Permafrost is actively degrading across high latitudes due to climate warming. We combined thousands of end-of-summer active layer measurements, permafrost temperatures, geophysical surveys, deep borehole drilling, and repeat airborne lidar to quantify permafrost warming and thawing at sites across central Alaska. We calculate the mass of permafrost soil carbon potentially exposed to thaw over the past 7 years (0.44 Pg) is similar to the yearly carbon dioxide emissions of Australia.

Lake Fryxell, Antarctica, has undergone hundreds of meters of change in recent geologic history. However, there is disagreement on when lake levels were higher and by how much. This study uses resistivity data to map the subsurface conditions (frozen versus unfrozen ground) to map ancient shorelines. Our models indicate that Lake Fryxell was up to 60 m higher just 1500 to 4000 years ago. This amount of lake level change shows how sensitive these systems are to small changes in temperature.

Snow is frequently eroded from the surface by the wind in Adelie Land (Antarctica) and suspended in the lower atmosphere. By performing model simulations, we show firstly that suspended snow layers interact with incoming radiation similarly to a near-surface cloud. Secondly, suspended snow modifies the atmosphere's thermodynamic structure and energy exchanges with the surface. Our results suggest snow transport by the wind should be taken into account in future model studies over the region.

We use empirical run-time bias correction (also called flux correction) to correct the systematic errors of the ARPEGE atmospheric climate model. When applying the method to future climate projections, we found a lesser poleward shift and an intensification of the maximum of westerly winds present in the southern high latitudes. This yields a significant additional warming of +0.6 to +0.9 K of the Antarctic Ice Sheet with respect to non-corrected control projections using the RCP8.5 scenario.

We simulate the current state and future evolution of the Mocho-Choshuenco ice cap in southern Chile (40°S, 72°W) with the ice-sheet model SICOPOLIS. Under different global warming scenarios, we project ice mass losses between 56 % and 97 % by the end of the 21st century. We quantify the uncertainties based on an ensemble of climate models and on the temperature dependence of the equilibrium line altitude. Our results suggest a considerable deglaciation in southern Chile in the next 80 years.

We simulate the ice flow in the onset region of the Northeast Greenland Ice Stream to determine the source area and past accumulation rates of ice found in the EastGRIP ice core. This information is required to correct for bias in ice-core records introduced by the upstream flow effects. Our results reveal that the increasing accumulation rate with increasing upstream distance is predominantly responsible for the constant annual layer thicknesses observed in the upper 900 m of the ice core.

Pushed by winds and ocean currents, polar sea ice is on the move. We use passive microwave satellites to observe this motion. The images from their orbits are often put together into daily images before motion is measured. In our study, we measure motion from the individual orbits directly and not from the daily images. We obtain many more motion vectors, and they are more accurate. This can be used for current and future satellites, e.g. the Copernicus Imaging Microwave Radiometer (CIMR).

The study demonstrates the potential of photogrammetry for analyzing glacier retreat with high spatial resolution. Twenty-three glaciers within the Ötztal Alps are analyzed. We compare photogrammetric and glaciologic mass balances of the Vernagtferner by using the ELA for our density assumption and an UAV survey for a temporal correction of the geodetic mass balances. The results reveal regions of anomalous mass balance and allow estimates of the imbalance between mass balances and ice dynamics.

Ice core analyses are often done in home laboratories after costly transport of samples from the field. This limits the amount of sample that can be analysed. Here, we present the first truly field-portable continuous flow analysis (CFA) system for the analysis of impurities in snow, firn and ice cores while still in the field: the lightweight in situ analysis (LISA) box. LISA is demonstrated in Greenland to reconstruct accumulation, conductivity and peroxide in snow cores.

We present a unique insight into the shape and development of a subglacial lake over a 7-year period, using repeated radar survey. The lake collects geothermal meltwater, which is released in semi-regular floods, often referred to as jökulhlaups. The applicability of our survey approach to monitor the water stored in the lake for a better assessment of the potential hazard of jökulhlaups is demonstrated by comparison with independent measurements of released water volume during two jökulhlaups.

