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Abstract. Permafrost is a key element of the terrestrial cryosphere which makes mapping and monitoring of its state variables an imperative task. We present a modeling scheme based on remotely sensed land surface temperatures and reanalysis products from which mean annual ground temperatures (MAGT) can be derived at a spatial resolution of 1 km at continental scales. The approach explicitly accounts for the uncertainty due to unknown input parameters and their spatial variability at subgrid scale by delivering a range of MAGTs for each grid cell. This is achieved by a simple equilibrium model with only few input parameters which for each grid cell allows scanning the range of possible results by running many realizations with different parameters. The approach is applied to the unglacierized land areas in the North Atlantic region, an area of more than 5 million km2 ranging from the Ural Mountains in the east to the Canadian Archipelago in the west. A comparison to in situ temperature measurements in 143 boreholes suggests a model accuracy better than 2.5 °C, with 139 considered boreholes within this margin. The statistical approach with a large number of realizations facilitates estimating the probability of permafrost occurrence within a grid cell so that each grid cell can be classified as continuous, discontinuous and sporadic permafrost. At its southern margin in Scandinavia and Russia, the transition zone between permafrost and permafrost-free areas extends over several hundred km width with gradually decreasing permafrost probabilities. The study exemplifies the unexploited potential of remotely sensed data sets in permafrost mapping if they are employed in multi-sensor multi-source data fusion approaches.

Abstract. Estimating the long-term mass balance of the high-Arctic Svalbard archipelago is difficult due to the incomplete geodetic and direct glaciological measurements, both in space and time. To close these gaps, we use a coupled surface energy balance and snow pack model to analyse the mass changes of all Svalbard glaciers for the period 1957–2014. The model is forced by ERA-40 and ERA-Interim reanalysis data, downscaled to 1 km resolution. The model is validated using snow/firn temperature and density measurements, mass balance from stakes and ice cores, meteorological measurements, snow depths from radar profiles and remotely sensed surface albedo and skin temperatures. Overall model performance is good, but it varies regionally. Over the entire period the model yields a climatic mass balance of 8.2 cm w. e.  yr−1, which corresponds to a mass input of 175 Gt. Climatic mass balance has a linear trend of −1.4 ± 0.4 cm w. e.  yr−2 with a shift from a positive to a negative regime around 1980. Modelled mass balance exhibits large interannual variability, which is controlled by summer temperatures and further amplified by the albedo feedback. For the recent period 2004–2013 climatic mass balance was −21 cm w. e.  yr−1, and accounting for frontal ablation estimated by Błaszczyk et al.(2009) yields a total Svalbard mass balance of −39 cm w. e.  yr−1 for this 10-year period. In terms of eustatic sea level, this corresponds to a rise of 0.037 mm yr−1. Refreezing of water in snow and firn is substantial at 22 cm w. e.  yr−1 or 26 % of total annual accumulation. However, as warming leads to reduced firn area over the period, refreezing decreases both absolutely and relative to the total accumulation. Negative mass balance and elevated equilibrium line altitudes (ELAs) resulted in massive reduction of the thick (>  2 m) firn extent and an increase in the superimposed ice, thin (<  2 m) firn and bare ice extents. Atmospheric warming also leads to a marked change in the thermal regime, with cooling of the glacier mid-elevation and warming in the ablation zone and upper firn areas. On the long-term, by removing the thermal barrier, this warming has implications for the vertical transfer of surface meltwater through the glacier and down to the base, influencing basal hydrology, sliding and thereby overall glacier motion.

Abstract. Permafrost is a key element of the terrestrial cryosphere which makes mapping and monitoring of its state variables an imperative task. We present a modeling scheme based on remotely sensed land surface temperatures and reanalysis products from which mean annual ground temperatures (MAGT) can be derived at a spatial resolution of 1 km on continental scale. The approach explicitly accounts for the uncertainty due to unknown input parameters and their spatial variability at subgrid scale by delivering a range of MAGTs for each grid cell. This is achieved by a simple equilibrium model with only few input parameters which for each grid cell allows scanning the range of possible results by running many realizations with different parameters. The approach is applied to the unglacierized land areas in the North Atlantic region, an area of more than 5 million km2 ranging from the Ural mountains in the East to the Canadian Archipelago in the West. A comparison to in-situ temperature measurements in 143 boreholes suggests a model accuracy better than 2.5 °C, with 139 considered boreholes within this margin. The statistical approach with a large number of realizations facilitates estimating the probability of permafrost occurrence within a grid cell so that each grid cell can be classified as continuous, discontinuous and sporadic permafrost. At its southern margin in Scandinavia and Russia, the transition zone between permafrost and permafrost-free areas extends over several hundred km width with gradually decreasing permafrost probabilities. The study exemplifies the unexploited potential of remotely sensed data sets in permafrost mapping if they are employed in multi-sensor multi-source data fusion approaches.

Only few reliable records are available covering more than 5 years of meteorological conditions on Arctic glaciers. Here, we report on the operation of an automatic weather station at the Austfonna ice cap, Svalbard, over an 8-year period from 2004 to 2012. Time series of measured and derived quantities are analysed to characterize meteorological conditions close to the equilibrium line altitude at ∼400 m.a.s.l. The mean annual temperature is −8.3 • C but exhibits large variability such that excursions above 0 • C occur even during winter. In general, relative air humidity is high and evaluating the wind pattern, we find that moisture is primarily advected from south-easterly directions. Net radiation is dominated by shortwave radiation and, hence, surface albedo plays an important role in the radiation budget. Frequent summer snowfalls, as observed in 2008, have the ability to maintain a high albedo over much of the ablation season, thereby having large impact on the energy balance as well as on glacier mass balance. Cloudiness is assessed using records of incoming longwave radiation. Analyzing the radiation data, we find evidence for the radiation paradox, i.e. an increase of average net radiation (2004-2012) from −15.7 W m −2 for clear-sky conditions to 7.3 W m −2 during overcast skies.