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The measurement of glacier velocity fields using repeat satellite imagery has become a standard method of cryospheric research. However, the reliable discovery of important glacier velocity variations on a large scale is still problematic because time series span different time intervals and are partly populated with erroneous velocity estimates. In this study we build upon existing glacier velocity products from the GoLIVE dataset (https://nsidc.org/data/golive, last access: 26 February 2019) and compile a multi-temporal stack of velocity data over the Saint Elias Mountains and vicinity. Each layer has a time separation of 32 days, making it possible to observe details such as within-season velocity change over an area of roughly 150 000 km2. Our methodology is robust as it is based upon a fuzzy voting scheme applied in a discrete parameter space and thus is able to filter multiple outliers. The multi-temporal data stack is then smoothed to facilitate interpretation. This results in a spatiotemporal dataset in which one can identify short-term glacier dynamics on a regional scale. The goal is not to improve accuracy or precision but to enhance extraction of the timing and location of ice flow events such as glacier surges. Our implementation is fully automatic and the approach is independent of geographical area or satellite system used. We demonstrate this automatic method on a large glacier area in Alaska and Canada. Within the Saint Elias and Kluane mountain ranges, several surges and their propagation characteristics are identified and tracked through time, as well as more complicated dynamics in the Wrangell Mountains.

Retreating glaciers and thawing permafrost are causing local- to regional-scale hazards that threaten lives and livelihoods, infrastructure, sustainable resource development, and national security. Permafrost hazards are gradually impacting people across the Arctic, while glacier/permafrost hazard cascades are abrupt, more localized, and most life threatening. Broad-scale hazard identification and assessment across the Arctic are needed to better inform stakeholder decision making.

Andreas Kääb Nicht alle Gebirgsgletscher der Erde fließen gemächlich, mit typischen Geschwindigkeiten von wenigen Metern bis hunderten von Metern pro Jahr. Einzelne Gletscher können instabil werden und sich vorübergehend viel schneller bewegen. Sogenannte »galoppierende« Gletscher, meist mit dem englischen Fachbegriff »surges« bezeichnet, fließen über Zeiträume von Monaten bis zu wenigen Jahren mit bis zu mehreren Kilometern pro Jahr und stoßen dabei oft auch über mehrere Kilometer vor. Bei einer weiteren Art von Gletscherinstabilität, Eislawinen, bricht von steilen Gletscherpartien Eis ab und erzeugt Lawinen, ähnlich Schneelawinen. Eine dritte seltene Art von Gletscherinstabilitäten, die erst vor kurzem erkannt wurde, kombiniert die großen Volumina von »surges« mit den hohen Geschwindigkeiten von Eislawinen. Bei diesen Gletscherlawinen rutschen große Teile flacher Gebirgsgletscher, mit einem Volumen von bis zu 100 Millionen Kubikmeter und mehr, plötzlich ab und rasen mit Geschwindigkeiten bis zu 300 km/h zu Tale. Die Klimaerwärmung verändert wo, wie häufig und wie große Gletscherinstabilitäten in den Hochgebirgen und den Polarregionen der Erde geschehen können. Allerdings sind die Wechselwirkungen diese Ereignisse mit dem Klima (z.B. Anstieg der Lufttemperaturen, Veränderung des Niederschlags) sehr komplex. Je nach lokalen Gegebenheiten können die Gefahren aus diesen Prozessen zu- oder abnehmen. When glaciers slide down: Not all mountain glaciers on Earth flow slowly, with typical speeds of a few meters to hundreds of meters per year. Individual glaciers can become unstable and temporarily move much faster. So-called surging glaciers flow over periods of months to a few years at up to several kilometres per year, and often advance over several kilometres. In another type of glacier instability, ice avalanches, ice breaks off from steep glacier areas and creates avalanches, similar to snow avalanches. A third, though rare type of glacier instability, which was only recently recognized, combines the large volumes of glacier surges with the high speeds of ice avalanches. In these glacier detachments, large parts of flat mountain glaciers, up to 100 million cubic meters and more, suddenly slide off and race down a valley at speeds of up to 300 km / h. Global warming is changing where, how often and how large glacier instabilities can occur in the high mountains and Polar Regions of the world. Changes in ice avalanches, glacier surges, and glacier detachments, however, are associated in a complex way with an increase in air temperatures. Depending on local conditions, the hazards from these processes can increase or decrease.

