A new spatially and temporally variable sigma parameter in degree-day melt modelling of the Greenland Ice Sheet 1870–2013
The Cryosphere Discuss., 9, 5327-5371, doi:10.5194/tcd-9-5327-2015, 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
Tremor during ice stream stick-slip
The Cryosphere Discuss., 9, 5253-5289, doi:10.5194/tcd-9-5253-2015, 2015
Imaging air volume fraction in sea ice using non-destructive X-ray tomography
Summary: We present a new non-destructive X-ray computed tomography technique to quantify the air volume fraction and produce separate 3-D images of air-volume inclusions in sea ice.While the internal layers showed air-volume fractions <2%, the ice-air interface (top 2 cm) showed values up to 5% .As a result of the presence of large bubbles and higher air volume fraction measurements in sea ice we introduce new perspectives on processes regulating gas exchange at the ice-atmosphere interface.
The Cryosphere Discuss., 9, 5203-5251, doi:10.5194/tcd-9-5203-2015, 2015
Recent summer sea ice thickness surveys in the Fram Strait and associated volume fluxes
Summary: We present an extensive data set of ground-based and airborne electromagnetic ice thickness measurements covering Fram Strait in summer between 2001 and 2012. An investigation of back trajectories of surveyed sea ice using satellite based sea ice motion data allows us to examine the connection between thickness variability, ice age and source area. In addition, we determine across and along Strait gradients in ice thickness and associated volume fluxes.
The Cryosphere Discuss., 9, 5171-5202, doi:10.5194/tcd-9-5171-2015, 2015
Radiative transfer model for contaminated slabs: experimental validations
Summary: This article presents a set of spectro-goniometric measurements of different water ice samples and their comparison with an approximated radiative transfer model using a Bayesian approach. Two kinds of experiments were conducted: the specular spot was investigated, and then the diffuse radiation. We show that the approximated model is able to satisfactorily reproduce the spectro-radiogoniometric data, and that the inverted parameters are compatible with independent measurements.
The Cryosphere Discuss., 9, 5137-5169, doi:10.5194/tcd-9-5137-2015, 2015
The modelled surface mass balance of the Antarctic Peninsula at 5.5 km horizontal resolution
Summary: This study presents the first high-resolution (5.5 km) modelled estimate of Surface Mass Balance (SMB) over the period 1979-2014 for the Antarctic Peninsula (AP). Precipitation (snowfall and rain) largely determines the SMB, and is exceptionally high over the western mountain slopes, with annual values >4 m water equivalent. Snowmelt is widespread over the AP, but only runs off into the ocean at some locations: the Larsen B,C, and Wilkins ice shelves, and along the northwestern mountains.
The Cryosphere Discuss., 9, 5097-5136, doi:10.5194/tcd-9-5097-2015, 2015
A synthetic ice core approach to estimate ion relocation in an ice field site experiencing periodical melt; a case study on Lomonosovfonna, Svalbard
The Cryosphere Discuss., 9, 5053-5095, doi:10.5194/tcd-9-5053-2015, 2015
Accelerated wastage of the Monte Perdido Glacier in the Spanish Pyrenees during recent stationary climatic conditions
The Cryosphere Discuss., 9, 5021-5051, doi:10.5194/tcd-9-5021-2015, 2015
Estimating spatial distribution of daily snow depth with kriging methods: combination of MODIS snow cover area data and ground-based observations
Summary: An integrated framework was developed for estimating spatial distribution of snow depth. Four types of kriging methods were compared and evaluated: OK, UK, OCK, UCK. MODIS SCA data were used to compensate for the scarcity and uneven distribution of stations Results from the paper showed snow depth could be improved by the proposed method.
The Cryosphere Discuss., 9, 4997-5020, doi:10.5194/tcd-9-4997-2015, 2015
Brief Communication: Upper air relaxation in RACMO2 significantly improves modelled interannual SMB variability in Antarctica
Summary: Regional Climate Models improve the spatial surface mass balance (SMB) patterns in Antarctica compared to reanalyzes, but deteriorate the representation of interannual variability in SMB. Hence, we implemented additional nudging in our Regional Climate Model RACMO2. Using annual SMB observations of the Twaites drainage basin, Antarctica, we show that this nudging vastly improves the representation of interannual variability without significant deterioration of the modeled mean SMB fields.
