Háskóli Íslands

On Thursday 9th of February  Skafti Brynjólfsson will present his Ph.D. thesis in Earth Sciences.

The thesis is titled Dynamics and glacial history of the Drangajökull ice cap, Northwest Iceland.

The Ph.D. studies were conducted under a joint degree agreement between the University of Iceland and the Norwegian University of Science and Technology. The thesis was defended in Norway on September 24th 2015.

Opponents were Dr. Nicolaj K. Larsen, Associate Professor at the Department of Geoscience, Aarhus University,  and Professor at the University of Copenhagen, Denmark, and Dr. Armelle Decaulne, Research Geologist at the Laboratoire Géolittomer, University of Nantes, France.

The supervisors were Dr. Ólafur Ingólfsson, Professor at the Faculty of Earth Sciences, University of Iceland, Dr. Anders Schomacker, Professor at UiT The Arctic University of Norway and Associate professor at the University of Copenhagen, Denmark, and Dr. Achim Beylich, Research Scientist at the the Geological Survey of Norway.

The assessment committee included Dr. Bjørge Brattli, Professor at the Department of Geology and Mineral Resources Engineering, The Norwegian University of Science and Technology, Dr. Nicolaj K. Larsen,  Associate Professor at the Department of Geoscience, Aarhus University, Denmark, and Dr.  Armelle Decaulne, Research Geologist at the Laboratoire Géolittomer, University of Nantes, France.

Abstract

This thesis describes the glacial history, glacier dynamics, sediments and landforms of the Drangajökull ice cap as well as the glacial history and dynamics of the eastern Vestfirðir peninsula in northwest Iceland from the Late Weichselian until present. The aim was to reconstruct and improve the present understanding of the glacial history, surge history and dynamics of the Drangajökull ice cap. 

The results reveal a topographically controlled ice sheet which more and less covered the Vestfirðir peninsula during the last glaciation. Cold-based non-erosive sectors of the ice sheet covered most of the mountains while fjords and valleys were occupied by dynamical, warm-based ice. Ice thinning and deglaciation started over the mountain plateaux ca. 26 ka BP; the deglaciation was stepwise and asynchronous, uplands and some valleys were deglaciated 14-15 ka BP while valleys draining the main outlets of Drangajökull were occupied by outlet glaciers until c. 9 ka BP. 

The forefields proximal to the present Drangajökull ice cap are characterised by thin, coarse grained till and locally weathered bedrock, except for the sandur covered valley floors. The landforms mapped at the surging outlet glaciers are not unique for surging glaciers, and furthermore the mapped landform assemblage does not resemble landsystem models for surging glaciers.

The surge-type outlets of Drangajökull reached their LIA maximum extent asynchronously during surges in the period ca. 1700-1846 AD. Review of historical data and geomorphological mapping revealed twice as many surges than previously recorded. The surge interval varies from 10-140 years between and within the outlets. Surges were most frequent during the 19th century and the earliest 20th century. No clear relationship between surge initiation or periodicity and climate could be established. A distinct ice discharge occurs during surges, reflected in 10-30 m surface thinning of the upper reservoir areas and 10-120 m thickening of the receiving areas. During the present quiescent phase, the reservoir areas thicken by c. 0.5-0.7 m a-1 and the receiving areas thin by c. 1 m a-1, which might bring the glacier surface to a pre-surge stage in 45-65 years.

Future studies could focus on extensive morphological mapping and direct dating of glacial features, aiming to add further details to the glacial history and test the reconstructions of Drangajökull presented here. Further investigation of the surge-type glaciers, e.g. extensive monitoring of weather and the glacier conditions, geophysical surveys both of the glaciers and their forefields, might also contribute to an improved understanding of the Drangajökull surging glaciers. 

About the doctoral candidate

Skafti Brynjólfsson was born in 1982. He graduated from Akureyri Junior College in 2003, and concluded his BSc. and MSc. degrees in geology from the University of Iceland in 2007 and 2009, respectively. He earned his PhD. as a joint degree from The University of Iceland and the Norwegian University of Science and Technology (NTNU).

Skafti has been employed at the Icelandic Institute of Natural History since 2009 and works there at present.

He is married to Lára Betty Harðardóttir and they have three children, Jóhanna, Hörður Högni and Freyja.

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