Snow Thickness on Austre Grønfjordbreen, Svalbard, From Radar Measurements and Standard Snow Surveys

Abstract

Comparison of two methods of measurements of snow cover thickness on the glacier Austre Grønfjordbreen, Svalbard was performed in the spring of 2014. These methods were the radar (500 MHz) observations and standard snow surveys. Measurements were conducted in 77 different points on the surface of the glacier. A good correlation (R 2 = 0.98) was revealed. In comparison with the data of snow surveys, the radar measurements show a similar but more detailed pattern of the distribution of the snow cover depth. The discrepancy between the depths of snow cover on maps plotted from data of both methods did not exceed 30 cm in most parts of the glacier. The standard error of interpolation of the radar data onto the entire glacier surface amounts, on average, to 18 cm. This corresponds to the error of radar measurements of 18.8% when an average snow depth is about 160 cm and 9.4% at its maximum thickness of 320 cm. The distance between the measurement points at which the spatial covariance of the snow depth disappears falls between 236 and 283 m along the glacier, and between 117 and 165 m across its position. We compared the results of radar measurements of the pulse-delay time of reflections from the base of the snow cover with the data of manual probe measurements at 10 points and direct measurements of snow depth and average density in 12 snow pits. The average speed of radio waves propagation in the snow was determined as V cr = 23.4±0.2 cm ns −1 . This magnitude and the Looyenga and Kovacs formulas allowed estimating the average density of snow cover ρ L = 353.1±13.1 kg m −3 and ρ K = 337.4±12.9 kg m −3 . The difference from average density measured in 12 pits ρ av.meas = 387.4±12.9 kg m −3 amounts to −10.8% and −14.8%. In 2014, according to snow and radar measurements, altitudinal gradient of snow accumulation on the glacier Austre Grønfjordbreen was equal to 0.21 m/100 m, which is smaller than the average values (0.35 m/100 m). According to the results of snow measurements of 2011-2014, the average thickness of the snow cover on the glacier Austre Grønfjordbreen was by 17 cm greater than in 1979. In the very snowy year 2012, it was higher by 21.5 cm in comparison with the year 1979, and its spatial variability (standard deviation σН) had increased by 25.6 cm. Estimates of spatial and temporal variability of snow cover depth will be used to analyze the hydrothermal state of the glacier and its changes with regard to revealed features and climatic trends.

Retrieval of Spatial and Temporal Variability in Snowpack Depth over Glaciers in Svalbard Using GPR and Spaceborne POLSAR Measurements

“…Results of previous snow surveys on the glacier (1979,(2011)(2012)(2013)(2014) show that the mean snow thickness there varies in range from 140 to 165 cm (0.55 to 0.70 m water equivalent (w.e.)). Ground-based radar (GPR) measurements at 500 MHz of snow cover depth in spring of 2014 showed A close relationship (R 2 = 0.98) with data from manual measurements [8]. Now the firn zone is observed only as small patches at the ice divide and in A small area in the head of the eastern branch.…”

“…To convert two-way travel times of reflected radar waves to snow depths we used our data of snow density measurements in 12 snow pits and Looyenga's formula [31] for heterogeneous mixtures that gives the best estimation compared with other solutions as we found earlier [8]. The averaged mean snow density in snow pits varies from 359 to 580 kg m −3 .…”

“…Snow deposition increases with elevation, but it is also observed that this altitudinal trend is highly variable due to the drifting wind and other local topoclimatological factors in Svalbard. Recent investigations [8][9][10][11][12] suggest that the altitudinal gradient of snow accumulation has decreased, and the average snow thickness on the Austre Grønfjordbreen has increased by 17 cm compared to average snow thickness in 1979. Spatial variability has also increased over the region.…”

“…Hence, continuous monitoring of the spatial and temporal variability of snow cover depth is the need of the hour, which can be used to understand the state of the glacier and the changes and processes taking place in it.An alternative method to field-based manual measurements of snow depth is A ground penetrating radar (GPR) survey. This survey is an optimal technique to provide A spatial profile over large areas for understanding snow depth variability [8,9]. Apart from the spatial variability, snow accumulation and its parameters also change with time which require frequent large area observations to monitor their spatial and temporal variabilities.…”

Mass Balance of Austre Grønfjordbreen, Svalbard, 2006–2020, Estimated by Glaciological, Geodetic and Modeling Aproaches

“…The system was deployed on the glacier surface using a snowmobile. The results of GPR and standard manual snow accumulation surveys along with the comparison of the methods are presented in Lavrentiev et al [17].…”