The Cryosphere Discuss., 9, 4981-4995, doi:10.5194/tcd-9-4981-2015, 2015
Reconstructing glacier mass balances in the Central Andes of Chile and Argentina using local and regional hydro-climatic data
Summary: Glaciar Echaurren Norte (ECH, 34°S) has the longest (>35 yrs) mass balance record in South America. A minimal model that explains 78% of the variance in the ECH annual record identifies precipitation as the most important forcing. A regional streamflow series allows extending the ECH annual record back to 1909, with a cumulated ice loss of -42 m.w.eq. Similarities with documented glacier advances and other shorter mass balance series suggest the ECH reconstruction is regionally representative.
The Cryosphere Discuss., 9, 4949-4980, doi:10.5194/tcd-9-4949-2015, 2015
Time forecast of a break-off event from a hanging glacier
Summary: The break-off of a cold hanging glacier could be successfully predicted 10 days in advance thanks to very accurate surface displacement measurements taken right up to the final event. This break-off event also confirmed that surface displacements experience a power law acceleration along with superimposed log-periodic oscillations prior to the final rupture. This paper describes the methods used to achieve a satisfactory time forecast in real time.
The Cryosphere Discuss., 9, 4925-4948, doi:10.5194/tcd-9-4925-2015, 2015
About the consistency between Envisat and CryoSat-2 radar freeboard retrieval over Antarctic sea ice
Summary: The comparison between CryoSat-2 and Envisat radar freeboard over Antarctic sea ice revealed a good agreement with adequate freeboard distributions and sensor differences mostly below 0.1m for modal and even less for mean freeboard over winter months. Regions with perennial sea ice and along the coasts show the highest differences. The impact of those differences on the total Antarctic sea ice volume is estimated to be within few percent.
The Cryosphere Discuss., 9, 4893-4923, doi:10.5194/tcd-9-4893-2015, 2015
Glacier dynamics over the last quarter of a century at Jakobshavn Isbræ
Summary: We use a 3-D glacier model to simulate the behaviour of Jakobshavn Isbræ. We identify 3 major accelerations in 1998, 2003, and 2012. Our analysis suggests that the 2012 acceleration is likely the result of an exceptionally long melt season dominated by extreme melt events. As opposed to other regions on the Greenland ice sheet, where dynamically induced mass loss has slowed down over recent years, both modelled and observed results for JI suggest a continuation of the acceleration in mass loss.
The Cryosphere Discuss., 9, 4865-4892, doi:10.5194/tcd-9-4865-2015, 2015
Tomography-based observation of sublimation and snow metamorphism under temperature gradient and advective flow
Summary: The exothermic gas-to-solid phase change is favorable vis-a-vis the endothermic solid-to-gas phase change, thus leading to more ice deposition than ice sublimation. Sublimation has a marked effect on the structural change of the ice matrix but diffusion of water vapor in the direction of the temperature gradient counteracted the mass transport of advection. Therefore, the total net ice change was negligible but the strong reposition process is relevant for atmospheric chemistry.
The Cryosphere Discuss., 9, 4845-4864, doi:10.5194/tcd-9-4845-2015, 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
Geodetic mass balance record with rigorous uncertainty estimates deduced from aerial photographs and LiDAR data – case study from Drangajökull ice cap, NW-Iceland
The Cryosphere Discuss., 9, 4733-4785, doi:10.5194/tcd-9-4733-2015, 2015
Virtual radar ice buoys – a method for measuring fine-scale dynamic properties of sea ice
Summary: We present an algorithm for continuous ice dynamics estimation based on coastal and ship radar data. The ice dynamics are estimated based on automatically selected ice targets (virtual buoys, VB's) and an optical flow algorithm. VB's are added when necessary. We show some examples of the tracking and quantities derived from the VB motion.
