Circum-Arctic changes in the flow of glaciers and ice caps from satellite SAR data between the 1990s and 2017

We computed circum-Arctic surface velocitymaps of glaciers and ice caps over the Canadian Arctic, Svalbard and the Russian Arctic for at least two times between the 1990s and 2017 using satellite SAR data. Our analyses are mainly performed with offset-tracking of ALOS-1 PALSAR-1 (2007–2011) and Sentinel-1 (2015–2017) data. In certain cases JERS-1 SAR (1994–1998), TerraSAR-X (2008–2012), Radarsat-2 (2009–2016) and ALOS-2 PALSAR-2 (2015–2016) data were used to fill-in spatial or temporal gaps. Validation of the latest Sentinel-1 results was accomplished by means of SAR data at higher spatial resolution (Radarsat-2Wide Ultra Fine) and ground-basedmeasurements. In general, we observe a deceleration of flow velocities for the major tidewater glaciers in the Canadian Arctic and an increase in frontal velocity along with a retreat of frontal positions over Svalbard and the Russian Arctic. However, all regions have strong accelerations for selected glaciers. The latter developments can be well traced based on the very high temporal sampling of Sentinel-1 acquisitions since 2015, revealing new insights in glacier dynamics. For example, surges on Spitsbergen (e.g., Negribreen, Nathorsbreen, Penckbreen and Strongbreen) have a different characteristic and timing than those over Eastern Austfonna and Edgeoya (e.g., Basin 3, Basin 2 and Stonebreen). Events similar to those ongoing on Eastern Austofonna were also observed over the Vavilov Ice Cap on Severnaya Zemlya and possibly Simony Glacier on Franz-Josef Land. Collectively, there seems to be a recently increasing number of glaciers with frontal destabilization over Eastern Svalbard and the Russian Arctic compared to the 1990s

Новый Каталог ледников России по спутниковым данным (2016–2019 гг.)

The new Inventory of the Russian glaciers has been created at the Institute of Geography of the Russian Academy of Sciences mainly on the basis of the Sentinel 2 satellite images for 2016–2019 with the aim of assessing the current state of glacier systems and as a basis for monitoring and re-inventorying. Delineation of glacier outlines was manually made to reduce uncertainties, especially for small glaciers. The database structure is compatible with the global and national glacier archives and includes the main glacial parameters. Additionally a classification of possible catastrophic phenomena of glacial genesis was developed: dynamically unstable glaciers, glacier lakes, icebergs, etc. The data base is available online (www.glacrus.ru). At present, there are 22 glacial systems in Russia with a total area of 54,518 km2. The largest glacial systems by area are located in the Arctic archipelagos: Novaya Zemlya, Severnaya Zemlya, and Franz Josef Land. The glacial systems of the Caucasus, Kamchatka, and Altai are the largest by area in the continental part of Russia. The main group consists of 13 small glacial systems, the area of which does not exceed 100 km2. They are located in different glaciological zones: from the De Long Islands in the Arctic to the Eastern Sayan in southern Siberia. Since the compilation of the USSR glacier Inventory (1965–1982), the area of glaciers has decreased by 5,594 km2, or 9.3%. The area of polar glaciers has decreased in smaller degree than that of glaciers in mountainous regions. The results of our research confirm the trend of reducing the area of glaciers throughout the Russian territory. The magnitude and rate of changes depend on local climatic and orographic features. The exception is the glaciers of the volcanic regions of Kamchatka, the area of which has increased or remained unchanged.Создан Каталог ледников России на основе спутниковых снимков Sentinel‑2 (2016–2019 гг.) (www.glacrus.ru). Он содержит информацию о 22-х ледниковых системах общей площадью 54 518 км2. По сравнению с Каталогом ледников СССР (1965–1982 гг.) площадь ледников на территории России уменьшилась на 5594 км2, или на 9,3%. Величина и скорость изменений в разных районах сильно отличаются и зависят от местных климатических и орографических особенностей

Поверхностные скорости и айсберговый сток ледникового купола Академии Наук на Северной Земле

We have determined the ice-surface velocities of the Academy of Sciences Ice Cap, Severnaya Zemlya, Russian Arctic, during the period November 2016 – November 2017, using intensity offset-tracking of Sentinel-1 synthetic-aperture radar images. We used the average of 54 pairs of weekly velocities (with both images in each pair separated by a12-day period) to estimate the mean annual ice discharge from the ice cap. We got an average ice discharge for 2016–2017 of 1,93±0,12 Gt a−1, which is equivalent to −0,35±0,02 m w.e. a−1 over the whole area of the ice cap. The difference from an estimate of ~1,4 Gt a−1 for 2003–2009 can be attributed to the initiation of ice-stream flow in Basin BC sometime between 2002 and 2016. Since the front position changes between both periods have been negligible, ice discharge is equivalent to calving flux. We compare our results for calving flux with those of previous studies and analyse the possible drivers of the changes observed along the last three decades. Since these changes do not appear to have responded to environmental changes, we conclude that the observed changes are likely driven by the intrinsic characteristics of the ice cap governing tidewater glacier dynamics.По 54 парам космических снимков Sentinel‐1, сделанных с ноября 2016 г. по ноябрь 2017 г., определены скорости движения ледникового купола Академии Наук на Северной Земле. На этой основе оценён среднегодовой расход льда в море этого купола (1,93±0,12 Гт/год), установлены основные пути стока льда, проведено сравнение с прежними оценками

