Mass balance, ice volume, and flow velocity of the Vestre Grønfjordbreen (Svalbard) from 2013/14 to 2019/20

The intra-annual variability of the surface ice ablation on the 5.5 km2 Aldegondabreen glacier (Spitsbergen Island, Barentsburg area) is presented. The ice ablation was measured during five seasons (2018–2022) at the two stakes, installed in the lower part of the glacier and at the index site, where the amount of ablation numerically coincides with the glacier-averaged value with the r = 0.99 agreement. The temporal resolution of the ice ablation data is uneven and varies from 3 to 45 days. To carry out the correlation analysis, meteorological data from the automated weather station located near the glacier terminus are used. The ice ablation rates, obtained after normalization for the number of days between stake readings, have a tight correlation with both the air temperature and the downwelling shortwave radiation flux for most of the seasons, in 2018–2021 (r = 0.71–0.99). Surface air temperature and short-wave radiation are closely related; the above estimates indicate the leading role of short-wave radiation in the summer ablation of the glacier in the period 2018–2021. The year 2022 became anomalous, as the correlation with the shortwave radiation significantly decreased (r = 0.21–0.34). The European heat wave of 2022, which also affected the Svalbard archipelago, interrupted the ordinary intra-annual variability of the air temperature, causing the unprecedented ice melt on Aldegondabreen in September. The predicted increase in frequency and intensity of the future heat waves will result in an increased role of turbulent fluxes in the surface energy balance of the low-elevated Svalbard glaciers. The article demonstrates how the empirically identified dependencies can change from season to season in a non-stationary climate.

Intra-Annual Variability of the Surface Ablation of the Aldegondabreen Glacier (Spitsbergen)

Prokhorova,

Terekhov,

Demidov

et al. 2023

Uncertainty Assessment for Mean Snow Cover Depth Derived from Direct Measurements on Aldegondabreen Glacier (Svalbard)

Terekhov,

Vasilevich,

Prokhorova

2023

Received March 27, 2022; revised May 5, 2023; accepted June 27, 2023This study introduces an empirical equation allowing to estimate an uncertainty of area-averaged snow depth on the Aldegondabreen Glacier, computed from standard snow surveys and made by an avalanche probe or by similar equipment. The two-decade history of the ongoing mass-balance monitoring program on this glacier shows that the methodology of field work on snow-measuring survey varies somewhat from year to year: the number and location of measurement points change. To identify and quantify long-term trends and variations in snow cover, it is crucial to assess the inter-comparability of the data in the obtained measurement series. The proposed equation was intended to solve this task basing on the collected data only, allowing to estimate the uncertainty even retrospectively. To build this equation, we applied a bootstrap statistical approach to the results of snow surveys carried out in Svalbard in 2015–2021. After interpolating the field measurements, obtained rasters were sampled sequentially with different numbers of points, simulating the real snow survey. The points were initially located in a form of a quasiregular grid and then randomly shifted between the iterations. After a thousand simulations for each number of points, the standard deviations were calculated relative to the “true” values, derived from corresponding rasters. These standard deviations, which we admit to be a random error of the area-averaged snow depth value, expectedly decrease with the number of sampling points and increase with the coefficient of variation (\({{{\text{C}}}_{\user1{v}}}\)). The well-known \({{{\text{C}}}_{\user1{v}}}\) index indirectly characterizes the irregularity of snow cover. After approximating the bootstrap results, the authors derived an equation that yields a relative error. The equation includes only two predictors which are the probing density per area unit and the \({{{\text{C}}}_{\user1{v}}}\), which potentially allows using it for the other glaciers. However, the universality of the empirically obtained coefficients is debatable, since they may vary due toa glacier size, its morphology and other parameters.

The influence of spatial variability of solar radiation on the mass balance of glaciers in the Grønfjorden Bay area (the Svalbard archipelago)

Terekhov,

Prokhorova,

Demidov

2024

In this article, we investigate how the irregular insolation of two low-elevated Svalbard glaciers exerts effect on rates of their surface melting. We compare the spatial distribution of rates of the surface lowering of glaciers Vøringbreen (0.76 km2) and Aldegondabreen (5.5 km2), both are located near Barentsburg settlement in the western part of Nordenskiöld Land (the Spitsbergen Island). As an approximation of the solar radiation flux, we used the potential incoming solar radiation calculated by the ArcticDEM digital elevation model for the period July 15–September 15, which is a typical time of ice ablation in the region under consideration. Motions of both glaciers are extremely slow, which allows assuming that lowering of their surfaces are identical to the rates of surface melting. We have found that both glaciers are distinctly divided into two parts, more and less sunlit. The spatial pattern of insolation of the Vøringbreen glacier is controlled by the shading of the walls surrounding the cirque, while the Aldegondabreen one due to its concave shape has two different areas with a more southern and more northern exposure. The lowering of the surface shows that the more and less illuminated parts differ significantly in ice ablation. The maximum differences in melting caused by the irregular insolation are 2.1 m of ice depth over five years for the Aldegondabreen Glacier (2008–2013 and 2013–2018) and 2.2 m over six years for the Vøringbreen Glacier (2013–2019), that is 40, 30 and 25% of the total values of the surface depression for the corresponding periods. Within every 50-meter altitude interval, correlation coefficients between surface ablation and insolation vary from –0.33 to –0.62 for the Aldegondabreen and from –0.50 to –0.92 for the Vøringbreen glacier. When compared with the vertical gradient of the ice melting, the variability of ablation caused by the irregular insolation correspond to a difference in altitudes of 45–50 m in vertical for the Aldegondabreen and 60 m for Vøringbreen. These values are significant taking into account the small altitudinal range of the glaciers in that part of Spitsbergen.