Disputas - Master of Science Lis Allaart
Master of Science Lis Allaart will Thursday March 25th at 15:15 publically defend her thesis for the PhD degree in Science
Title of the thesis:
«Late Pleistocene-Holocene history of Svalbard ice caps and glaciers – integrating marine, terrestrial and lacustrine archives»
Popular scientific abstract:Svalbard is located right at the border between the last arm of the warm Gulf Stream and the cold Arctic Ocean. The glaciers in the archipelago are very sensitive to even small changes in the climate system, and Svalbard is therefore a good location to study how glaciers acted to past climate variability.
The climate in the northern hemisphere was naturally warmer c. 10,000 years ago, due to changes in the Earth’s orbit around the sun as well as changes in the tilt of the axis of the Earth. These natural orbital changes should today lead towards a colder climate, however, the anthropogenic induced global warming is a fact and the climate is actually getting warmer. Studying how glaciers in Svalbard acted to the natural warmth c. 10,000 years ago, can help to shed light on how they will act to modern global warming today.
Weather data measured with instruments extend back only about 150 years. To get to know more about natural climate variability, longer climate records are needed. To figure out how climate varied earlier than 150 years ago, climate archives such as ice cores can be used. Lakes and fjords are also excellent climate archives. Over time, sediment (i.e., clay, silt, sand, gravel) accumulates in layers at the lake and fjord floors, and each layer holds information about the time when it was deposited. If one is lucky, plant and animal remnants can be found in the layers, used for radiocarbon dating and thus tell how old each layer is.
The climate archives of the northern part of Wijdefjorden and the adjacent lake, Femmilsjøen, in northern Svalbard were collected during the summers of 2017 and 2018. Plastic tubes were penetrated into the sea and lake floors and the layers of sediment were brought back to Tromsø inside the sediment tubes. Information about the sediment layers below the sea and lake floors were also collected by sending sound waves into the sediments. The landscape surrounding the lake was also mapped. The plastic tubes full of sediments were analysed in the laboratory in Tromsø. Based on all the material, the glacial history of the past c. 16,000 years of the area was reconstructed. Additionally, a review paper about the glacial history the past 12,000 years of all of Svalbard is included in this dissertation.
During the Last Glacial, the study area in northern Svalbard was covered by a thick ice sheet that left glacial stripes and other traces on the fjord floor. The area deglaciated early, maybe as early as 16,000 years ago. Seawater temperatures and sea-ice extent fluctuated during the deglaciation. Femmilsjøen was due land rise after the retreat of the ice separated from the fjord c. 11,400 years ago. The ice cap, Åsgardfonna, which is responsible for most of the meltwater running into Femmilsjøen, were completely absent or a lot smaller than today from 10,100 to 3,200 years ago. The glaciers in the region started growing again c. 3,200 years ago, when it was getting colder again. Today the glaciers in Svalbard are receding with high rates.
The thesis is published in Munin and is available at: https://munin.uit.no/handle/10037/20634
- Professor Anders Schomacker, Department of Geosciences, UiT (main supervisor)
- Professor Matthias Forwick, Department of Geosciences, UiT
- Associate Professor Lena Håkansson, UNIS (external)
- Professor Michael Retelle, Bates College / UNIS (external)
- Professor Jason P. Briner, Department of Geology, University at Buffalo, USA (1. Opponent)
- Senior Researcher Katrine Husum, Norwegian Polarinstitute (2. Opponent)
- Professor Jan Sverre Laberg, Department of Geosciences, UiT (internal member and leader of the committee)
All members will participate remotely to the defence.
Leader of the public defense:
The leader of the public defense is Professor Alfred Hanssen , Vice-Dean Innovation, Faculty of Science and Technology, UiT.
Opposition ex auditorio:
If you have any questions for the candidate during the public defence, please send an e-mail to the leader of the public defence. They will announce the questions during the defence.
The trial lecture is held Thursday March 25th at 13:15 digitally.
Title of the trial lecture: «Evidence for and against a glacier re-advance in the Arctic during the Younger Dryas»
The defense and trial lecture will be streamed via Mediasite:
All audience are to use mediasite to view the defence.