Raw data of "Subglacial permafrost dynamics and erosion inside subglacial channels driven by surface events in Svalbard" published in The Cryosphere. This data comprises temperature data from subglacial drainage systems of two glacier on Svalbard. Given are dates with time and temperatures in °C. The following temperatures are measured: Air temperatures inside drainage systems (called air), ice temperatures and sediment temperatures. Detailed descriptions of the measurements can be found in: https://doi.org/10.5194/tc-2020-124

This is chapter 4 of the State of Environmental Science in Svalbard (SESS) report 2019 (https://sios-svalbard.org/SESS_Issue2). Glacier mass balance is the budget between snow accumulation and melting of snow and ice. Where glaciers terminate in the ocean, calving of icebergs constitutes an additional mechanism of mass loss, though it is more difficult to assess than snow accumulation and surface melting. The SvalGlac report reviews new technologies and new data that have become available in the past 20 years to update previous assessments. We find that glaciers all over Svalbard are losing mass, with rates depending on geographical location and glacier size. Smaller glaciers in southern Spitsbergen experience highest rates of mass loss while large ice caps in Northeast Svalbard are closer to a balance situation. However, variations from year to year are large and long-term observations are needed to recognise trends. These spatial patterns and temporal evolution are also supported by modelling studies that calculate surface mass balance based on meteorological data, and by studies applying satellite remote sensing. The only available estimate of calving needs updating, especially with regard to year-to-year and seasonal variations. Several large surges have occurred in the past few years, strongly influencing the amount of ice discharged into the ocean. A glacier surge is a switch from a slow to fast flowing mode, sometimes happening periodically. The mechanisms responsible for surges are not well understood but several Svalbard-based studies shed new light on these processes. The most important gaps are: • our incomplete understanding of surging, both the process itself and its implications for Svalbard glacier mass balance • incomplete basic data coverage for quantification of calving and • limited information about glacier mass balance and meltwater runoff in a future climate.

Permafrost is present within almost all of the Antarctic's ice-free areas, but little is known about spatial variations in permafrost temperatures except for a few areas with established ground temperature measurements. We modelled a temperature at the top of the permafrost (TTOP) for all the ice-free areas of the Antarctic mainland and Antarctic islands at 1 km2 resolution during 2000–2017. The model was driven by remotely sensed land surface temperatures and downscaled ERA-Interim climate reanalysis data, and subgrid permafrost variability was simulated by variable snow cover. The results were validated against in situ-measured ground temperatures from 40 permafrost boreholes, and the resulting root-mean-square error was 1.9 ∘C. The lowest near-surface permafrost temperature of −36 ∘C was modelled at Mount Markham in the Queen Elizabeth Range in the Transantarctic Mountains. This is the lowest permafrost temperature on Earth, according to global-scale modelling results. The temperatures were most commonly modelled between −23 and −18 ∘C for mountainous areas rising above the Antarctic Ice Sheet and between −14 and −8 ∘C for coastal areas. The model performance was good where snow conditions were modelled realistically, but errors of up to 4 ∘C occurred at sites with strong wind-driven redistribution of snow.

Societal dependence on, and commercial and scientific exploitation of Earth-Oriented remote sensing from satellites is growing at an exponential rate. The comprehensive EU Copernicus programme provides a major contribution to the global effort, but even so, to achieve the necessary global and temporal coverage requires synergistic cooperation and associated interoperability of the Worlds sensors. For a user to exploit Earth Observation (EO) data there must exist confidence in data characteristics, quality and reliable delivery. Although long-term data records for climate may be the most demanding in nature, generation of analysis-ready operational data sets for applications, as diverse as food security to pollution monitoring, all require the user to have some quantitative level of confidence in the data and derived information. A long-term Calibration/Validation (Cal/Val) vision necessitates clear ownership and long-term funding. Delineating the roles of the European Commission (EC), space agencies and member states in long-term Cal/Val would provide clarity. It is clear that the space agencies have the responsibility to meet the mission requirement of their spaceborne instruments but long-term validation is often entrusted to interested parties bringing their own resources to the task. Furthermore, there is a critical need for Fiducial Reference Measurements (FRMs), acquired in operational mode, and comprehensive in coverage both spatially and temporally, to assure that the satellite product accuracies are met. This paper discusses the current status, gaps and challenges regarding long-term Cal/Val of EO satellites and recommends the creation of a European coordinating entity for satellite product calibration and validation. The proposed entity would be an integrative organization coordinating the European Cal/Val activities in partnership with the member states and the space agencies and working together with existing data providers to secure access to satellite and in-situ data of traceable FRM standards.