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, 9, 1895-1913, doi:10.5194/tc-9-1895-2015, 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, the mean monthly air temperature exceeds a value between -15°C and -10°C, depending on the region, albedo decreases with an increase of the temperature. The complexity of processes involved in surface albedo changes is discussed.
The Cryosphere, 9, 1879-1893, doi:10.5194/tc-9-1879-2015, 2015
A macroscale mixture theory analysis of deposition and sublimation rates during heat and mass transfer in dry 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, 9, 1857-1878, doi:10.5194/tc-9-1857-2015, 2015
Ice sheet mass loss caused by dust and black carbon accumulation
Summary: Soot (black carbon) and dust particles darken the surface of ice sheets and glaciers as they accumulate. This causes more ice to melt, which releases more particles from within the ice. This positive feedback mechanism is studied with a new two-dimensional model, mimicking the conditions of Greenland, under different climate warming scenarios. In the warmest scenario, the additional ice sheet mass loss until the year 3000 is up to 7%.
The Cryosphere, 9, 1845-1856, doi:10.5194/tc-9-1845-2015, 2015
Evaluation of the updated regional climate model RACMO2.3: summer snowfall impact on the Greenland Ice Sheet
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, 9, 1831-1844, doi:10.5194/tc-9-1831-2015, 2015
Thermal energy in dry snow avalanches
Summary: Infrared radiation thermography (IRT) was used to assess the surface temperature of avalanches with high spatial resolution. Thermal energy increase due to friction was mainly depending on the elevation drop of the avalanche. Warming due to entrainment was very specific to the individual avalanche and depends on the temperature of the snow along the path and the erosion depth. The warmest temperatures were located in the deposits of the dense core.
The Cryosphere, 9, 1819-1830, doi:10.5194/tc-9-1819-2015, 2015
Inter-comparison and evaluation of sea ice algorithms: towards further identification of challenges and optimal approach using passive microwave observations
Summary: Thirty sea ice algorithms are inter-compared and evaluated systematically over low and high sea ice concentrations, as well as in the presence of thin ice and melt ponds. A hybrid approach is suggested to retrieve sea ice concentration globally for climate monitoring purposes. This approach consists of a combination of two algorithms plus the implementation of a dynamic tie point and atmospheric correction of input brightness temperatures.
The Cryosphere, 9, 1797-1817, doi:10.5194/tc-9-1797-2015, 2015
Evolution of Ossoue Glacier (French Pyrenees) since the end of the Little Ice Age
Summary: Pyrenean glaciers are currently the southernmost glaciers in Europe. Using an exceptional archive of historical data sets and recent accurate observations, we propose the reconstruction of the length, area, elevation, and mass balance of Ossoue Glacier (French Pyrenees) since the Little Ice Age. We show that its evolution is in good agreement with climatic data. Assuming that the current ablation rate stays constant, Ossoue Glacier will disappear midway through the 21st century.
The Cryosphere, 9, 1773-1795, doi:10.5194/tc-9-1773-2015, 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, 9, 1761-1772, doi:10.5194/tc-9-1761-2015, 2015
Improving semi-automated glacier mapping with a multi-method approach: applications in central Asia
Summary: We describe and apply a newly developed glacial mapping algorithm which uses spectral, topographic, velocity, and spatial data to quickly and accurately map glacial extents over a wide area. This method maps both clean glacier ice and debris-covered glacier tongues across diverse topographic, land cover, and spectral settings using primarily open-source tools.
The Cryosphere, 9, 1747-1759, doi:10.5194/tc-9-1747-2015, 2015
Improving Arctic sea ice edge forecasts by assimilating high horizontal resolution sea ice concentration data into the US Navy's ice forecast systems
Summary: This study presents the improvement in the US Navy's operational sea ice forecast systems gained by assimilating high horizontal resolution satellite-derived ice concentration products. A method of blending ice concentration observations from AMSR2 along with a sea ice mask has been developed, resulting in an ice concentration product with high spatial resolution. A significant improvement in the ice edge location has been shown in the operational system assimilating this new product.
The Cryosphere, 9, 1735-1745, doi:10.5194/tc-9-1735-2015, 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 10-day to 5-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, 9, 1721-1733, doi:10.5194/tc-9-1721-2015, 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 (ECRs). 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 ECRs on a global level.
The Cryosphere, 9, 1715-1720, doi:10.5194/tc-9-1715-2015, 2015
Winter observations of CO2 exchange between sea ice and the atmosphere in a coastal fjord environment
The Cryosphere, 9, 1701-1713, doi:10.5194/tc-9-1701-2015, 2015
Black carbon in snow in the upper Himalayan Khumbu Valley, Nepal: observations and modeling of the impact on snow albedo, melting, and radiative forcing
Summary: We detected up to 70 ppb of black carbon (BC) in surface snow in the upper Khumbu Valley, Nepal. With an upgraded snowpack model, including radiative transfer inside the snow, we studied the impact of BC on snow albedo, melting and radiative forcing for the sensitive high altitude regions of the Himalayas. We found that due to BC, the melting of the snow can be shifted by several days up to several weeks depending on meteorological conditions. The impact of BC is larger in dirty snow.
The Cryosphere, 9, 1685-1699, doi:10.5194/tc-9-1685-2015, 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, 9, 1663-1683, doi:10.5194/tc-9-1663-2015, 2015
Temporal variations in the flow of a large Antarctic ice stream controlled by tidally induced changes in the subglacial water system
Summary: We use a full-Stokes model to investigate the long period modulation of Rutford Ice Stream flow by the ocean tide. We find that using a nonlinear sliding law cannot fully explain the measurements and an additional mechanism, whereby tidally induced subglacial pressure variations are transmitted upstream from the grounding line, is also required to match the large amplitude and decay length scale of the observations.
The Cryosphere, 9, 1649-1661, doi:10.5194/tc-9-1649-2015, 2015
Retrieving the 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.
The Cryosphere, 9, 1633-1648, doi:10.5194/tc-9-1633-2015, 2015
Impact of debris cover on glacier ablation and atmosphere–glacier feedbacks in the Karakoram
Summary: We investigate the impact of surface debris on glacier energy and mass fluxes and on atmosphere-glacier feedbacks in the Karakoram range, by including debris in an interactively coupled atmosphere-glacier model. The model is run from 1 May to 1 October 2004, with a simple specification of debris thickness. We find an appreciable reduction in ablation that exceeds 5m w.e. on glacier tongues, as well as significant alterations to near-surface air temperatures and boundary layer dynamics.
The Cryosphere, 9, 1617-1632, doi:10.5194/tc-9-1617-2015, 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, 9, 1601-1616, doi:10.5194/tc-9-1601-2015, 2015