A plot-scale study of firn stratigraphy at Lomonosovfonna, Svalbard, using ice cores, borehole video and GPR surveys in 2012–14

Abstract

ABSTRACT. Spatial heterogeneity of snow and firn properties on glaciers introduces uncertainty in interpretation of point and profile observations and complicates modelling of meltwater percolation and runoff. Here we present a study of the temporal and spatial dynamics of firn density and stratigraphy at the plot-scale (≈10 m × 10 m × 10 m) repeated annually during 2012-14 at the Lomonosovfonna icefield, Svalbard. Results from cores, video inspections in boreholes and radar grid surveys are compared. Ice layers 0.1-50 cm thick comprised ≈8% of the borehole length. Most of them are 1-3 cm thick and could not be traced between boreholes separated by 3 m. Large lateral variability of firn structure affects representativeness of observations in single holes and calls for repeated studies in multiple points to derive a representative stratigraphy signal. Radar reflections are poorly correlated with ice layers in individual boreholes. However, the match between the high amplitude peaks in the grid-averaged radar signal and horizons of preferential ice layer formation revealed by averaging the video surveys over multiple boreholes is higher. These horizons are interpreted as buried firn layers previously exposed to meltfreeze or wind-driven densification and several of them are consistently recovered throughout three field campaigns.

Parameterizing Deep Water Percolation Improves Subsurface Temperature Simulations by a Multilayer Firn Model

“…Referenced to the glacier surface in April 2014 these depths correspond to 7, 9.1, and 11.3 m. The phenomena can be related to perched horizons with increased water content that have a horizontal extent less than the plot covered by our thermistor measurements (6×6 m). In April 2014 Marchenko et al (2017) found multiple ice layers at 7, 8, 9, and 10.8 m depth in three boreholes where the thermistor strings used in present study were installed afterwards. These ice layers could have acted as impermeable horizons and retained water which locally inhibited the cold wave penetration.…”

“…yr −1 (Van Pelt et al, 2014;Wendl et al, 2015). Subsurface temperature measurements at Lomonosovfonna during summer season were carried out in 1965 (Zinger et al, 1966), 1980(Zagorodnov and Zotikov, 1980, and more recently by Marchenko et al (2017). While in Marchenko et al (2017) the focus was on subsurface density and stratigraphy, in this study the analysis concentrates on the subsurface temperature evolution.…”

“…Winter accumulation rate measurements include the effect of snow settling that occurs above the previous summer surface and Lomonosovfonna and its outlet glaciers. Green dots show locations of the WRF domain nodes; large red dot marks location of the AWS and thermistor strings (detailed sketch of installation is found in Marchenko et al, 2017: thermistor strings were installed in boreholes 1-9); smaller red dots show the WRF domain node, output for which was used to force the surface energy balance model and location of the stake S11. Background -true color satellite image LANDSAT ETM+ from 13 July 2002, contour lines and coastline data is provided by the Norwegian Polar Institute.…”

“…The lengths of the cores were 9.9, 11.3 and 13.6 m. Details on the routines applied for extraction and processing of the cores were presented by Marchenko et al (2017). For the further analysis the density profiles originally measured with a high vertical resolution were smoothed using a 1 m running average filter to exclude spikes caused by thin and likely not laterally consistent ice layers (Marchenko et al, 2017) and to ensure mass conservation.…”

Dynamic Response of a High Arctic Glacier to Melt and Runoff Variations

“…The front of Nordenskiöldbreen has retreated by 15-35 m/a since the end of the Little Ice Age, but retreat rates have been negligible since ∼2002 as the glacier is retreating on land (Allaart, 2016;Rachlewicz et al, 2007). Nordenskiöldbreen is a polythermal glacier ("type b" in Blatter & Hutter, 1991), with temperate conditions in the accumulation zone due to deep meltwater percolation and refreezing (Marchenko et al, 2016(Marchenko et al, , 2017Vega et al, 2016), and cold near-surface ice in the ablation area (Van Pelt et al, 2012). Nordenskiöldbreen is a polythermal glacier ("type b" in Blatter & Hutter, 1991), with temperate conditions in the accumulation zone due to deep meltwater percolation and refreezing (Marchenko et al, 2016(Marchenko et al, , 2017Vega et al, 2016), and cold near-surface ice in the ablation area (Van Pelt et al, 2012).…”