Estimating snow accumulation on Mýrdalsjökull and Öræfajökull with snow radar using Discrete Gabor Transform for image analysis. Implications to the mass balance of ice cauldrons.

• Main Author: Krista Hannesdóttir 1980-
• Other Authors: Háskóli Íslands
• Format: Thesis
• Language: English
• Published: 2021
• Subjects: Jarðeðlisfræði; Glugga; Mýrdalsjökull
• Online Access: http://hdl.handle.net/1946/37563

Ice cauldrons on Mýrdalsjökull were surveyed in 2016 and 2018 with high frequency 500 MHz Ground Penetrating Radar (GPR) and the measurements analyzed with the aid of in-situ snow core measurements. Similarly in 2018 a GPR survey was performed on Öræfajökull after the formation of a cauldron inside the Öræfajökull caldera in 2017. The survey data was processed with Discrete Gabor Transform (DGT) and filtered out the frequency magnitude with a Hamming window. A interface in Octave was implemented to assist in tracing snow thickness profiles. A map of the snow thickness distribution was interpolated from the traced snow thickness profiles. The distribution showed additional accumulation of snow thickness due to snowdrift in cauldrons on Mýrdalsjökull. The energy required to melt additional accumulation in cauldrons in 2016 corresponds to annual power of ~15 MW. This is a insignificant excess power compared to a study by Jarosch et al. 2020, where the power of the geothermal areas below the cauldrons was estimated ~600 MW. DGT processing determined two possible horizons from autumn 2017 in Öræfajökull GPR data. Previous interpretation of autumn layer in six snow cores drilled within the study area in 2018 was not consistent with either of these horizons; some fitted the lower and some the upper. Precipitation measured near the glacier strongly indicate the lower layer was the autumn horizon (summer surface). An east to west gradient from 12.5 m to 10.0 m in the autumn horizon across the Öræfajökull caldera was in agreement with a weather model with most of the precipitation falling on Öræfajökull peak during easterly winds. Snjósöfnun í sigkötlum Mýrdalsjökuls og nágrenni þeirra var rannsökuð með 500 MHz snjósjá- og snjókjarnamælingum, vorið 2016 og 2018 . Sambærileg könnun var gerð 2018 eftir tilkomu sigketils innan öskju Öræfajökuls árið 2017. Snjósjágögnin voru meðhöndluð með Strjálu Gabor Vörpuninni (SGV) og síuðu út tíðnistyrk með Hamming glugga. Viðmót í Octave var forritað til að auðvelda teiknun ...