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Water content of firn at Lomonosovfonna, Svalbard, derived from subsurface temperature measurements
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Uppsala University. (ice and climate)ORCID iD: 0000-0003-4785-4532
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The potential of capillary forces to retain water in pores is an important property of snow and firn at glaciers. Melt water suspended in pores does not contribute to runoff and is likely to refreeze during winter, by this affecting the climatic mass balance. However, retrieving of empirical data on snow/firn water content is challenging due to the subtle balance between the solid and liquid phases of water. Here we use subsurface temperature and density measured at 1200 m a.s.l.: at Lomonosovfonna, Svalbard, to derive water content of the firn profile after the melt season in 2014. For that measured and simulated rates of freezing front propagation are compared. The resulting volumetric volumetric water content of the subsurface profile is ca 1–2.5 vol.% above the depth of 3 m and below 0.5 vol.% below with a prominent lateral variability. These values are considerably lower than what is commonly used in snow/firn models, which is interpreted as a result of preferential water flow at Lomonosovfonna leaving extensive dry pockets in snow/firn above the fingering front. This calls for implementation of preferential flow description in snow/firn models.

National Category
Physical Geography
Identifiers
URN: urn:nbn:se:uu:diva-334153OAI: oai:DiVA.org:uu-334153DiVA: diva2:1158863
Available from: 2017-11-21 Created: 2017-11-21 Last updated: 2017-11-21
In thesis
1. Subsurface fluxes of mass and energy at the accumulation zone of Lomonosovfonna ice cap, Svalbard
Open this publication in new window or tab >>Subsurface fluxes of mass and energy at the accumulation zone of Lomonosovfonna ice cap, Svalbard
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Glaciers cover ca 10% of the Earth's land and are found in the high altitudes and latitudes. They are important components of environmental systems due to the multiple feedbacks linking them with the atmosphere, hydrosphere and periglacial landscapes. The cold sloping surfaces of glaciers change the patterns of atmospheric circulation at different scales and at the same time glaciers are largely controlled by climate. They are commonly used as climatic archives for reconstruction of the past environmental changes based on evidences from the areas affected by glaciation at the moment and in the past. Glaciers are the largest fresh-water reservoirs on our planet and runoff thereof significantly affects the global sea level and life in glaciated catchments. However, melt- and rain-induced runoff from glaciers greatly depends on the subsurface conditions which thus need to be taken into account, particularly in a changing climate.

This thesis focuses on the processes of subsurface mass and energy exchange in the accumulation zones of glaciers, which are largely driven by the climate at the surface. Results are largely based on empirical data from Lomonosovfonna ice cap, Svalbard, collected during field campaigns in 2012-2017. Observations of subsurface density and stratigraphy using shallow cores, video records from boreholes and radar surveys returned detailed descriptions of the snow and firn layering. The subsurface temperature data collected using multiple thermistor strings provided insights into several subsurface processes. The temperature values measured during three summer seasons were used to constrain the suggested parameterization of deep preferential water flow through snow and firn. The part of data recorded during the cold seasons was employed for an inverse modelling exercise resulting in optimized values of effective thermal conductivity of the subsurface profile. These results are then used to compute the subsurface water content by comparing the simulated and measured rates of freezing front propagation after the melt season in 2014.

The field observations and quantitative estimates provide further empirical evidences of preferential water flow in snow/firn packs at glaciers. Results presented in the thesis call for implementation of description of the process in layered models simulating the subsurface fluxes of energy and mass at glaciers. This will result in a better understanding of glacier response to the past and future climatic changes and more accurate estimates of glacier runoff.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. 52 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1601
Keyword
glacier, ice sheet, sea level, runoff, ice, firn, snow, stratigraphy, density, core, radar, thermistor, temperature, preferential water flow, thermal conductivity, water content
National Category
Physical Geography
Research subject
Earth Science with specialization in Physical Geography
Identifiers
urn:nbn:se:uu:diva-334178 (URN)978-91-513-0158-7 (ISBN)
Public defence
2018-01-19, GM128 Axel Hambergsalen, Villavägen 16, Uppsala, 09:00 (English)
Opponent
Supervisors
Projects
Stability and Variations of Arctic Land Ice (SVALI)
Available from: 2017-12-13 Created: 2017-11-21 Last updated: 2017-12-13

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