We compare the calculated surface mass budget (SMB) of Antarctica in five different regional climate models. On average ~ 2000 Gt of snow accumulates annually, but different models vary by ~ 10 %, a difference equivalent to ± 0.5 mm of global sea level rise. All models reproduce observed weather, but there are large differences in regional patterns of snowfall, especially in areas with very few observations, giving greater uncertainty in Antarctic mass budget than previously identified.

This study presents new methods to assess how well observations of sea ice expansion are reproduced by results from models. The aim is to provide information about the quality of forecasts for changes in the sea ice extent to operators in or near ice-infested waters. A test using 2 years of model results demonstrates the practical applicability and usefulness of the methods that are presented.

Our results show three main sea ice drift patterns have different multiscale variation characteristics. The oscillation period of the third sea ice transport pattern is longer than the other two, and the ocean environment has a more significant influence on it due to the different regulatory effects of the atmosphere and ocean environment on sea ice drift patterns on various scales. Our research can provide a basis for the study of Arctic sea ice dynamics parameterization in numerical models.

We investigate how snow avalanche activity in central Spitsbergen, Svalbard, is broadly controlled by atmospheric circulation. Avalanche activity in this region is generally associated with atmospheric circulation conducive to increased precipitation, wind speeds, and air temperatures near Svalbard during winter storms. Our results help place avalanche activity on Spitsbergen in the wider context of Arctic environmental change and provide a foundation for improved avalanche forecasting here.

Projections of global sea-level changes in a warming world require ice-sheet models. We expand the calibration of these models by making use of the internal architecture of the Antarctic ice sheet, which is formed by its evolution over many millennia. We propose that using our novel approach to constrain ice sheet models, we will be able to both sharpen our understanding of past and future sea-level changes and identify weaknesses in the parameterisation of current continental-scale models.

We investigate the disintegration of the B30 iceberg using satellite remote sensing and find that the iceberg lost 378 km³ of ice in 6.5 years, corresponding to 80 % of its initial volume. About two thirds are due to fragmentation at the sides, and one third is due to melting at the iceberg’s base. The release of fresh water and nutrients impacts ocean circulation, sea ice formation, and biological production. We show that adding a snow layer is important when deriving iceberg thickness.

We assess the climatic controls of melt lake development, melt duration, melt extent, and the spatial distribution of lakes of 79°N Glacier. There is a large interannual variability in the areal extent of the lakes and the maximum elevation of lake development, which is largely controlled by the summertime air temperatures and the snowpack thickness. Late-summer lake development can be prompted by spikes in surface mass balance. There is some evidence of inland expansion of lakes over time.

We use satellite data records collected along the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) drift to categorize ice conditions that shaped and characterized the floe and surroundings during the expedition. A comparison with previous years is made whenever possible. The aim of this analysis is to provide a basis and reference for subsequent research in the six main research areas of atmosphere, ocean, sea ice, biogeochemistry, remote sensing and ecology.

The role of snow microstructure in snow optical properties is only partially understood despite the importance of snow optical properties for the Earth system. We present a dataset combining bidirectional reflectance measurements and 3D images of snow. We show that the snow reflectance is adequately simulated using the distribution of the ice chord lengths in the snow microstructure and that the impact of the morphological type of snow is especially important when ice is highly absorptive.

A service to enable real-time optimization of grooming and snow-making at ski resorts was developed and evaluated using both GNSS-measured snow depth and spaceborne snow maps derived from Copernicus Sentinel-2. The correlation to the ground observation data was high. Potential sources for the overestimation of the snow depth by the simulations are mainly the impact of snow redistribution by skiers, compensation of uneven terrain, or spontaneous local adaptions of the snow management.