The Cryosphere Discuss., 9, 4701-4731, doi:10.5194/tcd-9-4701-2015, 2015
Improved GRACE regional mass balance estimates of the Greenland Ice Sheet cross-validated with the input-output method
The Cryosphere Discuss., 9, 4661-4699, doi:10.5194/tcd-9-4661-2015, 2015
Extraordinary runoff from the Greenland Ice Sheet in 2012 amplified by hypsometry and depleted firn-retention
The Cryosphere Discuss., 9, 4625-4660, doi:10.5194/tcd-9-4625-2015, 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
Late summer sea ice segmentation with multi-polarisation SAR features in C- and X-band
Summary: This paper demonstrates how sea ice segmentation using high-resolution multi-polarisation synthetic aperture radar (SAR) can be used to retrieve valuable information about sea ice type during late summer. It add knowledge to how choice of SAR features influence the information gain, and highlights the sea ice segmentation capability of both C and X-band in late summer. The study contributes to an increased understanding of sea ice mapping and monitoring with SAR in the melt season.
The Cryosphere Discuss., 9, 4539-4581, doi:10.5194/tcd-9-4539-2015, 2015
Summertime evolution of snow specific surface area close to the surface on the Antarctic Plateau
Summary: The albedo and surface energy budget of the Antarctic Plateau are largely determined by snow specific surface area. The latter experiences substantial daily-to-seasonal variations in response to meteorological conditions. In particular, it decreases by a factor three in summer, causing a drop in albedo. These variations are monitored from in situ and remote sensing observations at Dome C. For the first time, they are also simulated with a snowpack evolution model adapted to Antarctic conditions.
The Cryosphere Discuss., 9, 4499-4538, doi:10.5194/tcd-9-4499-2015, 2015
Committed near-future retreat of Smith, Pope, and Kohler Glaciers inferred by transient model calibration
Summary: We calibrate a time-dependent ice model through optimal fit to transient observations of surface elevation and velocity, a novel procedure in glaciology and in particular for an ice stream with a dynamic grounding line. We show this procedure gives a level of confidence in model projections that cannot be achieved through more commonly used glaciological data assimilation methods. We show that Smith Glacier is in a state of retreat regardless of climatic forcing for the next several decades.
The Cryosphere Discuss., 9, 4459-4498, doi:10.5194/tcd-9-4459-2015, 2015
The electrical self-potential method is a non-intrusive snow-hydrological sensor
Summary: We demonstrate for the first time that the electrical self-potential geophysical technique can sense in-situ bulk meltwater fluxes that cannot readily be measured using existing techniques. The work facilitates continuous temporal measurement on spatial scales that match those used on operational snow models. Together with in-situ trialling and testing the new theory and numerical model has broad and immediate implications for snow measurement practice, modelling and operational snow forecasting
The Cryosphere Discuss., 9, 4437-4457, doi:10.5194/tcd-9-4437-2015, 2015
Halogen-based reconstruction of Russian Arctic sea ice area from the Akademii Nauk ice core (Severnaya Zemlya)
Summary: The role of sea ice in the Earth climate system is still under debate, although it is known to influence albedo, ocean circulation, and atmosphere-ocean heat and gas exchange. Here we present a reconstruction of AD 1950 to 1998 sea ice in the Laptev Sea based on the Akademii Nauk ice core (Severnaya Zemlya, Russian Arctic) and Halogens measurements. The results suggest a connection between Brexc and spring sea ice, as well as a connection between iodine concentration and summer sea ice.
The Cryosphere Discuss., 9, 4407-4436, doi:10.5194/tcd-9-4407-2015, 2015
Orographic and vegetation effects on snow accumulation in the southern Sierra Nevada: a statistical summary from LiDAR data
Summary: By analyzing high resolution LiDAR products, we quantified the snow depth dependency on elevation, slope, aspect of the terrain and also the surrounding vegetation in four catchment size sites in the southern Sierra Nevada during snow peak season. The results reveals that snow depth increases with elevation, and more likely to have more accumulation on flat and northerly faced slopes. Also, surrounding vegetation shallows the snowpack in canopy gaps. These features are consistent across sites.
