Significant retreat of glaciers terminating in Hornsund Fjord (Southern Spits− bergen, Svalbard) has been observed during the 20 th century and in the first decade of the 21 st century. The objective of this paper is to present, as complete as possible, a record of front positions changes of 14 tidewater glaciers during this period and to distinguish the main factors influencing their fluctuations. Results are based on a GIS analysis of archival maps, field measurements, and aerial and satellite images. Accuracy was based on an as− sessment of seasonal fluctuations of a glacier's ice cliff position with respect to its mini− mum length in winter (November-December) and its maximum advance position in June or July. Morphometric features and the environmental setting of each glacier are also pre− sented. The total area of the glacier cover in Hornsund Fjord in the period of 1899-2010 diminished approximately 172 km 2 , with an average areal retreat rate of 1.6 km 2 a −1 . The recession rate increased from~1 km 2 a −1 in first decades of the 20 th century up to~3 km 2 a −1 in years 2001-2010. The latest period was more thoroughly studied using optical satellite images acquired almost every year. The importance of glacier morphology and hypso− metry, as well as fjord bathymetry and topography is analyzed. Large glacier systems with low slopes terminating in deeper waters are retreating faster than small steep glaciers ter− minating in shallower water. A relation between mean annual air temperature and aerial retreat rate of tidewater glaciers was found for long time scales. A sudden temperature in− crease, known as the early 20 th century warming in Svalbard, and an increase in tempera− tures during recent decades are well reflected in deglaciation rate. Influence of sea water temperatures on calving and retreat of glaciers was considered and is significant in short−time intervals of the last decade. Surge events are non−climatic factors which com− plicate the record. They are reflected in front advance or fast retreat due to a massive calv− ing depending on the relation between ice thickness and water depth. Despite the influ− ence of many factors, the response of tidewater glaciers to climate change is evident. The average linear retreat rate of all the tidewater glaciers in Hornsund amounted to~70 ma −1 in 2001-2010 and was higher than the average retreat of other Svalbard tidewater glaciers (~45 ma −1 ). Thus, glaciers of this basin can be considered as more sensitive to climate than glaciers of other regions of the archipelago.

Climate-driven ice-water interactions in the contact zone between marine-terminating glaciers and the ocean surface show a dynamic and complex nature. Tidewater glaciers lose volume through the poorly understood process of calving. A detailed description of the mechanisms controlling the course of calving is essential for the reliable estimation and prediction of mass loss from glaciers. Here we present the potential of hydroacoustic methods to investigate different modes of ice detachments. High-frequency underwater ambient noise recordings are combined with synchronized, high-resolution, time-lapse photography of the Hans Glacier cliff in Hornsund Fjord, Spitsbergen, to identify three types of calving events: typical subaerial, sliding subaerial, and submarine. A quantitative analysis of the data reveals a robust correlation between ice impact energy and acoustic emission at frequencies below 200 Hz for subaerial calving. We suggest that relatively inexpensive acoustic methods can be successfully used to provide quantitative descriptions of the various calving types.

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.

Glacierised coasts undergo faster geomorphic processes than unglaciated ones. We have studied changes of the coastal area in southern Svalbard with the glacier bridge between Torell Land and Sørkapp Land since the beginning of the 20th century. The existence of a continuous subglacial depression beneath the Hornbreen–Hambergbreen glacier system has been debated since the 1960s, with inconclusive results. In this study we assess both the subglacial topography and the bathymetry of Hornsund Fjord and Hambergbukta bay. This included ~40 km of radar surveys over the glacial system and sea depth sounding. The extent of the glaciers from maps and satellite images together with digital terrain models and surface elevation data based on GPS profiling were used to analyse geometry changes of the glacier surfaces. The results confirm the existence of a continuous subglacial depression below sea level (c. 40 m deep) between Hornsund and the Barents Sea. The Hornbreen‐Hambergbreen system has changed in shape over the past century, reflecting its dynamic origin and activity, also exemplified by the sequential surges identified since 1899. There was a pre‐surge build‐up event of Flatbreen causing a surge and subsequent lowering of the Hornbreen‐Hambergbreen frontal parts by the 1960s. After, the entire surface lowered, albeit with a delay in the Hornbreen terminal zone. Since the year 2000, Hornbreen terminus has retreated at an average rate of 106 m a−1; ~50% faster than that of Hambergbreen. If the retreat continues at the 2000–2015 average rate, the ice bridge between Hornsund and Hambergbukta will be broken sometime between 2055 and 2065 and the Hornsund strait will separate Sørkapp Land from the Spitsbergen island. The processes and events described in this study, particularly the effects of the glacier surge, may provide a model for changes likely to occur in other coastal glaciated regions experiencing rapid change. Copyright © 2017 John Wiley & Sons, Ltd.

ABSTRACT. We present a set of new volume scaling relationships specific to Svalbard glaciers, derived from a sample of 60 volume-area pairs. Glacier volumes are computed from ground-penetrating radar (GPR)-retrieved ice thickness measurements, which have been compiled from different sources for this study. The most precise scaling models, in terms of lowest cross-validation errors, are obtained using a multivariate approach where, in addition to glacier area, glacier length and elevation range are also used as predictors. Using this multivariate scaling approach, together with the Randolph Glacier Inventory V3.2 for Svalbard and Jan Mayen, we obtain a regional volume estimate of 6700 AE AE 835 km 3 , or 17 AE 2 mm of sea-level equivalent (SLE). This result lies in the mid-to low range of recently published estimates, which show values as varied as 13 and 24 mm SLE. We assess the sensitivity of the scaling exponents to glacier characteristics such as size, aspect ratio and average slope, and find that the volume of steep-slope and cirque-type glaciers is not very sensitive to changes in glacier area.

In this study, we assess the accuracy and precision of digital elevation models (DEM) retrieved from aerial photographs taken in 2011 and from Very High Resolution satellite images (WorldView-2 and Pléiades) from the period 2012–2017. Additionally, the accuracy of the freely available Strip product of ArcticDEM was verified. We use the DEMs to characterize geometry changes over Hansbreen and Hornbreen, two tidewater glaciers in southern Spitsbergen, Svalbard. The satellite-based DEMs from WorldView-2 and Pléiades stereo pairs were processed using the Rational Function Model (RFM) without and with one ground control point. The elevation quality of the DEMs over glacierized areas was validated with in situ data: static differential GPS survey of mass balance stakes and GPS kinematic data acquired during ground penetrating radar survey. Results demonstrate the usefulness of the analyzed sources of DEMs for estimation of the total geodetic mass balance of the Svalbard glaciers. DEM accuracy is sufficient to investigate glacier surface elevation changes above 1 m. Strips from the ArcticDEM are generally precise, but some of them showed gross errors and need to be handled with caution. The surface of Hansbreen and Hornbreen has been lowering in recent years. The average annual elevation changes for Hansbreen were more negative in the period 2015–2017 (−2.4 m a−1) than in the period 2011–2015 (−1.7 m a−1). The average annual elevation changes over the studied area of Hornbreen for the period 2012–2017 amounted to −1.6 m a−1. The geodetic mass balance for Hansbreen was more negative than the climatic mass balance estimated using the mass budget method, probably due to underestimation of the ice discharge. From 2011 to 2017, Hansbreen lost on average over 1% of its volume each year. Such a high rate of relative loss illustrates how fast these glaciers are responding to climate change.

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