In this field study, we acquired a 3D radar survey over an active drainage network that transported meltwater through a Swiss glacier. We successfully imaged both englacial and subglacial pathways and were able to confirm long-standing glacier hydrology theory regarding meltwater pathways. The direction of these meltwater pathways directly impacts the glacier's velocity, and therefore more insightful field observations are needed in order to improve our understanding of this complex system.

Methods have been developed for calibrating sea ice drift forecasts from an operational prediction system using machine learning algorithms. These algorithms use predictors from sea ice concentration observations during the initialization of the forecasts, sea ice and wind forecasts, and some geographical information. Depending on the calibration method, the mean absolute error is reduced between 3.3 % and 8.0 % for the direction and between 2.5 % and 7.1 % for the speed of sea ice drift.

Polygon-shaped landforms present in relatively flat Arctic tundra result in complex landscape-scale water drainage. The drainage pathways and the time to transition from inundated conditions to drained have important implications for heat and carbon transport. Using fundamental hydrologic principles, we investigate the drainage pathways and timing of individual polygons, providing insights into the effects of polygon geometry and preferential flow direction on drainage pathways and timing.

This research proposes and tests new methods for the estimation of the surface roughness of newly formed river ice covers. The hypothesis sought to determine if surface ice roughness was indicative of the subsurface. Ice roughness has consequences for winter flow characteristics of rivers and can greatly impact river ice jams. Remotely piloted aircraft and photogrammetry were used, and good correlation was found between the observed surface ice roughness and estimated subsurface ice roughness.

As the hydraulic permeability of sea ice is difficult to measure, observations are sparse. The present work presents numerical simulations of the permeability of young sea ice based on a large set of 3D X-ray tomographic images. It extends the relationship between permeability and porosity available so far down to brine porosities near the percolation threshold of a few per cent. Evaluation of pore scales and 3D connectivity provides novel insight into the percolation behaviour of sea ice.

Ryder Glacier is a marine-terminating glacier in north Greenland discharging ice into the Lincoln Sea. Here we use marine sediment cores to reconstruct its retreat and advance behavior through the Holocene. We show that while Sherard Osborn Fjord has a physiography conducive to glacier and ice tongue stability, Ryder still retreated more than 40 km inland from its current position by the Middle Holocene. This highlights the sensitivity of north Greenland's marine glaciers to climate change.

Ice shelf meltwater in the surface ocean affects sea ice formation, causing it to be thicker and, in particular conditions, to have a loose mass of platelet ice crystals called a sub‐ice platelet layer beneath. This causes the sea ice freeboard to stand higher above sea level. In this study, we demonstrate for the first time that the signature of ice shelf meltwater in the surface ocean manifesting as higher sea ice freeboard in McMurdo Sound is detectable from space using satellite technology.

If the molecules that make up ice are oriented in specific ways, the ice becomes softer and enhances flow. We use radar to measure the orientation of ice molecules in the top 1400 m of the Western Antarctic Ice Sheet Divide. Our results match those from an ice core extracted 10 years ago and conclude that the ice flow has not changed direction for the last 6700 years. Our methods are straightforward and accurate and can be applied in places across ice sheets unsuitable for ice coring.

In our study we dated a 46 m deep ice core retrieved from the Adamello glacier (Central Italian Alps). We obtained a timescale combining the results of radionuclides ²¹⁰Pb and ¹³⁷Cs with annual layer counting derived from pollen and refractory black carbon concentrations. Our results indicate that the surface of the glacier is older than the drilling date of 2016 by about 20 years, therefore revealing that the glacier is at high risk of collapsing under current climate warming conditions.

Glacial lake outburst floods (GLOFs) in the greater Himalayan region threaten local communities and infrastructure. We assess this hazard objectively using fully data-driven models. We find that lake and catchment area, as well as regional glacier-mass balance, credibly raised the susceptibility of a glacial lake in our study area to produce a sudden outburst. However, our models hardly support the widely held notion that rapid lake growth increases GLOF susceptibility.