlantic permafrost region based on remote sensing and reanalysis data
Summary: We use remotely sensed land surface temperature and land cover in conjunction with air temperature and snowfall from a reanalysis product as input for a simple permafrost model. The scheme is applied to the permafrost regions bordering the N Atlantic. A comparison with ground temperatures in boreholes suggests a modeling accuracy of 2 to 2.5 °C.
The Cryosphere Discuss., 9, 753-790, doi:10.5194/tcd-9-753-2015, 2015
Response of the large-scale subglacial drainage system of North East Greenland to surface elevation changes
The Cryosphere Discuss., 9, 719-751, doi:10.5194/tcd-9-719-2015, 2015
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.
The Cryosphere Discuss., 9, 655-717, doi:10.5194/tcd-9-655-2015, 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 Discuss., 9, 609-653, doi:10.5194/tcd-9-609-2015, 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.
The Cryosphere Discuss., 9, 541-565, doi:10.5194/tcd-9-541-2015, 2015
Winter observations of CO2 exchange between sea-ice and the atmosphere in a coastal fjord environment
The Cryosphere Discuss., 9, 45-75, doi:10.5194/tcd-9-45-2015, 2015
Surface speed and frontal ablation of Kronebreen and Kongsbreen, NW-Svalbard, from SAR offset tracking
The Cryosphere Discuss., 8, 6193-6233, doi:10.5194/tcd-8-6193-2014, 2014
Role of rainwater induced subsurface flow in water-level dynamics and thermoerosion of shallow thermokarst ponds on the Northeastern Qinghai–Tibet Plateau
The Cryosphere Discuss., 8, 6117-6146, doi:10.5194/tcd-8-6117-2014, 2014