Intercomparison of snow density measurements: bias, precision and spatial resolution
Summary: Density is a fundamental property of porous media such as snow. During the MicroSnow Davos 2014 workshop different approaches (box, wedge and cylinder type density cutters, micro computed tomography) to measure snow density were applied in a controlled laboratory environment and in the field. In general, result suggests that snow densities measured by different methods agree within 9%. However, the density profiles resolved by the measurement methods differed considerably.
The Cryosphere Discuss., 9, 3581-3616, doi:10.5194/tcd-9-3581-2015, 2015
Elevation change of the Greenland ice sheet due to surface mass balance and firn processes, 1960–2013
The Cryosphere Discuss., 9, 3541-3580, doi:10.5194/tcd-9-3541-2015, 2015
Debris-covered energy balance model for Imja-Lhotse Shar Glacier in the Everest region of Nepal
Summary: A debris-covered energy balance was used to model debris temperatures and sub-debris ablation rates on Imja-Lhotse Shar glacier during the 2014 melt season. Field measurements were used to assess model performance. A novel method was also developed using Structure from Motion to estimate the surface roughness. Lastly, the effects of temporal resolution, i.e., 6h and daily time steps, and various methods for estimating the latent heat flux were also investigated.
The Cryosphere Discuss., 9, 3503-3540, doi:10.5194/tcd-9-3503-2015, 2015
On the substantial influence of the treatment of friction at the grounding line
Summary: In this paper we present three different methods to apply the friction in the very close vicinity of the grounding line and show that the results are very sensitive to the chosen method. Because all previous results using Elmer/Ice were published using only one of these three methods, we here honestly inform the community about the impact of this choice. The new results obtained in this work are made available to the community as Supplementary Materials.
The Cryosphere Discuss., 9, 3475-3501, doi:10.5194/tcd-9-3475-2015, 2015
Measurements and modelling of snow particle size and shortwave infrared albedo over a melting Antarctic ice sheet
Summary: We illustrate a method to measure the size distribution of a snow particle metric from macro-photos of snow particles. This snow particle metric corresponds well to the optically equivalent effective radius. Our results evidence the impact of grain shape on albedo, indicate that more than just one particle metric distribution is needed to characterize the snow scattering properties at all optical wavelengths, and suggest an impact of surface roughness on the shortwave infrared albedo.
The Cryosphere Discuss., 9, 3405-3474, doi:10.5194/tcd-9-3405-2015, 2015
Effect of soil property uncertainties on permafrost thaw projections: a calibration-constrained analysis
Summary: This paper investigates the uncertainty associated with permafrost thaw projections at an intensively monitored site. Permafrost thaw projections are simulated using a thermal hydrology model forced by a worst case scenario carbon emission scenario. The uncertainty associated with active layer depth, saturation state, thermal regime, and thaw duration are quantified and compared with the effects of climate model uncertainty on permafrost thaw projections.
The Cryosphere Discuss., 9, 3351-3404, doi:10.5194/tcd-9-3351-2015, 2015
Snow and albedo climate change impacts across the United States Northern Great Plains
Summary: We used 60 years of daily meteorological data from 20 stations across the United States Northern Great Plains to examine climate trends focusing on the winter climate. Besides standard climate trends, we computed trends in snowfall amounts, days with precipitation, days with snow, and modeled winter albedo (surface reflectivity). Daily minimum temperatures and days with precipitation increased at most locations, while winter albedo decreased at many stations. There was much spatial variability.
The Cryosphere Discuss., 9, 3331-3349, doi:10.5194/tcd-9-3331-2015, 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
The Cryosphere Discuss., 9, 3293-3329, doi:10.5194/tcd-9-3293-2015, 2015
Estimating supraglacial lake depth in western Greenland using Landsat 8 and comparison with other multispectral methods
Summary: Liquid water stored on the surface of ice sheets and glaciers, such as that in surface (supraglacial) lakes, plays a key role in the glacial hydrological system. Multispectral remote sensing can be used to detect lakes and estimate their depth. Here, we use in situ data to assess lake depth retrieval using the recently launched Landsat 8. We validate Landsat 8-derived depths and provide suggestions for future applications. We apply our method to a case study are in Greenland for summer 2014.
The Cryosphere Discuss., 9, 3257-3292, doi:10.5194/tcd-9-3257-2015, 2015
Improving a priori regional climate model estimates of Greenland ice sheet surface mass loss through assimilation of measured ice surface temperatures
Summary: An Ensemble Batch Smoother was used to assess the feasibility of generating a reanalysis estimate of the Greenland Ice sheet (GrIS) surface mass fluxes (SMF) via integrating measured ice surface temperatures with a regional climate model estimate. The results showed that assimilation of IST were able to overcome uncertainties in meteorological forcings that drive the GrIS surface processes. We showed that the proposed methodology is able to generate posterior reanalysis estimates of the SMF.
The Cryosphere Discuss., 9, 3205-3255, doi:10.5194/tcd-9-3205-2015, 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 nonlinearity in balance gradients.
The Cryosphere Discuss., 9, 3165-3204, doi:10.5194/tcd-9-3165-2015, 2015
The importance of a surface organic layer in simulating permafrost thermal and carbon dynamics
The Cryosphere Discuss., 9, 3137-3163, doi:10.5194/tcd-9-3137-2015, 2015
Evaluation of the CMIP5 models in the aim of regional modelling of the Antarctic surface mass balance
Summary: Estimates of the Antarctic surface mass balance with regional climate models (RCMs) require appropriate fields for forcing. Here we evaluate 41 climate models from CMIP5 over Antarctica, including 5 reanalyses in the inter-comparison. ACCESS1-3 seems to be the most pertinent choice for RCM forcing and we show that climate change is much more dependent on the initial state of sea-ice and on the local feedback between air temperature increase and sea-ice decrease than on the global warming signal.
