Browsing by Author "Cederbrant, Julia"

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Kartläggning av palsars inre struktur med hjälp av georadarteknik, i Vissátvuopmi, Sverige
(2019-10-30) Cederbrant, Julia; Wing, Cornelia; University of Gothenburg/Department of Earth Sciences; Göteborgs universitet/Institutionen för geovetenskaper
Palsas are unique features limited to the boundaries of the Arctic, where a frozen core through ice segregation and buoyancy forces an uplift in peat mires. The area of palsas in the world is decreasing and the EU has named palsa mires one of the most threatened environments. To fully understand the connection between degradation of palsas and climate change, more documentation of the inner structure is needed. The aim of this project is to investigate the inner structure of palsas and their degradation in Vissátvuopmi through ground penetrating radar (GPR). Antennas with different MHz frequencies are used to evaluate how layers in two selected palsas appear and with which frequency they are distinguishable. Previous research has been using only one antenna which have led to limitations in the interpretation of the materials. Radargrams along several profiles on the palsas were created through the GPR investigation and interpreted in two steps. Reflectors were marked on the radargram and an interpretation was made based upon previous research and knowledge about the area. Layers of snow, peat, silty glaciolacustrine sediments, ice lenses, morain, ground frost and permafrost were visible in the radargrams depending on the resolution of the antenna. The antenna with 800 MHz showed snow and peat in a good way but to clearly see the inner structure of a palsa a combination of 500 MHz and 250 MHz is favorable. The GPR survey combined with degradational patterns showed that the two palsas are in a mature stage where they have begun to collapse. The two palsas have been degraded at a faster pace than other palsas in Vissátvuopmi where the palsa plateau have been slightly more degraded and in a faster pace than the palsa dome. In a disadvantageous climate for palsa formation, palsas are at risk of disappearing in the future.
The cooling potential of Rain Gardens and Green Roofs - The influence on energy partitioning in Kvillebäcken, Gothenburg
(2021-07-05) Cederbrant, Julia; University of Gothenburg/Department of Earth Sciences; Göteborgs universitet/Institutionen för geovetenskaper
Blue-green infrastructure (BGI) has become a popular way of combating the effects of climate change, both regarding heat mitigation and runoff from precipitation. This thesis aims to understand the potential of two BGI types, namely rain gardens and green roofs, of increasing the latent heat fraction in an urban area and thereby also understand the possible cooling effect from these measures. Rain gardens and green roofs are further compared to the effect on energy partitioning of high albedo roofs and an increased surface fraction of grass in the Kvillebäcken area in Gothenburg. The thesis was performed using an energy and water balance model called SUEWS in order to investigate heat and water fluxes. Scenarios of increased rain garden and green roof surface coverage was used to model the influence on latent and sensible heat fluxes. Results show that both rain gardens and green roofs have potential to increase latent heat and thereby reduce temperatures. However, both BGI-solutions increase latent heat during periods of frequent precipitation and not when it is needed the most, that is during heatwaves and periods of strong Urban Heat Island (UHI). Increasing grass areas have a larger effect than other BGI but is commonly outcompeted in urban areas due to lack of space, making it a less attractive option in densely built areas. During dry and hot periods, it was found that high albedo roofs have the largest potential to decrease temperatures, however through a reduction of sensible heat. The study concludes that water availability is crucial for BGI to increase latent heat, as water needs to be frequently added for maximum efficiency. To combine the varied benefits of BGI with high albedo surfaces should therefore give the largest effect on cooling the urban climate.