During the last ice age, some 28 - 9 000 years ago, large ice sheets covered massive areas of all over the globe. Much of northern Europe was glaciated and covered by a large ice sheet known as the Fennoscandian Ice Sheet. How this ice grew and shrank, and ultimately retreated and disappeared, is still partly unknown.
“There are many gaps in our knowledge with regards to this topic,” PhD candidate Artūrs Putniņš says.
He has reconstructed the evolution and retreat of the ice sheet during the Last Ice Age in Gausdal Vestfjell, south-central Norway.
Understanding evolution and deglaciation
“The goal of my work has been to improve the general understanding of the evolution and deglaciation of the former Fennoscandian Ice Sheet during the Last Ice Age at a part of its inner region.”
To achieve this, he has used the latest remote sensing and spatial data applicable for glacial reconstructions. LiDAR (airbone laserscanning) datasets provided by the Norwegian Mapping Authority (Kartverket) has been one of the main base source of information for mapping the landforms.
Step by step
Artūrs’ results showed that the glacial evolution has been stepwise.
“A topography independent ice flow is followed by a regional flow phase,” he explains.
These two phases have subsequently been replaced by a strongly channelized, topography-driven ice flow phase which can be divided into several substages. Prior to the ice disintegration, ice flow was increasingly confined into valleys.
“It is likely that these flows were separated by colder, less active ice.”
The deglaciation is characterised by a vertical down-melting of ice, dynamic evolution of the meltwater drainage systems that included temporary ice-dammed lakes and spillways, and deposition of various glacifluvial landforms.
Landforms in Gausdal Vestfjell
The work conducted within Artūrs’ thesis contains a geomorphological data set of more than 17 000 glacial and glacifluvial landforms in Gausdal Vestfjell, south-central Norway. This geological record reveals the evolution of ice flow pattern and retreat of the former Fennoscandian Ice Sheet.
The constraints of GIS
Furthermore, part of Artūrs’ work has been to explore the possibilities and constraints of Geographical Information Systems (GIS) tools and how new approaches can be implemented and used to improve the efficiency of data collection and analyses used for glacial reconstructions.
“I have explored new ways of recognizing and extracting digital elevation models, DEMs, in a semi-automated manner.”
Increasing mapping efficiency
“Part of my thesis explored the semi-automated mapping techniques, or ‘SAM’, that may be a reliable and effective alternative for data extraction used instead of the manual mapping of landforms which is time consuming and potentially subjective.”
Several SAM methods are proposed for glacial streamlined landform extraction, yet none was considered optimal for the extraction of glacial ice flow directions in a complex terrain, such as the study area in the Scandinavian Mountains. Therefore, the potential of the grayscale thinning (skeletonisation) application for the extraction of directional trends from the terrains is explored.
In addition, Artūrs used GIS tools to introduce a simple, vertically adjustable reference surface gradient (‘virtual ice surface’) representing vertical down-wasting of ice.
“This makes it possible to distinguish several important ice marginal positions and to reconstruct significant deglaciation events in greater detail than before.”
He further explains that this approach has a potential to be further used to reduce the uncertainties in spatial and temporal correlations of meltwater landforms that is a valuable source of information on the dynamics of past ice sheets, yet, due to correlation difficulties, often have only a secondary role in establishing glacial reconstructions.
From past to future
By using the latest available technology and methods, Artūrs has provided detailed glacial reconstructions on how the deglaciation of the last ice sheet was driven by warming climate. The results from his thesis may improve our prediction on the future ice sheets development and climate change.
“By understanding the past, our understanding on present processes and projection on future glacial ice loss and climate change will improve.”