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High-resolution ice thickness and bed topography of a land-terminating section of the Greenland Ice Sheet
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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2014 (English)In: Earth System Science Data, ISSN 1866-3508, E-ISSN 1866-3516, Vol. 6, no 2, 331-338 p.Article in journal (Refereed) Published
Abstract [en]

We present ice thickness and bed topography maps with a high spatial resolution (250–500 m) of a land-terminating section of the Greenland Ice Sheet derived from ground-based and airborne radar surveys. The data have a total area of ~12 000 km2 and cover the whole ablation area of the outlet glaciers of Isunnguata Sermia, Russell, Leverett, Ørkendalen and Isorlersuup up to the long-term mass balance equilibrium line altitude at ~1600 m above sea level. The bed topography shows highly variable subglacial trough systems, and the trough of Isunnguata Sermia Glacier is overdeepened and reaches an elevation of ~500 m below sea level. The ice surface is smooth and only reflects the bedrock topography in a subtle way, resulting in a highly variable ice thickness. The southern part of our study area consists of higher bed elevations compared to the northern part. The compiled data sets of ground-based and airborne radar surveys cover one of the most studied regions of the Greenland Ice Sheet and can be valuable for detailed studies of ice sheet dynamics and hydrology. The combined data set is freely available at doi:10.1594/pangaea.830314.

Place, publisher, year, edition, pages
2014. Vol. 6, no 2, 331-338 p.
National Category
Physical Geography
Research subject
Earth Science with specialization in Physical Geography
Identifiers
URN: urn:nbn:se:uu:diva-233536DOI: 10.5194/essd-6-331-2014ISI: 000356933900005OAI: oai:DiVA.org:uu-233536DiVA: diva2:753139
Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Hydrology and Bed Topography of the Greenland Ice Sheet: Last known surroundings
Open this publication in new window or tab >>Hydrology and Bed Topography of the Greenland Ice Sheet: Last known surroundings
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The increased temperatures in the Arctic accelerate the loss of land based ice stored in glaciers. The Greenland Ice Sheet is the largest ice mass in the Northern Hemisphere and holds ~10% of all the freshwater on Earth, equivalent to ~7 metres of global sea level rise. A few decades ago, the mass balance of the Greenland Ice Sheet was poorly known and assumed to have little impact on global sea level rise. The development of regional climate models and remote sensing of the ice sheet during the past decade have revealed a significant mass loss. To monitor how the Greenland Ice Sheet will affect sea levels in the future requires understanding the physical processes that govern its mass balance and movement. In the southeastern and central western regions, mass loss is dominated by the dynamic behaviour of ice streams calving into the ocean. Changes in surface mass balance dominate mass loss from the Greenland Ice Sheet in the central northern, southwestern and northeastern regions. Little is known about what the hydrological system looks like beneath the ice sheet; how well the hydrological system is developed decides the water’s impact on ice movement. In this thesis, I have focused on radar sounding measurements to map the subglacial topography in detail for a land-terminating section of the western Greenland Ice Sheet. This knowledge is a critical prerequisite for any subglacial hydrological modelling. Using the high-resolution ice thickness and bed topography data, I have made the following specific studies: First, I have analysed the geological setting and glaciological history of the region by comparing proglacial and subglacial spectral roughness. Second, I have analysed the subglacial water drainage routing and revealed a potential for subglacial water piracy between adjacent subglacial water catchments with changes in the subglacial water pressure regime. Finally, I have looked in more detail into englacial features that are commonly observed in radar sounding data from western Greenland. In all, the thesis highlights the need not only for accurate high-resolution subglacial digital elevation models, but also for regionally optimised interpolation when conducting detailed hydrological studies of the Greenland Ice Sheet.

Abstract [sv]

De ökade temperaturerna i Arktis påskyndar förlusten av landbaserad is lagrad i glaciärer och permafrost. Grönlands inlandsis är den största ismassan på norra halvklotet och lagrar ca 10% av allt sötvatten på jorden, vilket motsvarar ca 7 meter global havsnivåhöjning. För ett par decennier sedan var inlandsisens massbalans dåligt känd och antogs ha liten inverkan på dagens havsnivåhöjning. Utvecklingen av regionala klimatmodeller och satellitbaserad fjärranalys av inlandsisen har under de senaste decenniet påvisat en betydande massförlust. För att förutse vilken inverkan inlandsisen har på framtida havsnivåhöjningar krävs en förståelse för de fysikaliska processerna som styr dess massbalans och isrörelse. I de sydöstra och centrala västra delarna av inlandsisen domineras massförlusten av dynamiska processer i isströmmar som kalvar ut i havet. Massförlusten i de centrala norra, sydvästra och nordöstra delarna domineras av isytans massbalans. Ytterst lite är känt om hur det hydrologiska systemet ser ut under inlandsisen; hur väl det hydrologiska systemet är utvecklat avgör vattnets påverkan på isrörelsen. I denna doktorsavhandling har jag använt markbaserade radarmätningar för att kartlägga den subglaciala topografin för en del av den västra landbaserade inlandsisen. Denna kunskap är en viktig förutsättning för att kunna modellera den subglaciala hydrologin. Med hjälp av rumsligt högupplöst data över istjockleken och bottentopografin har jag gjort följande specifika studier: Först har jag analyserat de geologiska och glaciologiska förhållandena i regionen genom att jämföra proglacial och subglacial spektralanalys av terrängens ytojämnheter. Sedan har jag analyserat den subglaciala vattenavrinningen och påvisat en potential för att avrinningsområdena kan ändras beroende på vattentryckförhållandena på botten. Slutligen har jag tittat mer i detalj på englaciala radarstrukturer som ofta observerats i radardata från västra Grönland. Sammanfattningsvis belyser avhandlingen behovet av inte bara noggranna rumsligt högupplösta subglaciala digitala höjdmodeller, utan även regionalt optimerad interpolering när detaljerade hydrologiska studier ska utföras på Grönlands inlandsis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 59 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1265
Keyword
climate change, Greenland Ice Sheet, radio-echo sounding, digital elevation models, ice thickness, bed topography, spectral analysis, roughness, subglacial hydrology, water piracy, englacial features, drainage catchments, meltwater runoff, ice dynamics, klimatförändringar, Grönlands inlandsis, markbaserad radar, digitala höjdmodeller, istjocklek, bottentopografi, spektralanalys, subglacial hydrologi, englaciala strukturer, avrinningsområden, isdynamik
National Category
Physical Geography
Identifiers
urn:nbn:se:uu:diva-259076 (URN)978-91-554-9280-9 (ISBN)
Public defence
2015-09-11, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2015-08-20 Created: 2015-07-26 Last updated: 2016-02-12

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