The Cryosphere Discuss., 9, 3113-3136, doi:10.5194/tcd-9-3113-2015, 2015
Soot on snow experiment: bidirectional reflectance factor measurements of contaminated snow
The Cryosphere Discuss., 9, 3075-3111, doi:10.5194/tcd-9-3075-2015, 2015
Photopolarimetric retrievals of snow properties
The Cryosphere Discuss., 9, 3055-3074, doi:10.5194/tcd-9-3055-2015, 2015
ENSO influence on surface energy and mass balance at Shallap Glacier, Cordillera Blanca, Peru
Summary: Using a newly developed open-source tool, we downscale the glacier surface energy and mass balance fluxes at Shallap Glacier. This allows an unprecedented quantification of the ENSO influence on a tropical glacier at climatological time scales (1980-2013). We find a stronger and steadier anti-correlation between pacific sea surface temperature (SST) and glacier mass balance than previously reported and provide keys to understand its mechanism.
The Cryosphere Discuss., 9, 2999-3053, doi:10.5194/tcd-9-2999-2015, 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 Discuss., 9, 2955-2997, doi:10.5194/tcd-9-2955-2015, 2015
The relative contributions of calving and surface ablation to ice loss at a lake-terminating glacier
Summary: Calving and surface melt is estimated for Bridge Glacier, a lake-terminating glacier in British Columbia, Canada. Estimates suggest that calving was a relatively minor contributor of ice loss until the terminus began to float in 1991. Since then, calving has accounted for 10-25% of total ice loss. However, as the glacier retreats into shallower water, and eventually onto dry land, calving losses are expected to decrease, and the glacier is expected to respond more readily to regional climate.
The Cryosphere Discuss., 9, 2915-2953, doi:10.5194/tcd-9-2915-2015, 2015
Changing surface–atmosphere energy exchange and refreezing capacity of the lower accumulation area, west Greenland
The Cryosphere Discuss., 9, 2867-2913, doi:10.5194/tcd-9-2867-2015, 2015
CryoSat-2 delivers monthly and inter-annual surface elevation change for Arctic ice caps
Summary: We show that the Cryosat (CS) radar altimeter can measure elevation change on a variety of Arctic ice caps. With the frequent coverage of Cryosat it is even possible to track summer surface height loss due to extensive melt; no other satellite altimeter has been able to do this. However, we also show that under cold conditions there is a bias between the surface and Cryosat detected elevation which varies with the conditions of the upper snow and firn layers.
The Cryosphere Discuss., 9, 2821-2865, doi:10.5194/tcd-9-2821-2015, 2015
Monitoring ice break-up on the Mackenzie River using MODIS data
Summary: This study involves the analysis of MODIS Level 3 500-m snow products, complemented with 250-m Level 1B data, to monitor ice cover during the break-up period on the Mackenzie River, Canada. Results from the analysis of data for 13 ice seasons (2001-2013) show that first day ice-off dates is observed between days of year (DOY) 115-125 and end DOY 145-155, resulting in average melt durations of about 30-40 days and concluded that MODIS can for monitoring ice break-up.
The Cryosphere Discuss., 9, 2783-2820, doi:10.5194/tcd-9-2783-2015, 2015
Satellite observations of changes in snow-covered land surface albedo during spring in the Northern Hemisphere
Summary: Snow cover explained most of the spring surface albedo changes in the Northern Hemisphere in the years 2000−2012. However, there are vast areas where albedo changed up to ±0.2 under full snow covered conditions. We found that if in these areas mean monthly air temperature exceeds −15°C, albedo decreases with increase of the temperature. Vegetation and precipitation changes affects albedo in Chukotka and Eastern Siberia. Complexity of processes involved into surface albedo changes are discussed.
The Cryosphere Discuss., 9, 2745-2782, doi:10.5194/tcd-9-2745-2015, 2015
Correction of albedo measurements due to unknown geometry
Summary: Diurnal albedo variation of glaciers on clear sky days are high due to geometric effects caused by tilt errors, which are corrected where tilts of sensors and slopes are unknown. With a reference measurement using a horizontally levelled sensor a model is developed and fitted to the measured data to determine tilts and directions which vary daily due to changing atmospheric conditions and snow cover. The results show an under- or overestimation of albedo depending on the direction of the slope.
The Cryosphere Discuss., 9, 2709-2744, doi:10.5194/tcd-9-2709-2015, 2015
Verification of the multi-layer SNOWPACK model with different water transport schemes
Summary: A verification of the physics based SNOWPACK model with field observations showed that typical snowpack properties like density and temperature are adequately simulated. Also two water transport schemes were verified, showing that although Richards equation improves snowpack runoff and several aspects of the internal snowpack structure, the bucket scheme appeared to have a higher agreement with the snow microstructure. The choice of water transport scheme may depend on the intended application.
The Cryosphere Discuss., 9, 2655-2707, doi:10.5194/tcd-9-2655-2015, 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 exercices dedicated to evaluate models' ability to represent coastal changes. Uncertainties in projections can be substantially decreased if a selection of models is made and unqualified models for coastal dynamics representation are excluded.
The Cryosphere Discuss., 9, 2625-2654, doi:10.5194/tcd-9-2625-2015, 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
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
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
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