Kartläggning av palsars inre struktur med hjälp av georadarteknik, i Vissátvuopmi, Sverige

Abstract

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.