The Cryosphere Discuss., 9, 4377-4405, doi:10.5194/tcd-9-4377-2015, 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
Sheet, stream, and shelf flow as progressive ice-bed uncoupling: Byrd Glacier, Antarctica, and Jakobshavn Isbrae, Greenland
The Cryosphere Discuss., 9, 4271-4354, doi:10.5194/tcd-9-4271-2015, 2015
A moving point approach to model shallow ice sheets: a study case with radially-symmetrical ice sheets
Summary: This paper introduce a moving point approach to model the flow of ice sheets. This particular moving grid numerical approach is based on the conservation of local masses. This allows the ice sheet margins to be tracked explicitly. A finite difference moving point scheme is derived and applied in a simplified context (1D). The conservation method is also suitable for 2D-scenarios. This paper is a first step towards applications of the conservation method to realistic 2D-cases.
The Cryosphere Discuss., 9, 4237-4270, doi:10.5194/tcd-9-4237-2015, 2015
Numerical simulations of the Cordilleran ice sheet through the last glacial cycle
Summary: We use a numerical model based on approximated ice flow physics and calibrated against field-based evidence to present numerical simulations of multiple advance and retreat phases of the former Cordilleran Ice Sheet in North America during the last glacial cycle (120 000 -- 0 years before present).
The Cryosphere Discuss., 9, 4147-4203, doi:10.5194/tcd-9-4147-2015, 2015
Utilisation of CryoSat-2 SAR altimeter in operational ice charting
Summary: This paper demonstrates the use of the Cryosat-2 SAR altimeter in operational ice charting. We take Cryosat-2 data and compare that to ice charts over the sea ice covered regions in Barents-and Kara seas. We also present an automatic classification method for Cryosat-2 measurements that could be used support for navigation. We conclude that SAR altimeter measurements can be valuable to operational ice charting if other data sources are unavailable.
The Cryosphere Discuss., 9, 4117-4145, doi:10.5194/tcd-9-4117-2015, 2015
Observations of seasonal and diurnal glacier velocities at Mount Rainier, Washington using terrestrial radar interferometry
Summary: Terrestrial radar interferometry measurements allow us to capture the entire velocity field of several alpine glaciers at Mount Rainier, WA and investigate glacier dynamics. We analyze spatial patterns and compare repeat measurements to investigate diurnal and seasonal glacier changes. We find no significant diurnal variability but a very large seasonal slowdown (25 to 50 %) from July to November likely due to changes in subglacial water storage. 2-D modeling suggests 91-99 % of motion is sliding.
The Cryosphere Discuss., 9, 4067-4116, doi:10.5194/tcd-9-4067-2015, 2015
Subglacial hydrology indicates a major shift in dynamics of the West Antarctic Ross Ice Streams within the next two centuries
Summary: The Ross Ice Streams in West Antarctica showed a high variability in the past. We model basal water pathways and catchment areas for present and future ice sheet geometries (gained by applying satellite-derived elevation change rates) in this sector. Thus, we can explain the current ice stream configuration and estimate implications for the next two centuries, where we find that a major basal hydraulic tributary of the Kamb and Whillans IS could be redirected underneath the Bindschadler IS.
The Cryosphere Discuss., 9, 3995-4018, doi:10.5194/tcd-9-3995-2015, 2015
Climatic controls and climate proxy potential of Lewis Glacier, Mt Kenya
The Cryosphere Discuss., 9, 3887-3924, doi:10.5194/tcd-9-3887-2015, 2015
Glaciers change over the last century, Caucasus Mountains, Georgia, observed by the old topographical maps, Landsat and ASTER satellite imagery
Summary: The article presents the percentage and quantitative changes in the number and area of the glaciers of Georgia (Caucasus) in the years of 1911-1960-1975-2014, according to the individual river basins. The air temperature course of the Georgia’s high mountain weather stations has been studied. The river basins have been revealed, where there are the highest indices of the reduction in area and number of the glaciers and the reasons have been explained.
The Cryosphere Discuss., 9, 3777-3806, doi:10.5194/tcd-9-3777-2015, 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