Развитие подвижки в западной части ледникового купола Вавилова на Северной Земле в 1963–2017 гг.

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.Исследованы скорости продвижения фронта и роста площади западного сектора ледникового купола Вавилова на Северной Земле с 1963 по 2017 г. Показано, как медленное продвижение фронта перешло в фазу катастрофической подвижки, которая достигла кульминации в 2016 г., когда скорости движения ледника достигали 9,2 км/год. В результате подвижки в акваторию Карского моря на расстояние 11,7 км выдвинулась ледниковая лопасть площадью 134,1 км2 и объёмом не менее 4 км3, начавшая продуцировать айсберги

Dynamic vulnerability revealed in the collapse of an Arctic tidewater glacier

Abstract Glacier flow instabilities can rapidly increase sea level through enhanced ice discharge. Surge-type glacier accelerations often occur with a decadal to centennial cyclicity suggesting internal mechanisms responsible. Recently, many surging tidewater glaciers around the Arctic Barents Sea region question whether external forces such as climate can trigger dynamic instabilities. Here, we identify a mechanism in which climate change can instigate surges of Arctic tidewater glaciers. Using satellite and seismic remote sensing observations combined with three-dimensional thermo-mechanical modeling of the January 2009 collapse of the Nathorst Glacier System (NGS) in Svalbard, we show that an underlying condition for instability was basal freezing and associated friction increase under the glacier tongue. In contrast, continued basal sliding further upstream increased driving stresses until eventual and sudden till failure under the tongue. The instability propagated rapidly up-glacier, mobilizing the entire 450 km2 glacier basin over a few days as the till entered an unstable friction regime. Enhanced mass loss during and after the collapse (5–7 fold compared to pre-collapse mass losses) combined with regionally rising equilibrium line altitudes strongly limit mass replenishment of the glacier, suggesting irreversible consequences. Climate plays a paradoxical role as cold glacier thinning and retreat promote basal freezing which increases friction at the tongue by stabilizing an efficient basal drainage system. However, with some of the most intense atmospheric warming on Earth occurring in the Arctic, increased melt water can reduce till strength under tidewater glacier tongues to orchestrate a temporal clustering of surges at decadal timescales, such as those observed in Svalbard at the end of the Little Ice Age. Consequently, basal terminus freezing promotes a dynamic vulnerability to climate change that may be present in many Arctic tidewater glaciers

Freshwater input to the Arctic fjord Hornsund (Svalbard)

Glaciers draining to the Hornsund basin (southern Spitsbergen, Svalbard) have experienced a significant retreat and mass volume loss over the last decades, increasing the input of freshwater into the fjord. An increase in freshwater input can influence fjord hydrology, hydrodynamics, sediment flux and biota, especially in a changing climate. Here, we describe the sources of freshwater supply to the fjord based on glaciological and meteorological data from the period 2006 to 2015. The average freshwater input from land to the Hornsund bay is calculated as 2517 ± 82 Mt a−1, with main contributions from glacier meltwater runoff (986 Mt a−1; 39%) and frontal ablation of tidewater glaciers (634 Mt a−1; 25%). Tidewater glaciers in Hornsund lose ca. 40% of their mass by frontal ablation. The terminus retreat component accounts for ca. 30% of the mass loss by frontal ablation, but it can vary between 17% and 44% depending on oceanological, meteorological and geomorphological factors. The contribution of the total precipitation over land excluding winter snowfall (520 Mt a−1), total precipitation over the fjord area (180 Mt a−1) and melting of the snow cover over unglaciated areas (197 Mt a−1) to the total freshwater input appear to be small: 21%, 7% and 8%, respectively

Estimation of Glacier Thickness From Surface Mass Balance and Ice Flow Velocities: A Case Study on Argentière Glacier, France

