PhD defence: Mikkel Toft Hornum

Mikkel Toft Hornum defends his thesis,

Groundwater springs in continuous permafrost

Associate Professor Ylva Sjöberg, IGN
Professor Aart Kroon, IGN
Professor Andy Hodson, the University Centre in Svalbard

Assessment Committee:
Senior researcher Jolanta Kazmierczak, GEUS
Associate Professor Moritz Langer, Univ. of Amsterdam
Professor Bo Elberling (chair), IGN

In the cold regions of the Earth, the subsurface is frozen in a state called permafrost. Since fluids cannot flow through ice, the permafrost traps deep groundwater and solutes such as greenhouse gases. In some locations, groundwater springs perforate the permafrost and allow groundwater to reach the surface and atmosphere. Several unanswered questions remain about the mechanisms that drive these groundwaters springs and about the landscape features that are favorable for their formation. In this thesis, some of these unanswered questions are addressed using methods that range from direct field measurements to advanced computational modelling tools. The key findings are the following. First, a new model for driving groundwater spring outflow in continuous permafrost areas is formulated, shown to be viable, and its significance is quantified. Second, we find that groundwater can use fractures within the glacial landscape relief as a pathway for flowing through permafrost. Thirdly, the discovery of groundwater springs in Greenland is reported on, and we argue that they represent a previously unknown mechanism of perennial meltwater routing from the Greenland ice sheet.

A digital version of the PhD thesis can be obtained from the PhD secretary