Abstract. Glacier fluctuations contribute to variations in sea level and historical glacier length fluctuations are natural indicators of past climate change. To study these subjects, long-term information of glacier change is needed. In this paper we present a data set of global long-term glacier length fluctuations. The data set is a compilation of available information on changes in glacier length worldwide, including both measured and reconstructed glacier length fluctuations. All 471 length series start before 1950 and cover at least four decades. The longest record starts in 1535, but the majority of time series start after 1850. The number of available records decreases again after 1962. The data set has global coverage including records from all continents. However, the Canadian Arctic is not represented in the data set. The available glacier length series show relatively small fluctuations until the mid-19th century, followed by a global retreat. The retreat was strongest in the first half of the 20th century, although large variability in the length change of the different glaciers is observed. During the 20th century, calving glaciers retreated more than land-terminating glaciers, but their relative length change was approximately equal. Besides calving, the glacier slope is the most important glacier property determining length change: steep glaciers have retreated less than glaciers with a gentle slope.

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Changes in area of 30 small glaciers (mostly <1 km2) in the northern Polar Urals (67.568.25° N) between 1953 and 2000 were assessed using historic aerial photography from 1953 and 1960, ASTER and panchromatic Landsat ETM+ imagery from 2000, and data from 1981 and 2008 terrestrial surveys. Changes in volume and geodetic mass balance of IGAN and Obruchev glaciers were calculated using data from terrestrial surveys in 1963 and 2008. In total, glacier area declined by 22.3 ± 3.9% in the 1953/60-2000 period. The areas of individual glaciers decreased by 4-46%. Surfaces of Obruchev and IGAN glaciers lowered by 22.5 ± 1.7 m and 14.9 ± 2.1 m. Over 45 years, geodetic mass balances of Obruchev and IGAN glaciers were -20.66 ± 2.91 and -13.54 ± 2.57 mw.e. respectively. Glacier shrinkage in the Polar Urals is related to a summer warming of 1°C between 1953-81 and 1981-2008 and its rates are consistent with other regions of northern Asia but are higher than in Scandinavia. While glacier shrinkage intensified in the 1981-2000 period relative to 1953-81, increasing winter precipitation and shading effects slowed glacier wastage in 2000-08.

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The glaciers and ice caps in the Arctic are experiencing noticeable changes which are manifested, in particular, in the intensification of their dynamic instability. In this paper we present data on a largescale surge in the Western basin of the Vavilov ice dome on the archipelago Severnaya Zemlya, derived from satellite images and supplemented by airborne RES-2014 and available publications. Analysis of 28 space images of 1963–2017 demonstrated that the surge developed over the whole period. In the fi st decade (1963–1973), the advance was very slow – from 2–5 to 12 m/year. Since the 1980-ies, the ice movement began to accelerate from tens to a hundred of meters per a year in the 2000-ies. The sudden change happened in the year 2012 when the surge front began to move already at speeds of about 0.5 km/year. In 2015, the volume of advanced part reached almost 4 km3. Maximal speed 9.2 km/year was recorded in 2016. From 1963 to 2017, the edge of the glacier advanced by 11.7 km, and its area increased by 134.1 km2 (by 47% relative to the basin area of 1963), that caused spreading of crevasse zone up the glacier. Surface speeds reached a maximum of 25.4 m/day in 2016 and decreased to 7.6 m/day in 2017. The authors suggest that the initial activation of the southern and western edges of the ice dome could be a reaction to the climate signal, possibly occurred several centuries ago. The ice crevassing and cryo-hydrological warming of ice, enhanced by positive feedback, resulted in instability of the glacier and the displacement of the edge of the ice belt containing moraine and frozen to the bed, which transformed into a catastrophic movement. The surge was facilitated by change of bedrock conditions as the ice lobe progressed offshore from permafrost coastal zone to the area of loose marine bottom sediments with low shear strength. The surge seems to be also stimulated by anomalously warm summer of 2012.