Glacier thickness distribution is a prerequisite to simulate the future of glaciers. Inaccurate thicknesses may lead to significant uncertainties in the timing of future changes to glaciers and their consequences for water resources or sea level rise. Unfortunately, glacier thickness distribution is rarely measured and consequently has to be estimated. In this study, we present an approach developed on the well documented Argentière Glacier (French Alps) that uses surface mass balance (SMB) together with surface flow velocity data to quantify glacier thickness distribution over the entire surface of the glacier. We compare the results of our approach to those obtained applying Farinotti et al. (2009) approach. Our results show that glacier thickness distribution are significantly biased when the glacier SMB profile used to quantify the ice fluxes is not constrained with in situ measurements. We also show that even with SMB measurements available on the studied glacier, ice flux estimates can be inaccurate. This inability to correctly estimate ice fluxes from the apparent SMB may be due to the steady state assumption that is not respected from the available glacier surface topography data. Therefore, ice thickness measurements on few cross sections (four are used in this study) are required to constrain the ice flux estimates and lead to an overall agreement between the ice thickness estimations and measurements. Using our approach, the ice thicknesses only differ by 10% from observations in average, but can differ by up to 150 m (or 30%) locally. We also show that approaches that use the glacier surface slope can lead to large uncertainties given that the quantification of the slope is highly uncertain. The approach presented here does not pretend to be applied globally but rather as a tool to quantify ice thickness distribution over the entire surface of glaciers for which a few in situ surface mass balance and thickness data are available together with surface flow velocities that can be obtained for example from remote sensing

Circum-Arctic Changes in the Flow of Glaciers and Ice Caps from Satellite SAR Data between the 1990s and 2017

We computed circum-Arctic surface velocity maps of glaciers and ice caps over the Canadian Arctic, Svalbard and the Russian Arctic for at least two times between the 1990s and 2017 using satellite SAR data. Our analyses are mainly performed with offset-tracking of ALOS-1 PALSAR-1 (2007–2011) and Sentinel-1 (2015–2017) data. In certain cases JERS-1 SAR (1994–1998), TerraSAR-X (2008–2012), Radarsat-2 (2009–2016) and ALOS-2 PALSAR-2 (2015–2016) data were used to fill-in spatial or temporal gaps. Validation of the latest Sentinel-1 results was accomplished by means of SAR data at higher spatial resolution (Radarsat-2 Wide Ultra Fine) and ground-based measurements. In general, we observe a deceleration of flow velocities for the major tidewater glaciers in the Canadian Arctic and an increase in frontal velocity along with a retreat of frontal positions over Svalbard and the Russian Arctic. However, all regions have strong accelerations for selected glaciers. The latter developments can be well traced based on the very high temporal sampling of Sentinel-1 acquisitions since 2015, revealing new insights in glacier dynamics. For example, surges on Spitsbergen (e.g., Negribreen, Nathorsbreen, Penckbreen and Strongbreen) have a different characteristic and timing than those over Eastern Austfonna and Edgeoya (e.g., Basin 3, Basin 2 and Stonebreen). Events similar to those ongoing on Eastern Austofonna were also observed over the Vavilov Ice Cap on Severnaya Zemlya and possibly Simony Glacier on Franz-Josef Land. Collectively, there seems to be a recently increasing number of glaciers with frontal destabilization over Eastern Svalbard and the Russian Arctic compared to the 1990s

Recent glacier change (1965 - 2021) and identification of surge-type glaciers on Severnaya Zemlya, Russian High Arctic

Glaciers in the Russian High Arctic are rapidly losing mass due to strong atmospheric and oceanic warming of the Barents-Kara Sea region. However, most studies have concentrated on Novaya Zemlya, despite a 29% acceleration in mass loss on Severnaya Zemlya (SZ) in the past decade (2003-2009 to 2010-2017). Research on SZ has formerly been hindered by its inaccessibility and limited data availability, with long-term trends in glacier change largely unknown. Moreover, records of glacier change on SZ may be complicated by evidence of surging, rather than solely due to climatic perturbations. In this thesis, an assessment of recent glacier change (1965 to 2021) on SZ is presented, along with a new inventory of surge-type glaciers from a high-resolution digital elevation model (Arctic DEM), declassified spy-satellite photography (KH-7/9 Hexagon), and optical satellite imagery (Sentinel 2, ASTER & Landsat 8 & TM). A total of 190 glaciers were mapped at five dates and surveyed for glaciological and geomorphological criteria indicative of former or active surging (e.g., thrust-block moraines and looped medial moraines). The results show that the glacierised area reduced from 17,053 km² in 1965 to 16,275 in 2021 (-778 km²) and retreat rates accelerated post-1997. There is no evidence of summer air temperature warming on northern SZ, with most glacier retreat occurring in the south of SZ where land-terminating glaciers have retreated (some up to 30%), attributed to emerging summer air temperature warming trends. Further north, glacier retreat is attributed to rising ocean temperatures and strong annual atmospheric warming which has likely lengthened the melt season. Additionally, four glaciers are classified as surge-type, seven as likely and nine as possible, comprising 11% of SZ’s glaciers. These glaciers occupy larger basins and are more likely to be marine or lake terminating